synthesis and characterization of p-nitrobenzoylpyrazolone-5...

Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 3(1):61-68(ISSN: 2141-7016)

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Synthesis and Characterization of P-Nitrobenzoylpyrazolone-5 and

Its Complexes of Manganese (II), Iron (III), Rhodium (III), Tungsten (VI) and Uranium (VI)

1Arinze, J.C., 1Daniel, N.E. and 2Ogwuegbu, M.O.C

1Department of Industrial Chemistry, Abia State University, P.M.B. 2000, Uturu, Nigeria.

2Department of Chemistry, Federal University of Technology, Owerri, Nigeria. Corresponding Author: Arinze, J.C ___________________________________________________________________________ Abstract The present study is aimed at the preparation of 1-phenyl-3-methyl-4-(p-nitrobenzoyl)-5-pyrazolone (HNPZ) by the benzoylation of 1-phenyl-3-methyl-5-pyrazolone (HPMP) with p-nitrobenzoyl chloride, the preparation of metal complexes of HNPZ with manganese (II), iron (III), rhodium (III), tungsten (VI) and uranium (VI) ions, the investigation of the modes of interaction between the metals and the ligand (HNPZ) in aqueous media using spectroscopic methods, the investigation of the structures and compositions of the metal complexes using elemental analysis, UV-visible and infrared spectroscopies. The study suggests that the ligand and metal ions formed neutral complexes of the general formular M(NPZ)n X (M = metal ion, NPZ = ligand anion, X = H2O Molecule, n = the number of ligand molecules that complexed to M). Mn (II) formed dihydrate bischelate, Mn(NPZ)2 2H2O; Fe (III) and Rh (III) formed anhydrous trischelates, M(NPZ)3, while W (VI) and U (VI) formed dioxo aquobischelates of the type, MO2(NPZ)2 H2O. The study also showed the formation of neutral octahedral complexes of Mn (II), Fe (III) and Rh (III), and pentagonal bipyramidal complexes of W (VI) and U (VI) with the HNPZ anion __________________________________________________________________________________________ Keywords: extraction, solvent, complexes, pyrazolones, ligands, metal ions __________________________________________________________________________________________ INTRODUCTION The chemistry of transition and inner transition metal complexes with acylpyrazolones and other pyrazolone derivatives in aqueous solutions have been studied by several workers (Ogwuegbu and Orji, 1997; Uzoukwu, Gloe, Duddeek and Rademacher, 2001; Marchetti, and Pettinari, 2005). These groups of metals have received greater attention because of their special applications, spectral and magnetic properties. Several complexing agents have been suggested for their (transition metals) extraction from aqueous media (Mickler, Reign and Uhlemann, 1995; Ogwuegbu, Oforka and Spiff, 1996), but the use of 4-acylpyrazolones has been dominant, because the 4-acylpyrazolones form metal chelates that are highly soluble in most organic solvents. The 4-acylpyrazolones form highly stable neutral metal chelates that are principally hydrophobic and have found applications as extractants for metals from aqueous solutions. They have also been found to be strong active pharmaceutical ingredients. The drugs containing pyrazolone nucleus are known to display diverse pharmacological activities such as anti-bacterial, anti-fungal, anti-inflammatory, analgestic and antipyretic properties (Raman, Raja, Joseph and Ohaveeth, 2007; Marchetti and Pettinari, 2005; Sarbani, Jyoti and Nalla, 2008). The pharmacological spectrums of pyrazolone compounds are very similar to those of aspirin and some other non-steroidal anti-

