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Spectrochimica Acta Part A 72 (2009) 399–406

Contents lists available at ScienceDirect

Spectrochimica Acta Part A: Molecular andBiomolecular Spectroscopy

journa l homepage: www.e lsev ier .com/ locate /saa

ynthesis, crystal structure, EPR spectra of doped VO2+ and Cu2+ ions inZn(ethylisonicotinate)2(H2O)4]·(sac)2 single crystal

˙brahim Ucarepartment of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, Kurupelit, 55139 Samsun, Turkey

r t i c l e i n f o

rticle history:eceived 1 March 2008eceived in revised form 24 August 2008ccepted 9 October 2008

eywords:n(II) saccharinate complex-ray crystal structurePR

2+

a b s t r a c t

The tetraaquabis(ethylisonicotinate)zinc(II) disaccharinate, [Zn(ein)2(H2O)4]·(sac)2 (ZENS) (ein:ethylisonicotinate and sac: saccharinate) complex has been synthesized and its crystal structurehas been determined by X-ray diffraction analysis. The magnetic environments of VO2+ and Cu2+ dopedZn(II) complex have been identified by electron paramagnetic resonance (EPR) technique. The titlecomplex crystallizes in monoclinic system with space group P21/c, Z = 4. The octahedral Zn(II) ion, rideson a crystallographic centre of symmetry, is coordinated by two monodentate ein ligands through the ringnitrogen and four aqua ligands to form discrete [Zn(ein)2(H2O)4] unit, which captures two saccharinateions in up and down positions, each through intermolecular hydrogen bonds. Cu2+ and VO2+ doped ZENSsingle crystals have been studied at room temperature in three mutually perpendicular planes. The

O

u2+ ground state wave functionR

calculated results of the Cu2+ and VO2+ doped in ZENS indicate that Cu2+ and VO2+ ion substitute with theZn2+ ion in the host lattice. The angular variations of the EPR spectra have shown that two different Cu2+

and VO2+ complexes are located in different chemical environments, and each environment contains twomagnetically inequvalent Cu2+and VO2+sites in distinct orientations occupying substitutional positions

ry higeen

wucautIpnlpcow

2

in the lattice and show veelectron of Cu2+ ion have b

. Introduction

The chemical and biochemical properties of saccharin, one of theest and most widely used artifical sweeteing agents [1–3], and itsompounds have been intensively investigated mainly due to itsuspected cancerogenic nature [4]. But it is now thought that sac-harin is safe at human levels of consumption. On the other handhe saccharin molecule contains imino hydrogen which is acidic inature and can easily be lost producing the anion (C7H4NO3S)−.his anion has several potential donor atoms such as imino nitro-en, one carbonyl and two sulphonyl oxygen atoms, which make theaccharinate anion very interesting and versatile polyfunctional lig-nd in coordination chemistry. Coordination of saccharinate withransition metal cations is generally in M–N form, whereas M–Onteractions is preferred in the case of alkaline and alkaline-earthaccharinates [5,6]. Additionally, saccharinate anion acts as a bridg-ng ligand in certain cases, through its N and O (carbonyl) atoms

7,8]. Besides, the presence of free saccharin in the crystal latticesf certain complexes has also been established [9,10].

Recently, we have initiated the crystallographic and magneticharacterization of mixed ligand metal saccharinate complexes in

E-mail address: iucar@omu.edu.tr.

2

usta

386-1425/$ – see front matter © 2008 Elsevier B.V. All rights reserved.oi:10.1016/j.saa.2008.10.013

h angular dependence. The ground state wave functions of the unpairedconstructed and type of the distortion has, then, been determined.

© 2008 Elsevier B.V. All rights reserved.

hich the saccharinate acts as a counter anion [11]. As a contin-ation of these studies, we have now prepared and thoroughlyharacterized a new Zn(II) complex containing two saccharinatenions together with ethylisonicotinate ligand. Owing to possiblese in pharmacology and evaluate it as a pharmacological agent,he detailed knowledge of its physical properties should be known.n this context, we have determined both structural and magneticroperties of ZENS. In order to obtain electron paramagnetic reso-ance (EPR) data, transition metal ions should be doped in the host

attice of ZENS as an impurity. VO2+ and Cu2+ ions are generally usedrobes to enter the lattice substitutionally in place of the divalentations [12–16]. When these ions form paramagnetic centres thenne can get information about the local symmetry. It is therefore,e have used VO2 and Cu2+ ions in ZENS and obtained the EPR data.

