1

CHAPTER - I

INTRODUCTION

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1 INTRODUCTION

1.1 INTRODUCTION TO CO-ORDINATION CHEMISTRY.

1.2 LIGANDS CONTAINING OXYGEN AND NITROGEN AS

DONOR ATOMS AND THEIR METAL COMPLEXES.

1.3 LITERATURE SURVEY ON PREVIOUS STUDIES ON METAL

CHELATES WITH LIGANDS CONTAINING OXYGEN-

NITROGEN AND OXYGEN-OXYGEN DONORS.

1.4 AIM OF THE PRESENT INVESTIGATION.

1.5 REFERENCES.

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1 INTRODUCTION

Chemistry is an active evolving science that has vital importance to our world

in both realm of nature and the realm of society. Its roots are ancient but at every

beat it is modern science. Therefore, chemistry is a modern science of 21st century1.

1.1 Introduction to Co-ordination chemistry:

Co-ordination chemistry is a branch of Inorganic chemistry which involves the

study of the molecular compounds known to be formed by the union of stoichiometric

ratio and capable of independent existence. These compounds have been

designated as complex compounds or co-ordination compounds. Therefore addition

or molecular compounds which retain their identity even in solution and the properties

of which are different from their constituents are termed as complex salts or co-

ordination compounds2. In other words, a co-ordination compound or complex is

formed when the Lewis base (donor) is attached to a Lewis acid (acceptor) by means

of “lone pair” of electrons3.

In recent days large area of Inorganic Chemistry research is acquired by co-

ordination chemistry due to its interesting and significant properties Co-ordination

chemistry has always been a challenge to researchers. Majority of biologically active

compounds are co-ordination compounds4.

The knowledge about coordination compounds has been developed from

pioneer work of A. Werner5 in 1893. Werner was the first who could able to explain

the nature of bonding in complexes. He proposed that in co-ordination compounds

the central metal exhibits two types of valencies that are primary and secondary. The

primary valency is ionisable and non-directional while secondary valency is non-

ionisable and directional. For this revolutionary work Alfred Werner was awarded a

Noble prize in 1913. Brown6 classified the complexes, Tambe-Blomstrand7 and

Jorgensen8 pointed out the relation between different classes and the structure of

complex compounds.

Werner’s work was elaborated by Lewis9, Kossel10. Sidgwick11, and Fajans12.

Linus Pauling13 and others finally developed the work into ‘Valence Bond Theory”

(VBT) in 1931.

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In the complex the metal ion or metal atom is present at the centre and

has the capacity to accept lone pair of electrons resulting into coordinate bond or

dative bond. The number of bonds formed by donor atoms with central metal species

is termed as “Co-ordination Number” which exhibits the specific characteristic of

central metal ion, related to the positions of metal ions or atoms in periodic table. Co-

ordination chemistry deals with the large number of metallic elements belonging to s-

block, d-block, f-block and higher members of p-block of the periodic table. The

stability of complexes have explained by Sidgwick with the help of EAN rule which is

nothing but the fact that central metal ion or atom acquires the same effective atomic

number of next inert gas. In fact some compounds obey EAN rule while some do not.

In 1931 Pauling gave VBT which is based on the unique and revolutionary

idea regarding the concept of hybridization. According to VBT, the central metal ion

or atom makes available number of empty or vacant orbitals equal to its co-ordination

number. These empty metal orbitals undergo pearticular types of hybridization such

as sp, sp2, sp3, dsp2, dsp3, sp3d. d2sp3 or sp3d2 and sp3d3 with moleculer shapes or

geometries like linear, trigonal, tetrahedral, square planer, trigonal bipyramidal,

square pyramidal, octahedral or square bipyramidal and pentagonal bipyramidal

respectively. The filled ligand orbitals overlap with vacant hybrid metal orbitals with

the formation of co-ordinate covalent bond. This theory explains mainly electronic

structure of central metal ion or atom, geometries of complexes, concept of inner

orbital and outer orbital complexes, magnetic moments and stereochemistry.

However, it does not give proper explanation of maximum pairing, complex spectra

and quantitative interpretation of magnetic properties.

Crystal Field Theory (CFT) developed by Bethe14 and Van Vleck15 is another

advanced approach in the study of complexes. According to CFT, the bond between

metal and ligand is purely electrostatic and it is neither due to sharing of electrons nor

due to interaction of atomic orbitals. The effect of interaction of metal d-orbitals with

the surrounding ligands is the formation of crystal field which removes the

degeneracy of metal d-orbitals resulting into crystal field splitting. The energies of the

sublevels of orbitals depend upon the type of geometry. e.g. in octahedral or oh

complex, five metal d-orbitals get splitted into t2g-triplet with lower energy and eg

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(doublet) with higher energy splitting mode is basically related to the orientation of

metal d-orbitals and direction of the ligand approach in specific geometry. The energy

difference between t2g and eg levels in octahedral complex is the Crystal Field

Stabilization Energy (CSFE) which is denoted as l0Dq or ∆o.

For tetrahedral and square planer complexes it is designated as ∆t and ∆sq

respectively. The magnitude of 10Dq depends mainly upon nature of ligand (e.g.

position in ECS) and charge on the central metal. CFT gives quantitative

interpretation of magnetic and spectral properties of co-ordination compounds.

Van Vleck15 and Mulliken16,17 developed (MOT) i.e. molecular orbital theory

which provides quantitative interpretation for all the properties of coordination

compounds. In MOT the bonding between central metal species and ligand is

considered as ionic, covalent and intermediate. The energy level diagram for a metal

complex18 includes bonding orbitals, non-bonding d-orbitals on metals and

antibonding orbitals formed by overlap of the orbitals of metal ion and orbitals of

ligands with appropriate symmetries. MOT satisfactorily accounts for the spectral and

magnetic properties of metal complexes including those of the π-type, like metal

carbonyls and metal olefins19.

Ligand Field Theory20-22, (LFT) is developed in recent years which is the

modern extension of CFT. LFT correlates the physical properties of co-ordination

compounds with the nature and position of the ligand in ECS which reflect change in

ligand surrounding which can be divided in three categories e.g. thermodynamic,

spectral and magnetic. In the first category the splitting of the d-orbitals under the

influence of ligand field is disscussed23. The second category gives the electronic

transitions taking place between ground and excited levels of co-ordination

compounds 24, 25. The spin and angular moments of electrons in the filled shell give

rise to magnetic properties.

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1.1.1 Chelates:

Rossotti26 has defined the co-ordination complex as a chemical species

formed by two or more species one of which is metal ion and others are ligands.

Ligands are able to form either one bond with central metal (monodentate) or more

than one bond with central metal (polydentate). Interaction of polydentate ligand with

metal ion results into a cyclic structure consisting heteroatoms. The term “Chelate”

was first introduced by Morgan and Drew27 to describe such cyclic structures arising

from the combination of metallic species with polydentate organic or inorganic ligand

species. The heterocyclic rings are termed as ‘chelate rings’ and the phenomenon is

known as ‘Chelation’. The term ‘Chelate’ was taken from the Greek word ‘chela’

meaning crabs claw. The analogy is obvious because donor atoms from ligand may

hold an object (central metal) through more than one point of attachment and form

heterocylic ring. More recent treatment is observed in the book written by Martell and

Calvin29.

Out of the most striking properties of chelates is their unusual stability pointed

out by Feitter29.Therefore they resemble the aromatic rings encountered in organic

chemistry. The stability of chelate depends upon the size and number of atoms

involved in the ring. Generally co-ordination compounds formed by five membered

rings are more stable than unsaturated five membered ring. However, a greater

stability is achieved with the formation of six membered rings. The co-ordination

numbers of metal are generally four and six. The well known example of chelate in

animal kingdom is haemoglobin. i.e. red pigment present in the blood which is Fe-

phorphyrine chelate and in plant kingdom is chlorophill i.e. green pigment needed for

photosynthesis which is Mg-porphyrine chelate. This suggests a need for the study of

metal-chemistry involved in biological systems30 which may be tittled as bio-

inorganic chemistry.

The formation of co-ordinate covalent bond with central metal ion or atom and

donor atom of ligand may proceed with or without replacement of hydrogen atom

from organic functional groups. Majority of chelating agents i.e. ligands involved in

chelate formation belong to organic chemistry. With this point of view co-ordination

chemistry, may be considered as inter-disciplinary branch or bridge between

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Inorganic chemistry and Organic chemistry because it involves the combination of

metal ions or atoms with donor groups of chelating agents.

Following are the type of functional groups observed in chelating agents-

(A) Functional groups which combine with metal ions by replacement of hydrogen –

-COOH (Carboxylic) -OH (Phenolic)

-SO3H (Salphonic) -SH (Thiophenolic)

>C=N–OH (Oxime) >C-N–H (Imine) etc.

(B) Functional groups which combine with metal ions without replacement of

hydrogen –

- OH (Alcoholic) -NH2 (Primary amine)

- SH (Mercapto) -NHR (Secondary amine)

- O – (Ether) -NR2 (Tertiary amine)

> C = S (Thiocarbonyl) - CH = CH – N< (Enamine)

> C = N- R (Alkylimine) - S – (Thioether )

O

NEnamino Ketone etc.

1.1.2 Application of co-ordination compounds:

Co-ordination chemistry has found many more applications in various

branches of science such as-

a) Analytical chemistry31

b) Biology32

c) Catalysis33, 34

d) Pharmacology35

e) Metabolic activities36-38

6) Medicines39, 40

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1.1.3 Importance of co-ordination compounds in biol ogical systems:

Co-ordination compounds possess the ability to influence many of the reactions

upon which number of vital processes of living organisms depend. Excellent theories

are available on some of the naturally occurring co-ordination compounds.41,42

It may be observed that many of the capitalized compounds are biological

catalysts known as enzymes. .Enzymes generally consist of a protein part which

account for the bulk weight of the molecule and a non-protein part i.e. prosthetic

group.