inflammatory agents (Mariappan et al., 2010). Of all the 4-acyl-5-pyrazolones in use, 4-benzoyl-3-methyl-1-phenyl-5-pyrazolone (HBMPP) forms most stable complexes with various metal ions and consequently have been used extensively as efficient extraction reagents (Ogwuegbu and Orji, 1997; Uzoukwu, 1997). Most of the published works on the metal complexes of pyrazolone have been with other substituted derivatives of the 1-phenyl-3-methyl-5-pyrazolone moiety (Okafor and Uzoukwu, 1993; Uzoukwu, Gloe, Duddeek and Rademacher, 2001), while there is little information on the usefulness of 4-p-nitrobenzoyl derivatives as precipitants and extractants (Ogwuegbu and Maseka, 1998; Ogwuegbu, 1999). MATERIALS AND METHODS Reagents: All the chemical reagents used were of analytical grade from BDH, Aldrich or M&B, and were used without further purification. Distilled deionized water was used in all the reagents and experiments that required water. Equipment: A Pye Unicam SP8-100 UV-Visible Spectrophotometer, a Nicolet 510 FT IR-Spectrophotometer (4000cm-1-400cm-1), a TOA HIM-208 digital pH meter, and an OHAUS PF-200 Electronic weighing balance.

Journal of Emerging Trends in Engineering and Applied Sciences (JETEAS) 3 (1): 61-68 © Scholarlink Research Institute Journals, 2012 (ISSN: 2141-7016) jeteas.scholarlinkresearch.org


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Preparation of the ligand (HNPZ) The ligand was prepared as described by Ogwuegbu (1998). The process involved the benzoylation of 1-phenyl-3-methyl-5-pyrazolone (HPMP) with p-nitrobenzoyl chloride. 17.60 g (0.10 M) of HPMP was dissolved in 75 ml dioxane with gentle warming in a 500 ml three-necked round bottom “quick fit” flask equipped with a magnetic stirrer, separatory funnel and reflux condenser. Calcium hydroxide (7.5 g, 0.10 M) was added to form a paste and followed by dropwise addition of nitrobenzoyl chloride (14.55 g, 0.103 M) within 2-5 minutes (which had previously been dissolved in 50 ml of dioxane). The mixture was continuously stirred and gently refluxed for 90 minutes till the yellow calcium complex was formed. It was allowed to cool and the calcium complex decomposed by pouring in 400 ml of chilled 3 M HCl, whereby cream crude nitrobenzoylpyrazolone precipitated. The crude product was recystallized from an ethanol-water mixture containing a little hydrochloric acid to destroy any undecomposed calcium complex. Preparation of the Metal Complexes The complexes of Mn (II), Fe (III) and Rh (III) with HNPZ was prepared by dissolving 1.65 g (5 mmol) of Mn(NO3)2.4H2O, 1.61 g (3.33 mmol) of NH4Fe(SO4)212H2O, and 0.88 g (3.33 mmol) of RhCl33H2O, respectively, in 100 ml warm water. Each of the Mn (II), Fe (III) and Rh (III) solutions was added dropwise with stirring to a 100 ml hot ethanol solution of 3.23 g (10 mmol) HNPZ, giving a metal-ligand ratio of 1:2 for Mn (II) and 1:3 for Fe (III) and Rh (III) complexes. For W (VI) and U (VI) complexes, 1.32 g (5 mmol) of Na2WO42H2O and 2.12 g (5 mmol) of UO2(CH3COO)22H2O, dissolved in 0.1 M HCl solution were treated as above with 3.23 g (10 mmol) HNPZ in 100 ml hot ethanol solution, giving a metal-ligand ratio of 1:2 for each of the W (VI) and U (VI) complexes. In all cases, the mixed solution was heated up to 60oC and allowed to cool to room temperature. The precipitate formed in each case [ pale-yellow coloured precipitate for Mn (II), wine-red coloured precipitate for Fe (III), light brown coloured precipitate for Rh (III), dirty–white precipitate for W (VI), and orange coloured precipitate for U (VI) ] was filtered, washed with 2:1 water–ethanol solution, air-dried, and stored in a desiccator over a fused calcium chloride. Under the aqueous condition, UO2

2+ and WO2

2+ ions were generated respectively from their salts, and they took part in the complexation reactions (Vartak and Jose, 1993; Tamhina and Herak, 1977). RESULTS AND DISCUSSION Shown below are the enol and keto-forms of our ligand, HNPZ. From the procedures of the preparations it was expected that the enol tautomer

(Fig.1) was produced, and took part in all the metal-ligand complexation reactions. Fig. 2 shows the representative structure of all the metal complexes prepared.