. Experimental

.1. General method

All chemical reagents were analytical grade commercial prod-cts. Solvents were purified by conventional methods. The EPRpectra were recorded using a Varian E-109C model X-band spec-rometer. The magnetic field modulation frequency was 100 kHznd the microwave power was around 10 mW. The single crystals

4 cta Part A 72 (2009) 399–406

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Table 1Crystal data and structure refinement for ZENS.

Formula C30H34N4O14S2ZnFormula weight 804.14Temperature (K) 297(2)Wavelength (Mo K�) 0.71073Crystal system MonoclinicSpace group P21/c

Unit cell dimensionsa, b, c (Å) 7.2491(3), 17.1178(7), 14.2394(6)

ˇ (◦) 102.842(3)Volume (Å3) 1722.75(12)Z 4Calculated density (g cm−3) 1.550� (mm−1) 0.908F (0 0 0) 832.0Crystal size (mm) 0.54 × 0.41 × 0.21� range (◦) 1.89–28.01

Index ranges −8 ≤ h ≤ 8−21 ≤ k ≤ 21−17 ≤ l ≤ 17

Reflections collected 38418Independent reflections 3375 [Rint = 0.065]Reflections observed (>2�) 3002Absorption correction IntegrationRefinement method Full-matrix least-squares on F2

Data/restrains/parameters 3375/6/250Goodness-of-fit on F2 1.050FRL

3

3

s

Fs

00 I. Ucar / Spectrochimica A

ere mounted on a goniometry and the spectra were recordedn three mutually perpendicular planes at 10◦ intervals at 298 K.he g values were obtained by comparison with a diphenylpicryl-ydrazyl sample of g = 2.0036. The IR spectra were recorded on aasco 430 FT/IR spectrometer using KBr pellets and operating in000–400 cm−1 range.

.2. Synthesis of [Zn(ein)2(H2O)4]·(sac)2 (ZENS)

Into aqueous solution of the corresponding Zn(II) acetate,Zn(OAc)2] (2 mmol, 20 mL) was added to an aqueous solution ofodium saccharinate (4 mmol, 20 mL). After stirring for 30 min,recipitates were filtered and washed with acetone to yield theompounds [Zn(saccharinato)2(H2O)4]·2H2O. An aqueous solutionf ethylisonicotinate (ein) (4 mmol, 20 mL) were added into aque-us solutions of these compounds (2 mmol, 20 mL), under stirring,nd the mixtures were allowed to stand at the room temper-ture. After a few days, well-formed crystals were selected for-ray studies. The single crystals of Cu2+ and VO2+ doped ZENSere also grown by slow evaporation of the saturated aqueous

olutions admixtured in stochiometric ratios with about 0.05%uCl2·6H2O and VOSO4·3H2O salts. The well-developed single crys-als of suitable sizes were selected for EPR investigation after aboutweek.

.3. X-ray crystallography

A suitable single crystals were mounted on a glass fiber and dataollection were performed on a STOE IPDSII image plate detectorsing Mo K� radiation (�= 0.71019 Å). Details of the crystal struc-ure are given in Table 1. Data collection: Stoe X-AREA [17]. Cellefinement: Stoe X-AREA [17]. Data reduction: Stoe X-RED [17].he structure was solved by direct-methods using SHELXS-97 [18]nd anisotropic displacement parameters were applied to non-ydrogen atoms in a full-matrix least-squares refinement based

n F2 using SHELXL-97 [18]. All carbon hydrogens were positionedeometrically and refined by a riding model with Uiso 1.2 times thatf attached atoms and remaining H atoms were located from theourier difference map. Molecular drawings were obtained usingRTEP-III [19].

ipZ[

ig. 1. The molecular structure of ZENS, showing the atom-numbering scheme. Displacemall spheres of arbitrary radii (dashed lines indicate the hydrogen bonds and �-� intera

inal R indices [I > 2�(I)] 0.028indices (all data) 0.032

argest diff. peak and hole (Å−3) 0.28, −0.38

. Results and discussion

.1. Crystal structure of ZENS

Fig. 1 shows the numbering scheme of the title complex and theelected bond distances and angles are listed in Table 2.