The participation of complex compound in nearly every phase of biological

activity is classified as –

1. Bond formation and cleavage

2. Exchange of functional groups

3. Blocking of functional groups

4. Influence upon stereochemistry

5. Oxidation reduction reactions

6. Storage and transfer

7. Transmission of energy

Metal ions play an important role in many of the bond making and bond

breaking reactions in natural processes. The acceleration of bond cleavage as a

result of co-ordination may be attributed to the polarisation of electrons towards metal

and therefore away from organic molecule. Thus the activation energy necessary is

considerably lowered43.

e.g. Zn forms an essential part of a number of enzymes including carbon

anhydrase, alcohol dehydrogenase, alkaline phosphatase, glutamic dehydrogenase

and lactic dehydrogenase. Zn is also playing an important role in the biological action

of insulin. Nickel, Cobalt and Cadmium also react with insulin polypeptides44,45. A

calcium protein complex known as enterokinase aids in the conversion of

chymotrypsin into trypsin46,47.

In addition to bond forming and rupturing reactions, metal ions participate in

group transfer reaction. eg. Enzyme Transaminase which contains chelating

substance pyridoxal. Transmutation provides link between carbohydrate and protein

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metabolism through the transfer of amino group from amino acid to keto acids. The

requirement of vitamin gave that amino acids initially form schiff‘s bases with

pyridoxal. Haemoglobin and chlorophyll are porphyrin chelates while vit. B12 is corrin

chelate observed in biosystems.

Redox reactions are of fundamental importance in biochemical processes in which

metal ions play an important role in the form of complexes.

1.1.4 Importance of Co-ordination compounds in medi cine or as drugs:

Many drugs become biologically active by forming complexes with important

biological metabolites or enzymes. Hence, number of studies appeared in literature

concerning with drugs.

(I) ANTIMICROBIAL AGENTS-

The activities of certain antimicrobial agents (i.e antibiotics) depend in part

upon their ability to form chelates. e.g.

a) Tetracycline s – It is suggested that chelation is involved in the mechanism

of tetracyclines. Attempts have been made to prepare chelates for the theorapeutic

purposes with Fe3+, Co3+

, Al3+, Sn 2+, Cd2+, Pb2+, Cr3+, Mo5+ and rare earths48, 49.

Tetracycline complexes are also prepared with Be2+, Co3+, Ni3+ 50,51, Ransmeir52

prepared complexes with Ca & Al while Benet & Goyan53 used Cu for complexation.

Oxytetraycline complexes are prepared54 with Co3+, Fe3+, Mn2+, Ni2+, Ca2+, Zn2+, Al3+,

Cr3+, Cu2+ & Mg2+

b) 8- Hydroxyquinoline (oxine ) – This is well known chelating agent which

exhibits antimicrobial, amoebicidal and fungicidal properties55,56. The effect of oxine

upon gram positive bacteria is more than upon gram-negative bacteria, 8-

hydroxyquinoline appears to penetrate cell membranes, as a fat- soluble complex

with metals. The Cu2+ complex easily pass into parasite body, liberate Cu & kill the

invader57.

The antimicrobial properties of penicillin58, Bacitracin59, Cycloserine60,61, Kojic

acid62, Morin59, α-nitroso-β-naphthol, polymyxin62 and α-Picolinic acid59 are evidently

related to their chelating ability as their activity is affected by certain metals.

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(II) Antituberculotic agents

Streptomycin is a good chelating agent. Chelates of streptomycin with Fe3+ 63

have been reported. Mixed complexes of dihydro-streptomycin and Penicillin- G with

Fe3+, Cu2+, Co3+, Ni2+ and Th4+ have been studied64. The activity of streptomycin has

been reported to be inhibited by addition of Cu2+, Co2+, Ni2+ 65, Ca 2+ and Mg2+ 66.

Other antituberculotic agents are p-aminosalicylic acid, thiosemicarbazone

and aspergellic acid67. p-aminosalicylic acid and alcoholic gold salt react to form gold

complex which is useful antitubercular68.

(III) Analgesics in rheumatoid diseases and fever:

The antirheumatic action of orthohydrobenzoic acid (salicylic acid) is due to its

ability to form complex with heavy metals69, while meta and para forms are ten times

less effective than orthoforms.

Gold derivatives used in rheumatoid arthritis are sanocrysine, myochrysine,

solganal auranofin, sodium p-hydroxybenzoate and gold thioglucolanalide (Leuron)70.

(iv) Diuretics –

The effectiveness of organomercurial diuretics is attributed to their ability of

inhibition by complex formation. Recent studies have demonstrated that mercury

remains bound as the organo-mercurial complex R-Hg–X71,72 in kidney. ‘X’ may be a

protein which is exchangable for cysteine or acetyl cysteine complex73.

(V) Antithyroids –

Thiourea and thiouracil are known to react with copper and have marked

antithyroid activity. In the thiouracil series of compounds, there is a positive

relationship between chelating ability and antithyroid activity74.

(VI) Disinfectants and antiseptics –

Copper bis-(marphonylamino) sulphathiazole is useful as bactericide and

antiseptic75. Copper complexes of o-hydroxyazonaphthols and phenanthrols supress

the growth of Microbacterium tuberculosis, both in vitro and vivo76.

Silver nitrate and protein complexes are used as antiseptic and germicide. Silver

picrate is an antiseptic used in gonorrheal and trichomonal infections. Unstable silver

complex of cesin could cure infections and helps to attain higher curative power of

silver complexes of arphenamine77 as silver-bismethyl (2,3-dihydroxy p-phenethyl)

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amino sulphadiazine, Ag-diaminosulphadiazine, Ag-Bis(marphoxylamino) sulpha-

anilamide, Ag-Bis(benzylamine)–sulphadiazine etc. Silver complexes are useful as

bactericide and antiseptic and can be incorporated for external application78.

Organomercurials are used as antiseptics. The inactivation of bacteria by

mercurial may be caused due to their ability of form inactive complexes with

sulphydral enzymes79 without cell injury.

The antibacterial activity of organic compounds of arsenic80 and antimony81 is

brought about by a similar mechanism.

(VII) Antimalerials-

Poludrine one of the antimalerials is reported to act through the formation of

chelate with copper82. Quinoline and p-toluence sulphonamide have been used as

drugs for diseases like maleria,tuberculosis etc.Tewari and Mishra83 prepared metal

chelates of Fe(III ), Co(II ), Ni(II ), Cu(II ) and Zn(II ) with 5-iodo-7-chloro-8-hydroxy-

quinolino-4-(p-tolyl)-sulphonamide and found that the metal chelates were more

active than ligands against several types of bacteria.

(VIII) Vasodepressar and Bronchodilator 84-95-

Such as catechol, amines like adrenaline, nor-adrenaline, dopamine and

isopranaline.

(IX) Anticancer drug-

Like folic acid antagonists, thiogunine adenine etc.96-109 acts as anticancer drug.

(X) Complexes as antidotes or antimetal poisoning d rugs.

Some of the metals are extremely toxic. The treatment of metallic toxicity till a

few years back was considered to be quite difficult due to lack of specific antidotes or

antitoxic species. The development of antagonists to the biological actions is

important in modern pharmacology. The antagonists are valuable drugs. Heavy

metals have toxic effects as they combine with reactive110 groups, essential for

normal cell functions and thereby they block the reactive sites. A number of chelating

agents are developed which show remarkable degree of specificity and hence used

in various intoxification.

Dimercapral, BAL (2,3 dimercapto propanol) form a stable, non-toxic chelate

with arsenic and lead-atoms in Lewisite . Dimercaprol has been used successfully in

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the treatment of poisoning or toxic reactions of mercurials and gold salts111,112,

trivalent antimony113, trivaleut arsenic114, chromium115 and copper116.

Anorther reagent EDTA (Ethylenediaminetetraacetic acid) forms a chelate with

calcium ions in blood and has been used in the treatment of hypercalcimia 117,118 for

dissolving calcified corneal opacities119.

Pericillamine, a degradation product of penicillin is used as a chelating agent

in the case of Cu, Hg, Zn and Pb Poisoning120,121. It is an effective drug for Wilson’s

disease which is caused by deposition of copper in various tissues, in toxic

amounts122-124.

Desferrioxamine is a chelating agent which is used in the treatment of excess

iron storage diseases and hence acute iron poisoning. Desferrioxamine has been

found to have a remarkable affinity for ferric iron.

From the above paragraphs it would be clear that there is a continuous search

for newer and newer metal complexes of novel ligands which would possess

applications in variety of fields.

In 1965 Rosenberg125-127 discovered the anticaner activity of cis-platin which is

platinum complex. Since then platinum complexes of different ligands have been

investigated and found to possess antitumour activity and are used in cancer

chemotherapy and are known as anticancer agents128,129.

The antileukemia properties of many130,131 organoplatinum complexes have

been reported .

Celave et al.132,133 Studied a series of Co(II). Cr(III) Complexes from which only

[Co(NH3)4Cl2] Cl and [Co(NH3)3CO3] NO3 showed anticancer activity.

Therefore a number of organic compounds possessing physiological activity

and ability to act as ligands are being synthesized of which some of the examples are

carboxylic acids134, aldehydes, phenols136, ketones137, nitrocompounds138, amino

acids139, alkaloids140, thiozines141,142,3 β-diketones143, schiff’s bases19,4,2 and

enaminoketones144-147.

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1.2 Ligands containing Oxygen and Nitrogen as dono r atoms and

their metal complexes

1.2.1 Schiff’s bases - Schiff’s bases are condensation products of amines with active

carbonyl compounds. They are also known as imines148, anils and azomethines.

They contain azomethine (>C=N-) group and hence act as effective ligands. It was

first synthesized by Schiff149.

R'

RO

HN

HR"

R'

RN

H2OR" +

Active Carbonyls Pri-amine Schiff's base

The Schiff’s bases are more effective when they bear supporting and

stabillizing group like- OH in the vicinity of >C=N group. Therefore the chemistry of

Schiff base metal complexes attracted many researchers and has been developed

rapidly in recent years150. Hydrazones, carbazones semicarbazones,

thiosemicarbazones, thiocarbazones, oximes etc. are some of the important classes

of Schiff bases that have been studied extensively151.