(a) Enol form (b) Keto form Fig. 1 Tautomeric structures of the ligand

Fig. 2 Structure of metal complexes, M(NPZ)n.XH2O M = Mn, Fe, Rh, W and U X no of H2O molecule n = no of HNPZ molecules that complexed to M n = 3 for Fe (III) and Rh (III), and X = 0 n = 2 for Mn (II), W (VI) and U (VI), and X = 2 for Mn and 1 for W (VI) and U (VI). The observed microanalytical data for C, H, N, and some physical properties of the ligand and metal complexes are listed in Table 1. The data in the table 1 reveal that the enolized ligand (fig. 1) and metal complexes (fig. 2) were synthesized, and that in the aqueous solution, the mode of interaction between the ligand and metal ions is in the mole ratio of 1:2 for Mn (II) , W (VI) and U (VI), and 1:3 for Fe (III) and Rh (III). The complexes conform to the general molecular formular M(NPZ)nXH2O, where n is the oxidation state of the metal (M) or the ligand number, X is the number of water molecules in Mn (II), W (VI) and U (VI) complexes. The chelation process leading to the formation of the metal complexes can be represented as the displacement of the enolic protons from ligand molecules as per the following equation: Mn+

(aq) + nHL (org) MLn (org) + nH+(aq) (1)

The expected octahedral structures of the metal chalets are shown below: (a) (b) (c) Fig. 3: Proposed structures of the metal complexes,


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Where L L= NPZ- anion.

Fig. 3(a): M =Mn (II) Fig. 3(b): M = Fe (III) and Rh (III) Fig. 3(c): M =W (VI) and U (VI) Octahedral structures were also expected for W (VI) and U (VI) (fig. 3c) (Sandell and Onishi, 1978; Tamhina and Herak, 1977; Vartak and Jose, 1973), but the microanalytical data suggest the presence of one coordinated water molecule (fig. 4). This is in agreement with the structures proposed by Housecroft and Sharpe, (2008) for related tungsten and uranium chelate.

Fig. 4: Structure of metal complexes, where M = W (VI) and U (VI)

Table 1: Physical and microanalytical data for ligand and metal complexes

Compound Molecular formular

Colour M.P (°C)

Yield % found C (%cald) H N

HNPZ C17 H13 N3 O4 Cream 165 84% 63.06 (63.16)

4.12 (4.02)

13.04 (13.00)

Mn (NPZ)2.2H2O Mn C34H28N6 O10 Pale-yellow 188 65% 55.61 (55.51)

3.85 (3.81)

11.53 (11.43)

Fe (NPZ)3 Fe C51 H39 H9 O12 Wine-red 286 88% 59.66 (59.71)

3.77 (3.80)

12.32 (12.29)

Rh (NPZ)3 Rh C51H39 N9 O12 Light-brown 283 56% 57.18 (57.08)

3.74 (3.64)

11.62 (11.75)

WO2(NPZ)2.2H2O WC34 H28 N6 O11 Dirty white 292 45% 46.31 (46.36)

3.08 (3.18)

9.45 (9.55)

UO2(NPZ)2.2H2O UC34 H28 N6 O11 Orange 230 89% 43.60 (43.68)

3.01 (2.99)

8.90 (8.99)

Solubility data of the metal complexes and the ligand listed in Table 2 reveals that the metal complexes are hydrophobic and showed remarkable solubility in acetone (except for W (VI) and U (VI) complexes), ethylacetate, ether, dioxane and higher alcohols. These active organic solvents probably completed the coordination sites in the hydrated complexes, resulting in the excellent solubility of such complexes in polar organic solvents. The advantage of these organic solvents is that the solvent molecules possess

lone pairs of electrons for possible donation, and can be used with some other inert organic solvents such as chloroform (CHCl3) and carbon tetrachloride (CCl4) as solvent mixtures for extraction of metal ions from aqueous solutions, especially for those metals that form hydrated complexes which do not have all the coordination sites saturated by the organic reagents (Ogwuegbu, Oforka and Spiff, 1996; Ogwuegbu and Orji 1997).