The Zinc(II) ion in ZENS is located on a crystallographicnversion centre and the asymmetric unit consists of a com-lex cation together with one sac counter anion (Fig. 1). Then(II) ion is hexa-coordinated by four oxygens of aqua ligandsZn1–O: 2.112(1)–2.104(1) Å] composing the basal plane, and two

ment ellipsoids are drawn at the 40% probability level and H atoms are shown asctions, symmetry code (a) 1 − x, 1 − y, 1 − z).

I. Ucar / Spectrochimica Acta Pa

Table 2Interatomic bond distances (Å) and angles (◦) around the Zn(II) ion and hydrogenbonding interactions in ZENS.

(a) Bond lengths, bond angles

Bond lengths (Å)O1–Zn1: 2.112(1) O2–Zn1: 2.104(1) N1–Zn1: 2.147(1)N2–S1: 1.620(2) N2–C9: 1.354(2) C6–O4: 1.203(2)

Bond angles (◦)O2–Zn1–O1: 87.98(6) O2–Zn1–N1: 90.90(5) O1–Zn1–N1: 92.38(5)O1–Zn1–O2a: 92.02(6) O1–Zn1–N1a: 87.62(5) O2–Zn1–N1a: 89.10(5)C9–N2–S1: 111.16(12) O7–S1–O6: 115.43(10) O7–S1–N2: 110.60(10)

(b) Hydrogen-bonding interactions (Å, ◦)

D—H· · ·A D—A H· · ·A D· · ·A D—H· · ·AO1–H1A· · ·N2b 0.85(2) 2.23(2) 3.05(2) 164(2)O1–H1B· · ·O5a 0.85(2) 1.85(2) 2.70(2) 173(2)O2–H2A· · ·O4c 0.83(2) 1.95(2) 2.77(2) 170(2)O2–H2B· · ·N2a 0.80(2) 2.08(2) 2.88(2) 177(2)

t2hg[[[[22[[aeiw

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a Symmetry codes: 1 − x, 1 − y, 1 − z.b Symmetry codes: x − 1, y, z.c Symmetry codes: x, −y + 1/2, z + 1/2.

rans nitrogen atoms from the monodentate ein ligand [Zn1–N1:.147(1) Å] occupying the axial sites, adopting a distorted octa-edral sphere. The Zn1–Nein lengths in title complex are inood agreement with the corresponding distances reported forZn(na)2(H2O)4]·(sac)2 (na: nicotinamide) [Zn–N: 2.153(1) Å] [20],Zn(ina)2(H2O)4]·(sac)2 (ina: isonicotinamide) [Zn–N: 2.169(1) Å]11], [Zn(tea)2]·(sac)2 (tea: triethanolamine) [Zn–N: 2.104(1) Å]21], [Zn(pyet)2(H2O)2]·(sac)2 (pyet: 2-pyridylethanole) [Zn–N:.1417(8) Å] [22], [Zn(bpy)2(sac)(H2O)]·sac [Zn–N: 2.169(3) Å] (bpy:,2′bipyridine) [23] but slightly longer than those found inZn(mpy)2(sac)2] (mpy: 2-pyridylmthanol) [Zn–N: 2.0887(17) Å]24], [Zn(sac) (im) ] (im: imidazole) [Zn–N: 2.010(3) Å] [25]