Mane153 has synthesized complexes of Cu(II ), Ni(II), Co(II ), Fe(III ) and Mn (II ) metal

ions with Schiff bases derived from dehydroacid (DHA) and primary aromatic amine

like m-chloroaniline, m-aminophenol, m-anisidine, m-toluidine, m-bromoaniline, 3,4

dichloroaniline m-amino benzoic acid and o-phenitidine and characterized.

Pachling152 reported the synthesis and characterisation of Fe(III ), Cr(III ), Cd(II ),

Hg(II ) & Pb(II ) complexes of schiff base derived from DHA and semicarbazide like

amines. Pandhare19 reported the synthesis and characterization of complexes of

schiff’s bases derived from o-aminophenol and substituted aldehydes.

Maurya et al.154 reported the synthesis, magnetic and spectral studies of some

novel binuclear-dioxo molybdenum VI chelates involving Schiff bases derived from

sulpha drugs and 4-benzoyl-3-methyl-1-phenyl-2-pyrazolin-5-one.

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1.2.2 ββββ-Diketones -

β-Diketones comprises a class of compounds characterized by the presence

of two –OXO- groups –(-CO-CH2-CO-). β-diketones possess good chelating ability

and they show enhanced biological activities. Khot2 reported synthesis and

characterization of complexes of transition metals with β-diketones. Mathews

Cheriyan155 synthesized and characterized the complexes of Co(II ), Ni(II ), Cu(II ) and

Zn(II ) with 2-(2-carboxyphenylazo)-1,3-diketones.

Ismail Patel156 synthesized Mn(II ) complexes with Schiff bases derived from

heterocyclic β-diketones and some diamines.

1.2.3 Chalcones-

Chalcones are the condensation product of acetophenone with aromatic

aldehydes in the presence of strong base. Chelcones and their metal complexes

show significant biological activities. Chalcones are nothing but α, β-unsaturated

ketones. Patange3 reported the synthesis and characterization of complexes of

Mn(II ), Fe(III ), Co(II ), Ni(II) and Cu(II ) metal ions with chalcones derived from

dehydroacetic acid (DHA) with hetetrocyclic aldehydes.

General structure of ligand used in above work is-

O

Ar

OH3C

OH O

α

β

1.2.4 Enamines or Enaminoketones-

The term “enamine’ was first introduced in 1927 to emphasis the structural

similarity between the α,β-unsaturated amine system and the α,β-unsaturated

alcohol moiety present in enols157. Isolated reports concerning the reactions of

enamines date back to the early nineteen hundreds. Indeed in 1916 Robinson

correctly interpreted. The course of the reaction between an alkyl halide and ethyl β-

amino-crotonate158, 159. However, it was not until 1954, when Stork and his associates

described alkylation and acylation reactions, and demonstrated the ease of

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preparation of a number of enamines160, that general interest was arose. Since then

a considerable amount of work has been reported on a variety of enamines,

expanding the scope of the original observations.

Preparation and some properties-

The most common procedure for enamine formation, which was first used by

Herr and Heyl in 1952, then exploited by Stork160 et. al. involved heating under reflux

an equimolar mixture of carbonyl compound and the amine in a solvent such as

anhydrous benzene, toluene or xylene with azeotropic removal of water.

Preparation from aldehydes and ketones:

The most versatile and most often used method of formation of enamine

involes the condensation between aldehyde or ketone and a secondary amine.

a) C C

O

H

HN CC

N H2O

The mechanism of the reaction is usually expressed as follows.

C C

O

H

HN

R'

R"

H

OH

NR'R"

(I)

H

NR'R"

(II)

NR'R"

(III)

H

O+H2

NR'R"

(III)

OR

In the acid catalyzed reaction presumably the N-hemiacetal (I) is protonated to

(III ). The actual rate of enamine formation depends upon the several factors in a

complex way such as-

i) The basicity of amine.

ii) The degree of steric hindrance in either the amine or ketone, which affects

the rate of formation of (I)

iii) The rate of loss of the hydroxyl group from (I) or (III ) and

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iv) The rate of loss of a proton from (II)

The enamine once formed may be isolated by distillation.

The most commonly used compounds have been the cyclic amines.

N Hi.e. a) Pyrrolidine

b) Piperidine

c) Morpholine

NH

NHO

If a molecule contains both aldehyde and ketonic functions like 2-oxocyclohexane-

carbaldehyde reaction with secondary amine occurs as follows-

O

CHO

2-oxocyclohexanecarbaldehyde

NHR'R"

O

CH-NR'R"

One of the properties of enamine is protonation. And basically the structure of

enamine system may be regarded as a resonance hybrid to which following canonical

forms (a) and (b) are important contributors157.

CCH

N CCH

N

Hence electrophilic reagents include protons, may attach the system at either the

nitrogen atom to give ammonium salt –

CC

NR

Or more importantly, at that carbon atom β to the nitrogen to yield an iminium salt-

αβ

R

CC

N

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Joshi et. al.161 reported the reactions of thiosemicarbazide with 3-formylchromone

and synthesized some pyrazole and enamine containing organosphorous162 compounds

in view of activities associated with heterocyclic compounds163.

3-Formylchromones when treated with thiosemicarbazide in alcoholic KOH gave

compound (I) which when treated with sodium metal in dry THF followed by treatment

with O,O-diethylphosphorochloroido thiolate yielded compounds (II) and (III) 163.

Formylchromones when heated with piperidine in ethanol yielded compound (III ) termed

as enaminoketone.

O

O

CHO

R1

R2

R3

Thiosemicarbazide/ Alc. KOH

Heat 3 hrs

O

R1

R2

R3

N

NH

(I)

Na/ THF

POC2H5

S

OC2H5

OH

O

R1

R2

R3

N

(III)

Enaminoketones

R1

R2

R3

N NH

(II)

OH

O

Piperidine/Ethanol

P OC2H5

S

OC2H5

Cl

O

Among the different functionalized chromones 3-formylchromones occupy a

unique position because they can be transformed into various heterocycles163-165.

The reactivity of 3-formylchromone towards several nucleophiles such as hydrazine,

phenyl hydrazine and particularly two functional nucleophiles, e.g amidines,

derivatives of guanindine and isothiourea was investigated166.

3-Formylchromone when treated with piperidine167 under reflux gives 1-(2-

hydroxy-phenyl)-3-piperidin-1-yl-propenone, which is enamine function.

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O

O

CHO

R1

R2

R3

OH

O

R1

R2

R3

NEthanol

RefluxN

H

Iminoketones or ketoenamines are versatile synthones which can be

converted to variety of heterocyclic compounds168. The compound 1-(2-hydroxy-

phenyl)-3-piperidin-1-yl-propenones were utilized for synthesis of bioactive

organophosphorous compounds163.

Dalvi et.al.169 synthesized different 1-(2-hydroxy-phenyl)-3-piperidin-1-yl-

propenones by ultrasonic activation from differently substituted 3-formylchromones

and piperidine. For the method of ultrasonic irradiation the time required for

completion of the reaction is less and yields are better than conventional method.

Piperidine reacts with 3-formylchromones by attacking the electron deficient centre of

C2 carbon and the probable mechanism is as follows-

O

O

CHO

R1

R2

R3

OH

O

R1

R2

R3

N

N

H

O

O-

CHO

R1

R2

R3

N+HO

O

R1

R2

R3

N

O

H

N

H

O-

O

R1

R2

R3

N

N+H

O

H

The required 3-formylchromones are synthesized by Vilsmeier-Haack reaction

on variously substituted 2-hydroxyacetophenones derived from phenols by Bechman

rearrangement.

Karale170 described the syntheses of a series of organic compounds of varied

classes such as chromones, aminopyrimidines, thiopyrimidines, pyrazoles,

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benzothiazepines, dihydrobezothiazepines, fused amino and thiopyrimidines,

coumarins etc.

While referring the literature servey of the above classes of compounds it was

found that they are associated with various physiological and biological properties

and thus find importance in medicine.

A number of scientists in the past have tried to find out some relationship

between chemical structure and physiological or biological properties. It is now well

established fact that the activity of a compound depends upon three factors. The first

and perhaps most important is the heterocyclic moiety present in the particular

compound. The second factor is the nature of the substituents and the third factor is

the position of the substituents in these compounds.

4-Oxo-4H-[1]benzopyran-3-carboxaldehyde is a versatile synthone171 and can

be converted into large no. of heterocyclic compounds such as pyrimidines,

pyrazoles, oxazoles upon condensation with different nucleophiles. These 3-

formylchromones give important intermediates, which can be used in the synthesis of

some important heterocyclic compounds e.g. 4-heteryl coumarins172.

The effective and facile method for the synthesis of 3-formylchromones was

developed by Nohara et. al.173 They have synthesized a number of 3-

formylchromones by formylating various 2-hydroxy acetophenones by the application

of Vilsmeier-Haack reaction. The most suitable formylating reagent was a complex of

dimethylformamide and phosphorousoxychloride. The reaction can be represented

as follows.

R1

R2

R3

OH

O

DMF/POCl3

R1

R2

R3

O

CHO

OR4 R4

4-Oxo-4H-[1]benzopyran-3-carboxaldehydes when condensed with primary

aromatic amines gives 3-(aryliminomethyl)-chromones i.e. schiffs bases or anils. The

reaction between equimolar quantities of 3-formylchromones and primary aromatic

amine invariably lead to a mixture of the anil (a) and 1,4-adduct (b)173.

20

R3

O

CHO

O

NH2

R5

R6

R7

R1

R2

R4

R3

O

OH

N

R5

R6

R7

R1

R2

R4

R3

O

O

HN

R5

R6

R7

R1

R2

R4

NH

R5

R6

R7

(a)

(b)

Pyrazoles are associated with bactericidal174, antiinflamatory175 and

hepatoprotective176 activities. Chalcones are associated with bacteriostatic177,

tuberculostatic178and insecticidal179 activities.