Table 2: Solubility profile for HNPZ and metal complexes

SOLVENT HNPZ

Mn (II) complex

Fe (III) complex

Rh (III) complex

W (VI) complex

U (VI) complex

Water is is is is is is Methanol is is is is is is Ethanol ss is is is is is Acetone vs vs vs vs ss ss Xylene vs is ss ss ss s Toluene vs is vs vs ss is Benzene vs ss vs vs ss s Cyclohexane is is is is is is Benzylalkohol vs vs vs vs vs vs Carbon tetrachloride ss is is is is is Chloroform vs ss vs vs s vs Dioxane vs vs vs vs vs vs DMSO vs vs vs vs vs vs Acetonitride vs vs vs vs vs vs Ethylacetate vs vs vs vs vs vs Amylalcohol ss ss ss ss ss ss Ether s vs vs vs vs vs Propan- 2-ol vs ss s s s s Hexan – 1- ol vs vs vs vs vs vs

Legend: is = insoluble, ss = slightly soluble, s = soluble, vs = very soluble Electronic Spectra The electronic spectra data listed in table 3 shows that the ligand and metal complexes absorb between

205 nm and 270 nm in the near ultraviolet region. No band in the visible region was observed for any of the metal complexes, except the Fe-NPZ complex (3 =


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480 nm). The ligand and its metal complexes have virtually identical absorption maxima at 1 and 2, and are ascribed to intra-ligand * transition. The slight bathochromic or red shift was observed at 1 and 2 of the metal complexes, which indicate chelate formation between HNPZ anion and the metal ions. The almost identical spectra of HNPZ and the metal complexes at 1 suggest that the - bonding system of the free nitrobenzoylpyrazolone is almost intact in the ligand anion of the metal complexes, indicating that there is no interaction between the metal ions and the -bonding system of the ligand.

Therefore, the coordination between NPZ- and metal

ions is through – bond formation between metal ions and the oxygen atom of the carbonyl group (C=O) of the ligand as shown in fig. 1. The broad absorption band (3 max) around 406 and 600nm observed for Fe (III) complex is assigned to ligand metal charge transfer (LMCT). Similar bands have been reported for Fe (III) complexes of 4-acylpyrazolones and related compounds (Uzoukwu, 1993). The UV–visible spectral data of the ligand and metal complexes are shown in figs. 5 to 10.

Table 3: Electronic spectral data for HNPZ and metal complexes

Infrared Spectra The IR spectral data of the ligand and metal complexes are found in Table 4. Table 4: The infrared spectral data for ligand and metal complexes and approximate assignments

HNPZ

(cm-1) Mn(II) complex (cm-1)

Fe(III) complex (cm-1)

Rh(III) complex (cm-1)

W(VI) complex (cm-1)

U(VI) complex (cm-1)

Assignments

- 3447 b - - 3425 b 3415 b OH of water 3442 b - - - - - OH of enol 3060 w 3111 w 3061 w 3115 w 3112 w 3111 w C H (aryl) 2671s 2668 s - - - - O H --- O 2552 m 2552 m - - - - OH --- O - - - - 2352 W - O–H of water 1699 vs - - - - - C=O of enol form of

diketone - 1696 vs 1600 w 1622 vs 1694 vs 1693 vs as C= O 1622 - 1605 vs 1608vs - - 1622 vs - as C= O 1542 vs 1543 vs - - - 1575 vs asC=C Pyrazole ring 1523-1501vs - 1525 vs 1522 vs 1520 vs 1524 vs vas C=C=C phenyl ring 1430 s 1431s 1479 m - - 1476m as CH3 1393 w - - - - - as CH3 1350 vs 1351vs 1349 vs 1342 vs 1350 vs 1349 vs s C = O 1312 vs - - - - 1301 vs s C = O 1294 - 1281vs 1293 vs - - 1294 vs - s C=C=C 1211 - 1128m - 1157m 1211m 1210 m - C-H 1111 – 1014 w 1110 w 1022 w 1106 m 1019 w 1117m C-H in Plane

deformation of monosubstituted phenyl ring

920 m 947m 944 m 92 0m 921m 925 m C-ph stretch - 878 m - - 879 m 867 s as O=M=O 848 s 801s 836 m 849 m - - CH3 rocking 788 -764 m - 759 w - - - C – H 744 m - 744 m - - C – H 717 vs 717m - - 1717m 1717m (M-O + chelate ring

deformation) - 569 m 624 m 599 w 603 w 624 w Chelate ring vibrations 562 – 514 s - - - 500 w 515 w Chelate ring vibrations - 453 w 515 w 501 w 471 w 445 w M-O

Legend: s - strong, m - medium , b - broad, vs – very strong, - stretching frequency , s – Symmetric stretching, as – asymmetric stretching frequency, - bending or deformation, - out-of plane bending.

compounds 1 max (nm)

E1 (L.mol-1cm-1) 2 max (nm)

E2 (L.mol-1cm-1) 3 max (nm)

E3 (L.mol-1cm-1)

HNPZ 205 7.5 x 103 260 1.2 x 104 - - Mn-NPZ 210 7.8 x 104 263 1.2 x 105 - - Fe-NPZ 215 4.8 x 105 270 7.4 x 105 480 2.6 x 104 Rh–NPZ 213 1.2 x 105 265 2.7 x 105 - - W–NPZ 207 3.4 x 104 268 4.9 x 104 - - U-NPZ 210 8.4 x 104 265 1.4 x105 - -


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The observed IR frequencies have been assigned by comparing published reports on 4-acylpyrazolones and their metal complexes ( Mickler, Reign and Uhlemann, 1995; Okafor and Uzoukwu, 1993) and other structurally related compounds (Kovatchoukova, Retta and Terfa, 1996; Bruno and Svoron, 2003). The IR spectrum of the keto–enol tautomer of the ligand shown in fig. 1 is taken as reference. The IR absorption spectra have been divided into three main spectral regions: 4000 - 1800 cm-1, 1800 - 1000 cm-1 and 1000 - 400 cm-1. 4000 – 1800 cm-1 region All the metal complexes, except for Fe (III) and Rh (III), showed broad absorption bands around 3447 - 3415cm-1 region (3447 cm-1 for Mn (II), 3425 cm-1 for W (VI) and 3415 cm-1 for U (VI) complexes), and have been assigned to OH of the adduct water molecules coordinated to the central metal ions or held in the crystal lattices of the complexes. The strong, but broad band at 3442 cm-1 of the ligand is assigned to the O–H frequency of the enol. A strong band between 2671 – 2552 cm-1 for Mn (II) complex is ascribed to the OH ---O frequency arising from the vibrations of –OH of the enol – keto forms of 1,3-diketones involved in the intramolecular hydrogen bonding. The OH --- O band is absent in the IR spectra of the Fe (III) and Rh (III) complexes. The band between 3061 – 3111 cm-1 for Mn (II), Fe (III), Rh (III), W (VI) and U (VI) complexes are assigned to the stretching frequency of C-H group of the coordinated HNPZ anions. Hallam (1963) and Okafor and Uzoukwu (1993) reported similar observations. These facts indicate deprotonation of the –OH group during chelating, and the formation of M-O bonds in place of –OH bonds in the metal complexes. The complete disappearance of the weak band due to OH group of the ligand in the IR spectra of the metal complexes suggests the deprotonation of the OH group during chelation and formation of M-O bond in the metal complexes. 1800 – 1000 cm-1 region The band spectra occurring at 1600 -1700 cm-1 region is due to C=O and C=C frequencies of the chelate ring. Studies on -diketones showed that C=O occurs at a higher frequency than C=C (Nakamoto, 1970; Uzoukwu, 1997). Electron donation from the substituent phenyl group decreases the double bond character of the bond between carbon and oxygen and decreases the stretching frequency especially in the 1694 cm-1 region. The spectra data listed in table 4 show shifts of C=O near 1699 – 1605 cm-1 in the ligand to absorption bands near 1696-1608 cm-1 in all the metal complexes (except in Fe (III) complex), attributed to asC=O, suggest that the carbonyl (C=O) group is involved in the chelation process. Bands due to C =C are known to be very sensitive to chelation in -diketones (OKafor, Uzoukwu, Hitchcock and