Chandrakanta Ghosh180 gave that 3-acetyl-4-oxo-4H-[1]benzopyran gives(1a)

gives enaminoketons(2) with piperidine.

R1

R2

R3

OH

O

R1

R2

R3

O

COMe

O

R

1a

N

2

Of the 3-acetyl-4-oxo-4H-[1]benzopyran (trivial name: 3-acylchromenone) the

reactions of 3-formylchromones have been extensively studied171.

Zagorevskii181 et al. studied the mechanism of the opening of the pyron ring of

chromone during the action of amines.

Ghosh182 et al. reported the base catalyzed reaction of EtOH with α-Cyno-

acrylic esters (I-R=OH, R1=CN, R2=H, Me) which gives the pyranobenzopyrans (II -

R3=CO2Et, R4=OEt). Similar reaction of EtOH, MeCOCH2COMe, EtO2CCH2CO2Et,

MeCOCH2CO2Et with azalactones (I; R, R1= N:CPhO) produces the fused pyrans [II-

R3=NHCOPh, R4=OEt,CH(COMe)2CH(CO2Et)2CH(COMe)CO2Et]. Piperidine

converts chromone derivatives (I; R=CO2Et, COMe, CN; R1=OEt) into the

21

transenaminoketone (E)-(III ). The pyranobenzopyrans [II ; R3=NHCOPh; R4=CH

(COMe)2, CH(CO2Et)2, CH(COMe)CO2Et] react with pyridine-acetic anhydride to form

the acetates (IV ; R5, R6=me, OEt) corresponding to open the chain tautomers of the

former.

R2

O

CH:CRCOR

O

R

IR2

O R4

II OR3

O

R2

OH

O

NR2

OAc

O

CH:C(COR5)COR6

NHCOPhIII IV

Ghosh et al.183 reported the study of defunctionalization of acids and various

substituted aldehydes to the respective chromones (II) via o-hydroxy acrylphenones

(III). A mixture of substituted chromones (I) and piperidine in ethanol was refluxed to

yield enaminoketones (III), while heated with conc. H2SO4 in ethanol to give (II)

Me

OH

O

Me

O

CO2H

O

N

I IIIMe

O

OII

Zagorevskii184 et al. reported the structure of products from the opening of the

pyran ring of 4-pyrones by amines.

Yong-Ming-Wu185 reported synthesis of 2-bromodifluoromethyl quinoline

derivatives and difluoromethylene thioether by cyclization of β-bromo difluoromethyl

β-enaminoketones.

22

N OH

Ph

1

R

BrF2CN OF2Br

2

PPA

120oC

Ph

R-XH/ Base R-XH/ Base

OH

NO

H

Ph

4

MeO

R-X

FF

N

Ph

HOOC

3

XR

FF

R

23

1.3 Literature survey on previous studies on metal chelates with

ligands containing Oxygen, Nitrogen and Oxygen-Oxyg en

donors-

The literature survey gives that the scope of co-ordination chemistry is vast.

The new horizons of this chemistry extends its tendencies to various interdisciplinary

fields. The development of numerous newer organic chelating agents that can

coordinate with metal ions has opened up a broad scope to a research scientist in

synthetic field. In the last few decades a lot of work has been done on metal

complexes in solution as well as in solid state.

Transition metal ions in particular form stable complexes having variety of

applications in different fields. Therefore the synthetic study of transition metal

chelates has become the remarkable flowering of inorganic chemistry which has

enriched the chemical science to a high degree.

1.3.1 Brief account of Manganese [ II] Complexes-

Manganese is the twelth most abundant element by weight in the earth’s crust.

It is biologically important in photosynthesis; it shows 2+ as most stable state in

complexes.

Mn(II ) with d5 configuration corresponding to half filled ‘d’ shell is more stable

than other divalent transition metal ions. Most of the complexes are six co-ordinated

and have high spin arrangement of five unpaired electrons186. Some complexes have

square plane and tetrahedral geometries with Coordination Number 4.

Chondhekar187 reported Mn (II) chelates with Schiff bases derived from 5-

hydroxy acetophenone and aromatic amines. The complexes are reported, possess

dimetric tetrahedral geometry on the basis of their spectral and magnetic

susceptibility measurements. Magnetic moments were found to be in the range 4.86-

5.85 B. M. and complexes show M: L ratio 1:1.

Kuntebommana halli et al.188 reported Mn (II) complexes of vanillin

thiosemicabazone(VTSC).

Rao et al.189 reported Mn(II) complexes of Schiff bases derived from 1-tyrosine

hydrazide and o-hydroxy acetophenone.

24

Singh et al.190 reported Mn(II) complexes of Schiff bases derived from

salicylaldehyde and 2-aminobenzophenone-2-thionylhydrazone191.

S

O

HN

N C

NHC

OM

Syamal and Mourya191 have studied Mn(II), Ni(II), Cu(II) and Zn(II)

dioxouranium(VI) and dioxomolybdenum(VI) complexes of tridentate dibasic ONO

donor Schiff base derived from 2-benzothiazole.

Shukla P R192 reported complexes of Mn(II), Fe(II), Co(II) and Ni(II) with some

tri, tetra and hexadentate Schiff bases.

Jojo Joseph et al.193 reported spectral and lattice parameters of transition

metal complexes of polydentate Schiff bases derived from 3-formyl-4-hydroxy

coumarin and 4-amino phenol/2 amino benzoic acid with Mn(II), Co(II), Ni(II) and

Cu(II).

Patel et al.156 reported Mn(II) complexes with Schiff bases derived from β-

diketones and some amines.

Mandlik et al.194 reported synthesis and characterization of Mn(II), Cr (III), Fe

(III), VO(IV), Zr(IV) and VO2(VI) Schiff base complexes.

Aswale et al.195 synthesized Mn(III),Fe(III), Ti(III) etc polychelates derived from

bis-bidentate salicyaldimine.

Hankare et al.196 reported synthesis and characterization of complexes of

Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with Schiff bases derived from 5-

(2’-thiazolylazo) salicylaldehyde and p-methoxy aniline.

Mitu et al.197 reported synthesis and characterization of Mn(II), Co(II), Ni(II),

Cu(II), Zn(II), Cd(II) complexes of Isonicotinoylhydrazone-1-methyl-2-aldehyde-

pyrrole.

25

Sivakolunthu et al.198 reported synthesis and characterization of Mn(II), Co(II),

Ni(II), Cu(II) and Zn(II) complexes with 8-quinolinyloxyacetic acid.

Khan199 reported complexes of Mn(II), Co(II), Ni(II), Cu(II), Fe(III), Cr(III), Zn

(III) etc with 1,1-(2,6-pyrimidyl-bis-benzothiazole)-2-thione.

Maurya et al.200 reported the synthesis ans characterization of Mn(I)

complexes of biologically active oxygen donor 2 or 3 pyrazoline-5-one derivatives.

NC

NC

OH2

O

NH2

N

Mn

O

C

C NN

C

CH3

CH3

Shakir Mohammad201,202 reported synthesis and physicochemical studies of

complexes with Mn (II), Co(II), Ni(II), Cu(II) and Zn(II) with macrocyclic ligands

derived from 2, 6-diacetylpyridine dihydrazone.

Verkey and Jacob 203 reported synthesis and characterization of zeolite

encapsulated Mn (III) salen complexes.

O

R'

R N

MnO

RN

Cl

R'

Mitu et al.204 synthesized and characterized the complexes of Mn(II), Co(II),

Ni(II) and Cu(II) with Aroylhydrazone ligand.

Hankare et al.205 reported synthesis and characterization of Mn(II), Co(II),

Ni(II) and Zn(II) azo coumarin complexes as follows:

S

N NN

OH

CH

N

OCH3

i) Structure of ligand

26

S

N

NN

O

CH

N

H3CO

S

N

N

N

O

HC N

OCH3

M

M

Cl

Cl

ii) Structure of Complex

M= Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)

Nakamura et al.206 reported the method for stabilizing β-diketone metal

complexes and their compositions for metallographic CVD by selecting metals like

Cu, Fe, Mn, Zn, Al, etc. using R-1COCH2COR2 (R, R2= alkyl groups) in organic

solvent.

Structure of the square planer Cu-L2 complex.

O

O

N

MO

OH

O

N

HO

O

O

Chondhekar et al.207 reported the synthesis of transition metal complexes of

Mn(II), Fe(II) etc with 2-hydroxy / 5’-chlorophenyl acetophenones and p-nitromethyl

benzoic acid and benzaldehyde.

Irudayasamy208 reported the synthesis of complexes of Mn, Fe with 2’-

hydroxychalcone and characterized on the basis of elemental analysis, conductance,

magnetic, electronic and IR studies and found that the complexes are monomeric low

spin and square planer.

27

Peng and yanging et al.209 reported ionic-liquid grafted mn(II) Schiff base complex

prepared with imidazoline and employed as an efficient and recyclable catalyst for

the epoxin.

Swamy210 reported formation constants of metal chelates of

2’hydroxychalcone and 2’hydroxy-5’ methyl chalcone with bivalent metals like Mn(II),

Ni(II), Zn(II), Cd(II) etc

Booth et al. 211 reported reactions between methyl, acetyl and

phenylpentacarbonyl Manganese and acytylenes. The reactions undergo Cis

additions, The PMR and IR Spectra are described.

Nesmeyanov et al.212 reported anisotropic rearrangement of tertiary α-

acetylene alcohols by cyclopentadienyl tricarbonyl manganese and concluded that

the stabilisation of the carbonium ion by C5H4Mn(CO3)3 is probably due to Mn or M-

C5H4 ring electrons.

Abrahams et al.213 reported in situ synthesis of trisubstituted methanol ligands

and their potential as one pot generators of cubane like metal complexes. When

excess Na Sulphite was used, the monoanionic complexes M3Na{(C5H4N)2SO3C(O)-

4} M= Mn, Co, Zn with an M3NaO4 cubane core are formed directly from 2,2’ dipyridyl

ketones.