Smith, 1990). The indication that pyrazolone ring with its C=C bonding system (lebelled 4 and 5 in fig. 1 is involved in the chelation process through electron delocalization of the chelate ring as shown in fig. 2 is confirmed by the absorption band assigned to the pyrazole stretching vibrational frequency (C=O) from 1542 to 1501 cm-1 for the ligand shifted by about 43 cm-1 for Mn (II) complex, 25 cm-1 for Fe (III) complex, 22 cm-1 for Rh (III) complex, 20 cm-1 for W (VI) complex and 75- 24 cm-1 for U (VI) complex. All the metal complexes showed strong absorption bands around 1210 -1106 cm-1 region and have been assigned to C-H vibrational frequency resulting from bending vibrations in the molecule. The vibrational frequency modes observed between 1117 and 1014 cm-1 have been assigned to C-H in–plane deformation of the phenyl ring in the complexes. The comparison of the spectrum of the ligand with those of the metal complexes show that there is little or no shift in the above frequencies, indicating that the -system of the monosubstituted phenyl ring of the free ligand is not involved in the coordination with metal ions studied. 1000 – 400 cm-1 Region The vibrational frequency modes of interest in this region are those due to the chelate ring and metal–ligand vibrations. This region provides information on the effect of the 4 –acylsubstituent on the stability of the metal–oxygen bond. The presence of bands between 600-400 cm-1, which are typical of 1,3 diketonates, have been suggested as due to bonding to metals through the oxygen atom of the ligand (Hallam, 1963; Ogwuegbu, 1999). The vibration frequencies centred around 867 and 879 cm-1 are ascribed to O=M=O vibrations. The absorption bands between 624-569 cm-1 listed in table 4 are due to chelate and metal–oxygen vibrations that are absent in the spectrum of the ligand. The absence of these bands in the IR spectrum of the ligand signifies chelation. The weak bands in the IR spectra of the metal complexes appearing at 453 cm-1 for Mn (II), 515 cm-1 for Fe (III), 501 cm-1 for Rh (III), 471cm-1 for W (VI),445 cm-1 for U (VI) and absent in the IR spectrum of the ligand have been assigned to M-O of the metal complexes. The M-O stretching frequencies for chelates fellow the order: Fe > Rh > W >Mn >U, which is in the order of increasing atomic weights of the metals, except for manganese. The IR spectra of the ligand and metal complexes are shown in figs. 11 to 16. Suggested Names of the Metal Complexes

1. Diaquobis(1-phenyl-3-methyl-4-(p-nitrobenzoyl)pyrazolonato manganese (II), Mn(NPZ)22H2O.

2. Tris(1-phenyl-3-methyl-4-(p-nitrobenzoyl)pyrazolonato iron(III), Fe(NPZ)3.


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3. Tris(1-phenyl-3-methyl-4-(p-nitrobenzoyl)pyrazolonato rhodium(III), Rh(NPZ)3.