Nair et al.214 reported synthesis of crosslinked divinylbenzene Me-

methacrylate co-polymer supported β-diketone linked complexes of Mn(II), Fe(III),

Co(II), Ni(II) and Cu(II) and studied the influence of degree of cross-linking of the

polymer support, structural environment of ligand and nature of metals on the rate of

reactions.

Pike et al.215 reported synthesis of dioxyanthraquinone-bridged bimetallic β-

diketonate complexes of Mn(III), Fe(III), Al(III), Cr(III), V(III) and characterized for Uv-

Vis, IR, NMR and fluorescence studies.

Taft et al.216 reported the preparation and characterization of Mn and Fe

alkoxide cubes and found that in [Mn4(OEt)4(EtOH)2(DPM)4] the 4 metal ions and

bridging alkoxides ligands are located at alternating vertices of a cube with either

alcoholic or alkoxide and β-diketonate or benzoate ligands on the exterior of the core.

28

Patel et al.217 reported physiochemical studies of metal β-diketonates. V.

spectral and magnetic properties of Mn(III), Fe(III), Co (III), Al(III) and Cr(III)

complexes of 1-(2-thienyl)-1,3-butanedione and 4, 4, 4-trifluoro-1-(2-thienyl)-1,3-

butanedione.

Patel et al.218 reported physiochemical studies of Mn(II), Fe(III), Co(II), Ni(II),

Cu(II), Zn(II) and Pd(II) complexes of 1-(3-pyridyl)-1,3-butanedione and 4, 4, 4-

trifluoro-1-(3-pyridyl -1,3-butanedione with respect to magnetic and spectral

properties at 83-300K.

Batyr et al.219 prepared the adducts of heterocyclic amines with bis-β-

diketonates of 3d elements i.e. Mn, Fe, Cu, Ni, Co, Zn etc. and their thermal stability

are studied. Ligands are 2,2’-bipyrine, 1,10-phenanthroline and HФ=acetylacetone

etc.

1.3.2 Brief Account of Iron (III) Complexes-

Iron is the fourth most abundant element in the earth’s crust. It is biologically

the most important transition metal in plants and animals functioning as electron

carrier, oxygen carrier and oxygen storage and forms several unusual complexes186.

Iron (III) ion with its d5 configuration has 3+ oxidation state and forms

octahedral complexes with various ligands in general. The tetrahedral and square

planer complexes of Fe (III) are less reported as compared to its octahedral

complexes. The affinity of Fe (III) for amine ligands is very less. No simple amine

complexes exist in aqueous solution as addition of aqueous ammonia to Fe (III) ions

leads to precipitate it as hydroxide4.

Iron (III) has affinity towards ligands which co-ordinate via oxygen. Octahedral

complexes of Fe (III) like [Fe(CN)6]3- are low spin with one unpaired electron having a

magnetic moment of 1.9 B. M. while the complexes [Fe(H2O)6)+3[FeF6]

-3 etc. are high

spin with five unpaired electrons having a magnetic moment of 5.9 B. M.

The affinity of Fe (III) towards oxygen donor is greater than nitrogen donor220.

It has been observed that urea co-ordinates with Fe (III) via oxygen forming stable

complexes. The unidentate ligands with nitrogen donor do not form stable complexes

in aqueous solution. The complexes of the type [Fe(NH3)6]+3 are formed with gaseous

ammonia but they are decomposed immediately, by water at room temperature with

29

release of ammonia4. Ligands such as bipyridil, 1,10-phenanthroline have chelating

nitrogen donor atoms and form stable complexes with Fe(III). The substitution of

metal ion is difficult in such low spin complexes yielded by strong field ligands. A

large number of stable chelates of Fe (III) with many bidentate, tridentate,

tetradentate and polydentate Schiff base ligands are reported 221-223.

Some dimeric complexes such as [Fe(SAL)2en]2 are reported to have

magnetic moment about 1.9 B. M. at 298oK. These complexes are believed to have a

linear Fe-O-Fe system through which magnetic interaction seem to occur224.

Debey et al.226 studied the Fe (III) complexes of Schiff bases derived from

salicylaldehyde and some amines for their composition and abilities.

Manganese (II) and Iron (III) complexes of 2-hydroxy,2-carboxy-phenyl-azo-β-

diketonses are reported to be dimeric225.

Costamagna227 systematically surveyed the literature on Cu(II), Ni(II), Fe(III)

chelates of 2-hydroxy-1-naphthaldehyde and salicylaldehyde.

Abdula et al.228 synthesized and analyzed Mn (II) and Fe (III) complexes of

Schiff bases derived from salicylaldehyde 2-hydroxy acetophenone and ethylene

diamine and found to posses 1:1 (A)and 1:2 (B) metal to ligand ratio respectively.

O

MNR1

O

N R1

Cl

Cl

(A)

R=-H, -CH3M=Fe (III), Mn(II) (B)

OM

N

C

N

C

O

N

R

O

N

R

O

R

R

Vankat Reddy228 has synthesized and characterized the Fe (III) and

Mn(II) complexes of schiff bases derived from 2-hydroxy acetophenone, 2-hydroxy-4-

methyl acetophenone, salicyaldehyde, 3,5 dichloro salicyaldehyde, benzoxazole

hydrazide and benzimidazole and found to possess octahedral geometry.

Mehta et al.229 reported some six co-ordinated Iron (III) schiff base complexes.

30

Palaniandvar et al.230 have reported Fe(III) complex of tridentate ligand

derived from pyridine-2,6-dicarboxylic acid and catechol with structure-C.

O

Fe

O

X

X

N

SOl(C)

X= O or N

Kenaway et al.231 prepared Fe (III) chelates with 4-(-2-hydroxy)-1-

(2,4dihydroxy

benzaldehyde)-3-thiosemicarbazone.

Patange et. al.3 reported synthesis and characterization of solid complexes of

Mn(II), Fe(III), Co(II), Ni(II) & Cu(II) metal ions with chalcones derived from

dehydroacetic acid aromatic and heterocyclic aldehydes.

Mane et. al.4 reported synthesis and characterization of Mn(II), Fe(III), Co(II),

Ni(II) and Cu(II) complexes with ligands derived from dehydroacetic acid and primary

aromatic amines.

Surya Rao et al.232 synthesized Mn(II), Fe(III), Co(II), Ni(II), Zn(II) chelates of

physiologically active schiff bases derived dehydroacetic acid and thiosemicarbazide,

salicylhydrazide and benzoyl hydrazides. The insecticidal activities of some of the

chelates were good.

O

OM

N

O

H3C

CH3

X

N

M=Zn(II), Fe(III), Co(II), Ni(II), Cu(II) and Mn(II)

X= O or S.

Salunke233 reported the synthesis and characterization of Fe(III), Co(II), Ni(II)

Cu(II) and Mn(II) complexes of azo schiff bases derived from dehydroacetic acid and

p-toluidine, p-anisidine, p-bromoanline, o-toluidine, o-anisidine and β-

naphthylamines. The complexes were characterized by UV, IR, NMR conductance,

XRD and antimicrobial analysis and proposed octahedral structure with dimetric

nature as follows-

31

O

OM

N

N

NM

O CH3

O N

O

ArAr

H3C

Ar

CH3

O

N

N

Ar

Cl Cl

Cl

Radhakrishan et al.234 reported complexes of 1,2 dihydro-1,5-dimethyl 1-2-

phenyl-4-formyl (Benzhydrazide)-3H-pyrazol-3-one with structure-

NN

O

Fe

NHCH3C

H3C

Ph

N CH

O

HN

C

Ph

O

NH

Ph

O

NN

CH3

CH3

Ph

XX

X

X= SCN, Cl or Br.

Shetti et al.235 reported synthesis and characterization of schiff bases derived

from 2,6-diformyl, p-cresol and anilines and obtained binuclear complexes with Fe

(III) as-

Fe

O

Fe

O N

N

N

N

Cl

Cl

Cl

Cl

Dubey et al.236 reported the synthesis, reactions and physicochemical

characterization of Iron (III) complexes containing substituted benzoxazole and

various schiff bases moieties.

Dash237 reported interaction of N, N’ ethylene bis (salicylamide) with Fe (III): A

magneto structural electrochemical and mechanistic investigation.

32

Structure of ligand-

OH

O

HN

HN O

HO

Dash and Rath 238 reported phenol amide chelates of Fe (III) i.e. interaction of

1,5-bis-(2-hydroxybenzamido)-3-azo pentane in aqueous methanol medium.

Structure of the complexe= HLFe(OH)23+.

OH

FeNHO

O

NH

O

OH2

Sureshan et al.239 reported epoxidation of olefins by using Mn (III) and Fe

(III) amide complexes with structure-

O

MO

O

O

NH (CH2)n

NH

HN (CH2)n

nH2OCl

Syamal et al.240 reported synthesis of polystyrene supported chelating resin

containing Schiff’s base derived from salicyladshyde and triethylene tetramine and its

Fe (III), Cu (II), Ni (II), Co(II), Mo (II), Zn (II), Cd (II) and Zr (IV) complexes.

Ajaily et al.241 reported the synthesis and characterization of Fe (III), benzoin

complex with structure having 1:1 M-L ratio.

33

O

Fe

OOH

OH

OH2

OH2

Mitu et al.242 reported synthesis and characterization of Cu (II), Ni (II), Co(II),

Mn (II), Zn (II) and Cd (II) complexes of isonicotinoylhydrazone-1-methyl-2-aldehyde

pyrrole.

Heerdt et al.243 reported the study of single-ion and molecular contributions to

the zero splitting in an Fe (III)-oxodimer by single crystal w-band EPR.

Clegg244 reported the study of dinuclear bis-β-diketonato ligand derivatives of

Fe (III) and Cu (II) and use of the latter as components for assembly of extended

metallo supramolcular structures.

Zutin245 reported the synthesis, electrochemical behavior and X-ray crystal and

molecular structures of [Fe (diene) (CO)2 PPh3] diene=chalcone or Sorbic acid.

Constable246 reported control of Fe (II) spin states in 2,2’,:6’.2”-terpyridine

complexes through ligand substitution.

Singh and Kamaluddin247 reported epoxidation of some α, β-unsaturated

carbonyl systems with tert-butyl hydro-peroxide in the presence of Fe (III) Schiff base

complexe (Fe-salen) 20, as catalyst. Presence of electron withdrawing groups in

Phenyl ring of chalcone and high dielectric constant medium favored the yield of

epoxide.

Galkina248 reported reactions of hydrophosphoryl compounds with iron

carbonyl π−complexes of α-enones.

Hemalatha249 reported the synthesis of Fe (III) complexes with two new

bichalcones i.e. 2’, 4’-dihydroxy-5’-(2-hydroxy) cinnamoyl-2-hydroxychalcone and

2’.4’ dihydroxy-5’-(4-hydroxy-3-methoxy) cinnamoyl-4-hydroxy-3-methoxy chalcone

and characterized by elemental analysis, IR, magnetic and conductance

measurements.

34

Gupta250 reported epoxidation of chalcone with tertiary butyl droperoxide in

presence of Fe(III) Schiff base complex i.e. N,N’-ethylenebis(salicylideniminato) Fe

(II) -µ-oxio-N,N’-ethylenebis (Salicyclideniminato) Fe (III) as a catalyst.

Narawade251 reported stability constants of Fe (III) chelates with some

substituted chalcones like 2’-hydroxy-4-methoxy -5’-methylchalcone.

Daniel et al.252 reported regio- and stereoselective addition of carbon

disulphide Fe-complexes to α, β unsaturated carbonyl in the presence of strong

acids.

Nesmeyanov et al.253 reported preparation and molecular structure of chelates

π-allyl-σ carbamoyliron tricarbonyl complexes.

Syamasunder et al.254 reported spectrometric investigation of iron -2’4’-

dihydroxychalcone complex and predicted that chalcones to be used as analytical

reagents.

Misra et al.255 reported the studies on chalcone complexes of Fe (III) with

HL=RCOCH:CH ph and R=8-hydroxy-5-quinolinyl.

Yu, Zhi-gang et al. 256 reported the synthesis and characterization of diphenyl

benzoylpyrazolone and its metallic complexes with Fe (III). HL synthesized is 1-(p-

chloro –phenyl)-3-phenyl-4-benzoyl-pyrazolone-5.

Prasad et al.257 reported synthesis and spectral characterization of Fe (III)

complexes of dioxadiaza macrocycles derived from α-diketones and 1,8 diamino-3,6-

dioxaoctane.

Nowicki et al.258 reported synthesis, spectroscopic and magnetic properties of

Fe (III) complexes with N’N’ ethylene bis (Salicylaldimide) and β-diketones.

35

1.3.3 Brief Account of Cobalt (II) Complexes-

Cobalt is another important element from first transition series of

d-block of the periodic table. Cobalt belongs to VIII group with atomic number

27. Obviously cobalt has low abundance of only 23 ppm by weight in earth’s

crust due to odd atomic number with d7 configuration. Out of the common 2+

and 3+ oxidation states, 2+ state is more stable than 3+. However 3+ state is

stable considerably and is important in complexes. Co (II) ion forms tetrahedral

or octahedral complexes. Less commonly it forms square planer complexes

with bidentate and tetradentate ligands. Formation of both octahedral and

tetrahedral complexes with the same cobalt salt and ligand is common due to

small difference between the stabilities of these geometries. Sometimes these

two geometries are found to be in equilibrium as reported in compounds of

[CoX2(Py)2] type259. Square planer complexes are formed by tetradentate

ligand such as bis (salicylaldehyde ethylene diaminato) ion and porphyrins.

The Co (II) chelates derived from Schiff bases of bromosalicylaldehyde

and sulphamethoxy pyridazine, sulphamethazole, sulphafurazol have been

reported as six co-ordinated260.

Chondehekar187 reported Co (II) complexes of bidentate Schiff bases

derived from 5-chloro-2-hydroxy acetophenone and aromatic amines. They

observed magnetic moments and electronic bands of the chelates with Schiff

bases of p-bromoaniline and 1-naphthylamine are suggested dimeric nature

and further suggested that one nucleus exist as square and other tetrahedral

e.g. (A) and (B).

36

O

Co

N

H3C Ar

N

O

CH3

Cl

Cl

(A)

O

Co

O

Co

N

NCl

Cl

R

R

CH3

H3C

Cl

Cl

(B)

R=

Br

Pereiro et al.261 reported the influence of cobalt complex on thermal properties

of poly(ethylene terphthalate) / polycarbonate. They denoted the effects of

processing time and concentration of cobalt acetyacetonate complex in polyethylene

terphthalate in thermogravimetric (TG) analysis.

Khot 2 reported cobalt complexes of substituted acrylophenone as examples of

complexes of β-diketone ligands as

OCo

O

CH3

OH

NO2

(a)

OCo

O

N(CH3)2

NO2

(b)

O O

O2N

CH3

Mohammad Shakir et al.262 reported 14 and 16-membered

hexaazamacrocyclic Co (II) complexes bearing pendant amine group with octahedral

geometry as-

NN

Co

N

N

N

N

NH2H2N ClCl

37

Syamal263 synthesized new ligands from salicylaldehyde and 5-methyl

pyrazole-3-carbohydrazide and reported Co(II) complexes with octahedral geometry

and dimeric structure.

Co

O

Co

O

O

NO

N

OH2

OH2

OH2

OH2

Prasad et al.264 also reported chalcone complexes with mixed ligands as

O

Co

O

O

OOH2

OH2

R1

R2

R1= H / MeR2= Et / Me

Venkateswar Rao265 reported the synthesis of tetradentated Schiff bases

derived from dehydroacetic acid (DHA and carbohybrazide and their complexes with

various transition metals like Co (II).

N

M

O

N

OOH2

OH2

O O

H3C CH3

O O

HN NH

O

CH3H3C

Venketeswer Rao266 have also reported the Schiff base complexes of

dehydroacetic acid and DL-Histadine with Co(II), V(IV), Ni(II), Mn (II), Fe (II) Cu (II)

etc.

Prasad et al.267 reported synthesis of mixed ligand complexes of Co (II)

containing 5-bromosalicyldehyde and β-diketone, hydroxyl aldehydes or ketones.

Structures obtained are as follows-

38

O

CoO

O

OOH2H

RBr

(a)

R=H,CH3, C2H5, C6H5

O

CoO

O

OOH2H

HBr

(b)OH2

O

CoO

O

O

RH

RBr

(c)

R= CH3, C6H5

Mathew et al.268 reported the synthesis and characterization of Co (II)

complexes of Chromen-2-one-3-carboxyhydrazide and 2-(chromen-2’-only)-5-

(aryl)1,3,4-oxodiazole derivatives.

Structure of metal complex of 1,3,4-oxodiazole-

N

Co

O

O

N

O

OX

Cl

ON

ON

NO2

O2N

X= Cl-/ Br-/ NO3/ CH3COO-/ ClO4-, CNS-/ SO4

Banergy et al.269 reported the synthesis and electrochemistry and single

crystal structure of [Co(α-NaiEt)2(N3)2] Where α-NaiEt=1-ethyl-2(naphthyl-α-

azo)imidazole.

Reaction:

Co(OAc)2+2α-NaiR+2NaN3NaOH

Stir, 298oK[Co(N3)2(α-NaiR)2] + NaOAc

Where R= Me, Et or Bz

Structure of complex –

39

N'

Co

N

N

N'N3

N3

Baranwal et al.270 reported the synthesis and characterization of novel mixed

ligands like ternary carboxylato complexes of Co (II) with Schiff bases HSB having

general formula [Co(OOCR)SB], where R= C11H23, C13H27, C15H31 or C17H35 etc.

Co Co

O O

OO

O N

N O

C6H4

H4C6

R

R

Ar

Ar

O

O

H

Et

Et

H

Ar=Ph / p-Cl-C6H4R=C11H23/ C13H27/ C15H31/ C17H35

Demirhan et al.271 reported the synthesis and characterization of a new vic-

dioxime ligand and its complexes with Co (II). Systematic studies of substituted

derivatives of 1, 10 phenanthroline (Phen) and other α-diimines have been

successfully undertaken272. Nebahat gave the synthesis of a new Vic-dioxime (I) and

its reaction with various metal ions like Co (II).

e.g. synthesis of 5,6-diamino-1,10 phenanthrolino-5-6-bis(2,3-dihydroxyimino-1-aza)

propane prepared, from anti-chloro-methyl dioxime and 5,6 diamino-1,10

phenanthroline to give the Co (II) complex.

40

N

N

NH2

NH2

C

C

H3C

H3C

N

N

OH

OH

NaHCO3N

N

NH

NH

C

C

N

N

CH3

OH

NN

OH

CH3

NOH

NHO

vic-dioxine

2

Co (II) structure obtained is a dimeric species of the polymeric compound as-

N

N

HN

HNN

N

Co

NH

NHCl

Cl

N

Co

N

N

NCl

Cl

CH3H3C

OH

OH

OH

OH

N

Co

N

N

N Cl

Cl

H3CCH3

HO

OH

HO

OH

Khatavkar et al.273 reported the structural investigations of Co (II), Cu (II) and

Ni (II) complexes of phenylazobenzoylacetone.

Awadallah et al.274 reported the synthesis and biocidal activity studies on solid

complexes of Co (II), Fe (II) and Ni (II) with Violuric acid and dinitrosoresorcinol. It

was found that most of the compounds possessed fairly good antibacterial and

antifungal activities.

Panda et al.275 reported the synthesis and characterization of Co (II) with [16]

1,5,6,8,9,13,14,16-octaaza-2.4,10,12-tetraoxo-7,15-dithia-

1,3,3,5,6,8,9,11,11,13,14,16 dodecahydrocyclohexadecane.

41

HN

HN NH

Co

NH

NH NH

NHNH

SS

OO

OO

x-

x-=Cl-/ Br-/ NO3-/ SO4

2-

Singh et al.276 reported synthetic and spectroscopic studies of Co (II)

complexes of pyridine-2-carboxaldehyde thiobenzoyl hydrazone denoted as 2-PTBH.