4. Monoaquobis(1-phenyl-3-methyl(-4-p-nitrobenzoyl)pyrazolonato dioxotungste (VI), WO2(NPZ)2H2O.

5. Monoaquobis(1-phenyl-3-methyl-4-(p-nitrobenzoyl)pyrazolonato dioxouranium(VI), UO2(NPZ)2H2O.

CONCLUSION The elemental analysis, UV–visible and IR spectral studies on the 1-phenyl-3-methyl-4-(p-nitrobenzoyl) pyrazolone-5 (HNPZ) and its complexes of Mn (II) , Fe (III), Rh (III), W (VI) and U (VI) suggest that the HNPZ formed neutral complexes with the metal ions and that their structures conform to the types shown in figs. 3 and 4. The results also suggest octahedral configurations for Mn (II), Fe (III) and Rh (III) complexes, in which water molecules take up two positions of the octahedron in Mn (II), while Fe (III) and Rh (III) complexes are coordinatively saturated with the ligand molecules. The configuration in the metal complexes of W (VI) and U (VI) is pentagonal bipyramidal, consisting of four oxygen atoms from the 4-nitrobenzoylpyrazolone anions, two oxygen atoms from the uranyl and tungstenic ions and one oxygen atom from one water molecule. Only one water molecule directly coordinated to the central metal atom, though some authors had suggested that the water molecules are held in the crystal lattice of the complex or hydrogen bonded to it. The bonds between HNPZ and a metal ion are formulated as –bonds formed through the carbonyl and hydroxyl groups of the keto-enol form of the ligand. ACKNOWLEDGEMENT The authors are grateful to the third world Academy of Sciences for sponsoring one of the authors to the University of Beones Aires, Republic of Argentina, where these experiments were performed. We are also grateful to the Abia State University, Nigeria and the Copperbelt University, Zambia for their support and permission to the author to access the sponsorship at Argentina. REFERENCE Bruno, T. J. and Svoron, P. D. N. (2003). Handbook of Basic Table for Chemical Analysis, 2nd ed., CRC Press, London. pp. 319-406. Hallam, H. E. (1963). Infrared Spectroscopy and Molecular Structure, Davies, A. (ed.), Elservier, London. p. 415. Housecroft C. E. and sharpe, A. G. (2008). Inorganic Chemistry, 3rd ed., Pearson Education Limited, Harlow, England. pp. 703, 873.

Kovatchoukova, O. Retta, N., Terfa, A. (1996). Dinuclear Metal Complexes Derived from a Bis-chelating Heterocyclic Ligand, Bull. Chem. Soc. Ethiop. 10: 39. Mariappan, G., Saha, B. P. Sutharson, L. Garg, S. Pandey, L., Kumar, D. (2010). The Diverse Pharmacological Importance of Pyrazolone Derivatives: A review, Journal of pharmacy Research. 3(12): 2856-2859. Marchetti, F., Pettinari, R. (2005). Acylpyrazolone Ligands: Synthesis, Structure, Metal Coordination Chemistry and Application, Coord. Chem. Rev. 249: 2909-2945. Mickler, W., Reign, A. and uhlemann, E. (1995). Extraction of Zinc with Long-chain -dikitones and 4-acyl-5-pyrazolones, Septn. Sci. Technol. 30(12): 2588 – 2592. Nakamoto, K. (1970). Infrared Spectra of Inorganic and Coordination Compounds, Wiley, New York. pp. 247 - 256. Ogwuegbu, M. O. C., Oforka, N. C. and Spiff, A. I. (1996). Enhanced Extraction of Ni (II) with 3–methyl-4-(P–nitrobenzoyl)-5-oxo-1-phenylpyrazole in the Presence of Benzyl Alcohol, S. Afr J. chem. 49 (1/2): 26 - 30. Ogwuegbu, M. O. C. and Orji, E. (1997). Liquid-liquid Separation of U(VI) and Ni(II) by a Substituted Oxo–pyrazole, Minerals Engineering. 10(II): 1269 – 1278. Ogwuegbu, M. O. C. (1998). Physico–chemical Studies of 1– phenyl-3-methyl-4-(p-nitrobenzoyl) pyrazolone-5 and its Mg (II), Ni (II) and Cu (II) Complexes, Discov. innov. 10 (3/4): 256. Ogwuegbu, M. O. C. and Maseka, K. K. (1998). Studies on the Coordination Complexes of Calcium (II), Cadmium (II) and Tin (IV) with p-nitrobenzoyl-5-oxo-pyrazole, Bull Chem. Soc. Ethiop. 12(I): 28 -31. Ogwuegbu, M. O. C. (1999). Synthesis and Characterization of Nitroacyl-5-oxo-Pyrazole and its Vanadium (V), Iron (III) and Cobalt (II) Complexes, Bull chem. Soc. Ethiop. 13(2): 114 -117. Okafor, E. C., Uzoukwu, B. A., Hitchcock, P. B. and Smith, J. D. (1990). Pyrazolonate Complexes of Uranium: Urystal Structures of Bis-oxo–bis (1-phenyl-3-methyl-4-acetylpyrazol-5-onato) aquouranium (VI), Inorg. Chim. Acta. 172: 97 - 103.