HN N

S

N

Structure of complexes

N

S N

SM

N

N

N

N

b) [Co(2-PTB)2

S

N S

N

CoNH

HN

N

N

x

x

a) Co (2 PTBH)2 X2, where X =Cl, Br, NCS

HC

CH

Binzet et al.277 reported the synthesis and thermal behavior of Co (II) Ni (II)

and Cu (II) complexes of N, N-di-n-propyl-N’-(2-chlorobenzoyl) thiourea.

Mathews et al.278 reported synthesis and characterization of the complexes of

Co (II) Ni (II), Cu (II) anf Zn (II) with 2-(2-carboxyphenylazo)-1,3-diketones like

acetylacetone, benzoylacetone and dibenzolmethane. The ligand exist entirely as

intromolecularly hydrogen bonded 2-aryl hydrozones and this form persists in metal

chelate in which the hydrogen bonded and deprotonated hydrazeno nitrogen atom

42

and one of the carboxylate oxygen atom bonds with metal ion leaving one of the

carbonyl groups free.

N OCo

O

NOH2

H3C

O CH3

O

Fahiman279 reported substituent effects on the volatility of metal β-diketones.

Volatile trends are established for a series of M (β-diketonate)n complexes , where

M= Cu (II), Co (II), etc and β-diketonate are i) (acac) i.e. acetylacetonate, ii) (tfac) i.e.

trifluoroacetylacetonate, iii) (hfac) i.e. hexafluoroacetylacetonate, etc.

Golding280, Hill et al.281, Abeles282 and Wilkinson283 reported preparation of the

models for vitamin B-12 or Cobaloximes.

e.g. Bis(dimethylglyoxime) ethyl-pyridine Co (III).

e.g. Dibromo(dimethylglyoxime) dimethylglyoxomatocabalt III.

CoBr2

N

N

CH3

CH3

OH

OH

2

O

N

Co

N

OH

N

OH

O

N

CH3

CH3H3C

H3C Br

Br

H

1.3.4 Brief account of nickel (II) complexes

Nickel is moderately abundant and is twenty second most abundant element in

the earth’s crust. Nickel is the member of‘d’ block of the periodic table having atomic

No-28, which is placed in I series of transition metals. The common oxidation state of

Nickel is (II) associated with d8 configuration. Though the chemistry of Ni (II) is simple

but complexes are quite complicated. Square planer and octahedral geometries are

commonly observed. Lee186 has given the account of few tetrahedral, trigonal

bipyramidal structures in his book named as “Concise Inorganic Chemistry”.

43

The square planer complexes with dsp2 hybridization are diamagnetic under

strong field forcing the electrons to pair up. Octahedral and tetrahedral Ni (II)

complexes are paramagnetic due to two unpaired electrons and are associated with

octahedral (sp3d2) and tetrahedral (sp3) geometries respectively.

Chondekar187 reported mononuclear Ni (II) complexes of Schiff bases derived

from 5-chloro-2-hydroxy-acetophenone and aromatic amines.

N

NiO

O

N

CH3

Ar

Ar

CH3

Cl

Cl

Baranwal et al.284 reported the synthesis and characterization of substituted

derivatives of Ni (II) carboxylates with Schiff bases. The complex is reported to

possess linear trimeric structure with each Ni (II) centre having octahedral geometry.

o o

o o

Nio

o

o

o

Ni

Ni o

o

o

o

oo = bidentate ligand

Shivakumaraiah et al.285 reported monochelates and bischelates of Ni (II) with

bis-benzimidazolyl derivatives.

The intention behind above study is the report of the binding of histidine

imidazole to Ni (II) in various biological centres given by Cammack286.

Nickel is an essential trace element present in many hydrogenases which is

reported by Van Der Zwaan et al.287. Sorell288 reported metal complexes of

44

multidentate Nickel-heterocycles containing imidazole moiety for metalloenzymes

and metalloproteins.

Brajesh Kumar et al.289 reported the physico-chemical and spectral studies of

Ni (II) complexes of 2-subtituted benzaldehyde semicarbazone and

thiosemicarbazones the chemistry of which is receiving considerable attention due to

their pharmacological properties. Padhye et al.290 reported a wide range of medicinal

properties of semicarbazones and thiosemicarbazones and their metal complexes.

Hussain Reddy291 reported the synthesis and characterization of Ni (II)

complexes of some heterodonor ligands like 2,4-dihydroxyacetophenone-2-imino-

ethanethiol (DAET) etc.

C

CH3

N

SHOHHO

Structure of complex (binuclear)

N

X X

X

N

X

Ni Ni

OH2

OH2

OH2

OH2

X= O or S

Manimekalai et al.292 reported the studies on Ni (II) complexes of

benzoylhyrazones, They synthesized Ni (II) complexes of the type [NiLOH.

2H2O]2.nH2O, where L is either Cis-2,6 diphenyltetrahydrothiopyran-4-one benzoyl-

hydrazone. i.e. DTTBH

Structure of DTTBH-

S

NNH

O

Ph

Ph

Or trans-3-methyl-cis-2,6 diphenyl piperidine-4-one benzoylhydrazone i.e.

MDPBH.

Structure of MDPBH-

45

HN

NNH

O

Ph

Ph

CH3

Metal complexes of aroylhydrazone have broad application in biological

processes, such as in the treatment of tumour, tuberculosis, leprosy and mental

disorder293, 294.

Ligands DTTBH and MDPBH react in the enol form with metal ions. For Ni (II)

complexes enolic oxide bridged dimeric strucuture has been proposed.

Ni

O

Ni

ON

N C

N

NC

S

S

OH2

OH2

HOOH2

OH2

OHPh

PH

H

H

Ph

Ph

4 H2O

Waldemar Adam et al.295 reported a convenient synthesis of Ni (II) and Co (II)

complexes of unsymmetrical salen-type ligands and their application as catalysts.

Salen-type ligands with N and O atoms are important as their metal complexes find

widespread applications as homogenous catalysis in variety of reactions296 e.g. use

of Ni (II) complexes as highly active for polymerization of olefins297.

Structure of complex

46

O

Ni

NHC

O

CHN

Xiaoyan et al.298 reported α, β unsaturated carbonyl compounds as Hard/ soft

chelating ligands in methyl Nickel phenolates and investigated the structure of trans-

methyl-2-(3-phenyl-2, 3-η-2-propenoyl) phenolato bis (trimethylphosphine) Nickel (II)

complex.

Biradar299 reported synthesis and characterization of complexes of Ni (II) with

O,O’ dihydroxychalcones.

Chaston300 et al. reported thioderivatives of β-diketones and their Nickel (II)

chelates.

1.3.5 Brief account of copper (II) complexes

Copper is one of the ancient metals used by human being in his evolution. It is

one of the most transition element from first row of d-block of the periodic table. It is

moderately abundant and is the twenty fifth most abundant elements in the earth’s

crust. Copper is extensively studied for complexation with its most stable oxidation

state259 as 2+.

Cu (II) ion with d9 configuration provides an opportunity for observation of the

Jahn-Teller effect associated with additional stabilization besides crystal field

stabilization energy (CFSE). Number of Cu (II) complexes with bidentate ligands

containing O and Nickel donor atoms has been reported by Tan301 and

Chondhekar302.

They found to have square planer, tetrahedral and octahedral geometries.

In our laboratory Chondhekar302 reported both mononuclear and binuclear

Copper (II) complexes of Schiff bases derived from 5-chloro-2-hydroxy

acetophenones and aromatic amines e.g. A and B.

47

O N

Cu

ON

R

R'

R'

R

Cl

Cl

(A)

Cu

OCu

O

N

NR'

R

R'

R

Cl

Cl(B)

BrBr

Parashar et al.303 reported the Cu (II) complexes of salicyldahyde Schiff bases

with 2 substitutes aniline with square plane geometry.

O NCu

ON

R

R' R'

R'

Carugo et al.304 synthesized Cu (II) complexes of 4-hydroxy-6-methyl-3[3-

dimethylacryloyl]-2H-pyran-2-one. This complex is reported to have

pentacoordination with square pyramidal stereochemistry having pyridine in the

apical position.

O O

O OCu

N

O

O

O

O

CH3N

N

H3C

48

Djedouni et al.305 reported Cu (II) complexes of Bis[3-acetyl-6-methyl-2-H-

pyran-2,4(3H)-dionato]bis(dimethyl suphoxide) i.e. [Cu (C8H7O4)2(C2H6OS)2].

The complex shows Cu (II) ion octahedrally co-ordinated with the type MO6.

The bidentate dehydroacetic acid ligands occupy the equatorial plane of the complex

structure in trans configuration and DMSO is co-ordinated through O at apical

positions.

O

Cu

O

O

O

OMe2

OSMe2

O

O

H3C

CH3

O

O

CH3

H3C

Mishra et al.306 reported synthesis, spectroscopic studies, molecular, structure

optimization and superoxide dismutase of Cu (II) and Zn (II) bipyridyl assisted

supramolecular motifs containing octadentate Schiff base. Structure of [ Cu2

(bipyridine)2. tsdb] complex , where tsdb=N, N’, N”,N’”-tetrasalicylidene-3,3’-

diaminobenzidine.

N N

N NCu

O

ONN

NN

O

O

Cu

Salunke-Gawali et al.307 reported thermal magnetic and electro-chemical

properties of polymeric copper complexes of 2-hydroxy-1-4-naphthalo-quinone and

its methyl derivative.

Shahada et al.308 reported synthesis, characterization and thermal studies of

new chelating Fulven monomers, polymers and their metal complexes e. g. Cu (II).

49

Mokerrem Kurtoglu et al.309 reported synthesis , characterization and biological

evaluation of Cu (II), Co (II) and Ni (II) complexes of Schiff base-b m b H i.e. 4-[{4-

(benzyloxy) phenyl]-imino} methyl] benzene-1, 3-diol.

Structure of the complex-

O

Cu

N

N O

OH

OH

O

O

Gulnur Keser Karaoglan310 reported synthesis and characterization of a new

Schiff bases namely-2-(6-(E)-1-(2-hetadecylcarbonyl-oxyphenyl)

methylideneamino)[1, 10] phenanthrolin-5-yl-imino methylphenyl sterate with Cu (II),

Ni (II) and Co (II) salts.

Structure of the complex-

O

Cu

N

ON

OO

C17H35

C17H35

H

H

N

N

50

Shriver311 denoted the use of Cu (acac)2 complexe in the method of chemical

vapour deposition (CVD) in order to prepare thin films needed for the

superconductors in electronic devices.

Nakamura312 reported the method stabilizing β-diketone metal

complexes and their compositions for metalorganic CVD.

O

O

M

R1

R2 n

M= Cu, Mn, Zn, Co, Mg etc.

R1 & R2=alkyl group

n>0

Devi et al.313 reported the synthesis, characterization and chemical vapor

deposition of a novel Cu (II) chemical vapor precursor.

Fahiman et al.279 reported substituent effects on volatility of metal β-diketones.

Volatile trends are established for a series of M (β-diketonate) n complexes, where

M=Cu (II), Co (II), While β-diketonates are acetyacetonate (acac);

trifluoroacetylacetonate (tfac) or hexafluoroacetylacetonate (hfac).

Teghil et al.314 reported the thermodynamic study of the sublimation processes

of Cu and Al acetylacetonate.

51

1.3.6 Literature Survey of Emine Complexes with Metals

Literature survey revealed that enamines or ketoenamines can be subjected to

different reactions and substituted products are obtained.

Fanshawe et al.315 reported substituted enaminoketones. They claimed for

substituted enaminoketones of the formulae.

O

NH2

R

and

NH2

O

R

Where R is selected from the group consisting of pyridyl and pyrazinyl.

Yong-Ming et al.185 reported the transformation of β-bromodifluoromethyl β-

enaminoketones.

Endo Kohel et al.316 reported addition of Zn salts of stabilized cabanion

species to isolated olefins. They described the deprotonation reaction of

enaminoketones, which were available from 1, 3dicarbonyl compounds was

foundwith an equimolar amount of dialkylzinc under mild conditions. The resulting

organozinc reagents react with a cyclopropenone acetal to afford a carbometalation

product in high yield.

Gerhard et al.317 reported the synthesis of enaminoketone sulphides of the

formula-

O N

R1

SPh (Y)y

R2

R3

R4

Where R1, R2, R3 and R4 = alkyl or hydrogen.

Y= halogen, alkoxy, alkyl, nitro or cyano group

y = integer ranging from 0-3.

Larina et al.318 reported the use of enaminoketones and enhydrazides in the

synthesis of phosphorus-nitrogen containing heterocycles and Phosphorylated

enamines.

52

The scheme given by Larina can be established that 4-arylamino-3-penten-2-

ones react with phosphorus pentachloride to form 4-Nickel-aryl, Nickel-

dichlorophosphyrylamino-2-chloro-1,3-

pentadienyltrichlorophosphoniumhexachlorophosphorates I. Compound I as well as

diphosphoric acid chloroanhydride II readily prepared from compound I undergo

heterocyclisation to 1,2, azophosphine III and IV with cleavage of phosphorous

chloride.

NH

R O

Ar3PCl53HCl N

Cl3P

R Cl

Ar

POCl2(I)

PCl6-

-POCl3

NP+

RCl

Ar

(III)Cl Cl

2 HCOOH

-POCl3-4HCl

-2CO

N POCl2

RCl

Ar

POCl2(II)

-POCl3

NP

RCl

Ar

(IV)O Cl

Ar= Ph, p-MeC6H4 p-NO2C6H4R= H, Me

No references cited for enamines enaminoketones complexes with metals.

53

1.4 AIM OF THE PRESENT INVESTIGATION

Bacon F. in 1620 stated that “Those who aspire not to guess and divine, but to

discover and know, who propose not to devise mimic and fabulous worlds of their own, but

to examine and dissect the nature of this very world itself, must go facts themselves for

everything”319.

-

-

-

-

“What is Chemistry?” The answer lies in the significance of each letter forming

the word ‘CHEMISTRY”-

Such as:

C - Curiosity

H - Honesty

E - Enthusiastic efforts

M - Magnificent

I - Infinity / Intelegence

S - Search

T - Truth

R - Real

Y - Yearn

Therefore “Chemistry can be defined as an intelegent efforts and honest yearn

originating from curiosity for better understanding of infinite journey of nature, which

results in the search for real truth lieing at the very root of the universe”.

� � �

54

“Where is Chemistry?”. Answer is ‘Chemistry is everywhere, right from atom

to universe. Therefore, it can be given that “chemistry is omnipresent similar to vital

force of universe (Vishva-Chaitanya) or God. There is no place without chemistry. The

concept of earth, fire, water, wood and sky (Panch Mahabhute) is full of chemistry

which is composed of elements and uncountable number of their compounds.

Inorganic chemistry is the important basic branch of chemistry, which has

experienced and impressive renaissance. Academic and industrial research in

inorganic chemistry is flourishing and the output of research papers and reviewers is

growing exponentially320.

Large areas of inorganic chemistry remain unexplored, so new and often

unusual inorganic compounds are constantly being synthesized in laboratories. Such

exploratory inorganic syntheses, especially in co-ordination chemistry continue to

enrich the field with compounds that give us new perspectives on structure, bonding,

reactivity and biological activities. In addition to its intellectual attractions, we can

learn that inorganic chemistry has considerable practical impact and touches on all

other branches of science. e.g. In industrial field, eight of the top ten industrial

chemicals by weight are inorganic. Inorganic chemistry is also essential to the

formulation and improvement of modern materials such as catalysts, semiconductors,

superconductors, light guides, non-linear optical devices and advanced ceramic

materials. The environmental impact of inorganic chemistry is huge. In this

connection the extensive role of metal ions (especially transition metals such as Fe,

Co, Ni, Cu, Mn, Cr, Zn, Mo etc) led to the triving area of bioinorganic chemistry which

may be extended upto biotechnology and genetic engineering311.

Bioinorganic chemistry is a leading discipline in which many critical processes

require metal ions including respiration, metabolism, nitrogen fixation,

photosynthesis, nerve transmission, muscle contraction, signal transduction and

protection against toxic and multigenic agents. Unnatural metals have been

introduced into human biology as diagnostic probes and drugs. Numbers of

biomolecules are co-ordination compounds formed from metal ions with organic

groups321.

55

This inspired for the search for the synthesis of organic ligands and

their transition metal chelates. Among the different functionalized chromones, 3-

formylchromones occupy an unique position because they can be transformed into

various heterocycles169.

Studies on co-ordination chemistry behavior of potentially important

ligands containing various organic functional groups with transition metals are a

subject of interest. The development of numerous organic chelating ligands that can

co.ordinate with transition metal ions has opened up a broad scope to research. The

transition metal complexes of bidentate to polydentate organic chelating ligands

containing oxygen-oxygen (e.g. chalcones, β-diketones etc.), oxygen-nitrogen (Schiff

bases) or Nitrogen-sulpher–(thiosemicarbazides)-oxygen etc. are proved to be the

potential donor sites have been reported.

3-Formyl chromones i.e. 4-OXO-4H-[1]-benzopyran-3-carboxaldehyde is a

versatile synthone i.e. precursor for number of compounds like pyrazoles oxazoles,

pyrimidines enamones etc. Upon condensation with different nucleophiles.

These 3-formylchromones give important intermediates, which can be used for

the synthesis of some important heterocyclic compounds of metal complexes.

Compounds having chromone moiety are associated with interesting biological

activities170 associated with this nucleus are antibacterial, antifungal, antidiabetics. In

chromone, substituents at 2 and 3 positions have been reported to possess coronary

dilatory relaxation activity, muscular relaxation effect, antimicrobial and analgesic

activity.

When 3-formylchromones are refluxed with piperidine in ethanol, gave 1-(2-

hydroxyl-phenyl)-3-piperidin-1-yl-propenone i.e enaminoketones.

OH

O

N

It is planned to undertake comprehensive investigation of transition

metal complexes of enaminoketones. The work includes synthesis of variously

substituted ligands derived from 3-formylchromones and piperidine as-

56

[1]-1-(2-hydroxy-5-chloro-phenyl)-3-piperidine-1-yl-propenone-L1.

OH

O

NCl

[2]-1-(2-hydroxy-5-methylphenyl)-3-(piperidin-1-yl)prop-2-en-1-one-L2

OH

O

NH3C

[3] 1-(2-hydroxy-3,5-dimethylphenyl)-3-(piperidin-1-yl)prop-2-en-1-one-L3

OH

O

NH3C

CH3

[4]1-(3-chloro-2-hydroxy-5-methylphenyl)-3-(piperidin-1-yl)prop-2-en-1-one-L4

OH

O

NH3C

Cl

[5] 1-(3,5-dichloro-2-hydroxyphenyl)-3-(piperidin-1-yl)prop-2-en-1-one-L5

OH

O

NCl

Cl

With this aim in view, the present study deals with the synthesis of complexes

in solid state using transition metal ions like Mn (II), Fe (II), Co (II), Ni (II) and Cu (II),

with synthesized enaminoketones designated as L1, L2, L3, L4 and L5. The

characterization of ligands have been proposed to carry out using elemental analysis,

57

M.P., conductivity, IR, NMR and UV/ Visible spectral study. The characterization of

metal complexes of enaminoketone ligands have been proposed to carry out using

elemental analysis, M.P., conductivity, IR, NMR and UV/ Visible spectra, magnetic

susceptibility, TGA / DTA and X-ray powder diffraction study.

Ligands as well as complexes are also proposed for the study of the

biological activity, so as to confirm whether there is enhancement in this property of

ligands due to metal Co-ordination.

All these investigations are to be used for structural prediction of transition

metals complexes.

58

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59

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