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Okafor, E. C. and Uzoukwu, B. A. (1993). Adduct Coordination in U (VI) Complexes of 4-acyl Derivetives of 1-phenyl-3-methyl Phyrazolone-5: UV, IR and NMR Spectral Studies, Synth. React. Inorg. Met-org. Chem. 23 (1): 86 – 90. Roman, N., Raja, S. J., Joseph, J. and ohaveeth, U. R. J. (2007). Synthesis, Spectral Characterization and DNA Cleavage Study of Heterocyclic Schiff Base Metal Complexes, J. Chil. chem. Soc. 52: 1138. Sandel, E.B. and Onishi, H. (1978). Photometric Determination of Trace s of Metals: General Aspects, 4th ed., Part 1 Colorimetric Determination of Traces of Metals, John Wiley and Sons, New York. p. 957. Sarbani, P., Jyoti, M. and Nalla, S. D. (2008). High Speed Synthesis of Pyrazolones using Microwave–assisted Neat Reaction Technology, J. Braz. Chem. Soc. 19: 1590. Tamhina, B. and Herak, M. J. (1977). Solvent Extraction of W(VI) by 3-hydroxy-2-methyl-1-phenyl-4-pyridone, J. Inorg. Nucl. Chem. 39: 391-393. Uzoukwu, B. A., Gloe, K., Duddeek, H. and Rademacher, O. (2001).Crystal Structure of N,N’-ethylenebis(4-propyl-2,4-dihydro-5-methyl-phenyl-3H-pyrazol-3-onemine), Z. Kristallogr. NCS. 216: 451-452. Uzoukwu , B. A. (1997). Extraction Studies of Chromium (VI) from aqueous Solution with 1-phenyl-3-methyl-4-butylpyrazolone, Indian J. Chem., 36A: 351-353. Uzoukwu , B. A. (1993). Synthesis, UV, IR and NMR spectra studies of Mn (II) and Zn (II) Complexes of 1-phenyl-3-methyl-4-(benzoyl) pyrazolone-5, Spectrochim. Acta. 49A: 281 – 282. Vartak, D.G. and Jose, C. J. (1973). Stability Constants of the Complexes of Substituted 8-Amino-1-naphthols with UO2

2+, Cu2+, Ni2+, Co2+, Zn2+, Cd2+, Mn2+ and Mg2+, Indian J. of Chem. 11: 1506-1308. APPENDIX

Fig.5 electronic spectrum of HNPz

Fig.6 electronic spectrum of Mn (II)- NPz complex

Fig.7 electronic spectrum of Fe (III)- NPz complex

Fig.8 electronic spectrum of Rh (III)- NPz complex

Fig.9 electronic spectrum of W(VI)-NPz complex

Fig.10 electronic spectrum of U(VI)-NPz complex


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Fig.11 IR spectrum of HNPZ

Fig.12 IR spectrum of Mn(II)-NPz complex

Fig.13 IR spectrum of Fe(III)-NPz complex

Fig.14 IR spectrum of Rh(III)-NPz complex

Fig.15 IR spectrum of W(VI)-NPz complex

Fig.16 IR spectrum of U(VI)-NPz complex

synthesis and characterization of p-nitrobenzoylpyrazolone-5...

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