2 2nd [Zn(sac)2(bzim)2]·2EtOH·H2O (bzim: benzimidazole, EtOH:thanol) [Zn–N: 2.032(3) Å] [25]. The Zn–Oaqua distances are sim-lar to those found in [Zn(ina)2(H2O)4]·(sac)2 [Zn–O: 2.1018(14) Å]

hile those distances are slightly shorter than those found in

yoa

Fig. 2. Three dimensional structure of ZENS. Dashed li

rt A 72 (2009) 399–406 401

Zn(pyet)2(H2O)2]·(sac)2 [Zn–O: 2.1417(8) Å] and [Zn(tea)2]·(sac)2tea: triethanolamine) [Zn–O: 2.156(1) Å] due most probably tohe hydrogen bonding interactions between the aqua and acceptorroups. The ring plane of ein nearly bisects the adjacent coordi-ation planes containing the octahedron axis. As expected, theolecular skeleton of the sac ions nearly planar in ZENS (rms devi-

tion of atoms from the mean plane of 0.0074 Å) and the N2–S11.620(2) Å] and N2–C9 [1.354(2) Å] bond distances are close tohose found in sodium saccharinate [26] and in the related sac-harinate complexes [22–25]. The bond angles of the metal-freeaccharinate ions in which the ring nitrogen is deprotonated as inhe title complex are in good agreement with those of the metal-onded saccharinato ligands such as [Cu(H2O)(py)2(sac)2] (I) [27]nd [Cu(na)2(sac)2(H2O)]·H2O (II) [28], showing that the metalonding to the ring nitrogen exerts little effect on the molecularimensions; for instance, the bond angle S–N–C = 111.2(2)◦ in ZENSTable 2) and the corresponding angles of 111.8(2)◦ and 112.1(2)◦ inI) and (II).

Analysis of the crystal packing indicates that there are twoype intermolecular hydrogen bond interactions (O–H· · ·O and–H· · ·N) in the complex, involving the oxygen atoms of aqua

igands, carboxylate group of ein ligand and saccharinate car-onyl oxygen and nitrogen atoms (Fig. 2, see Table 2 for details).part from these, there is also symmetry-unrelated weak slipping

ace to face �-� stacking interaction between the saccharinateS1–N2–C9–C10–C15, ring A) and pyridine ring of ein (ring B)Fig. 1). The centroid-to-centroid and centroid-to-plane distancesetween the rings A and B are 3.779(1) Å and 3.382 Å, respectively,nd dihedral angle between these ring planes is 7.740◦. The clos-st interatomic distance between these ring planes is (C4· · ·C15).506(3) Å.

.2. EPR investigation

EPR spectra of both Cu2+ and VO2+ doped ZENS single crystalsield many lines. The number and spacing of these lines werebserved to change rapidly with orientation. The lines appearingt one orientation disappear almost completely at some other

nes indicate the hydrogen bonding interactions.

402 I. Ucar / Spectrochimica Acta Part A 72 (2009) 399–406

tually

oaosgaTwac

3

otcstptCacpaEh

cTtTActu

gRbboac

Ttesdtgw

wdc

˛

ocotf

TP

C

I

I

P

Fig. 3. Variations of the g2 values of all lines in three mu

rientations, so it was very difficult to trace all of the lines inll orientations. Moreover, the line widths change slightly withrientation and the lines overlap frequently. Fig. 4 shows EPRpectra of VO2+ doped ZENS single crystals, while Fig. 3 gives the2 values of all detected lines, which is plotted against the rotationngle in three mutually perpendicular planes, for Cu2+ complex.he principal values g and A tensors and their direction cosinesere found by diagonialization procedure [29–31]. The results

re given in Tables 3 and 5 for Cu2+ and VO2+ ion doped ZENSomplexes, respectively.

.2.1. Cu2+ ions in ZENSTwo sets of Cu2+ complexes clearly identified in the EPR spectra

f Cu2+ doped ZENS single crystal, Table 3 and Fig. 3. This explainshat there are two different Cu2+ complexes located in differenthemical environments, and each having two magnetically distinctites. The intensities of all complexes seem to be almost equal whenraced in all orientations, which means that the formations of com-lexes are equally probable. From these results it is inferred thathere is magnetically inequivalent but chemically equivalent twou2+ ions in the unit cells of the ZENS single crystals. These resultsre consistent with the monoclinic symmetry properties. Hence, weonclude that the Cu2+ ion has entered the Zn2+ site in this com-lex taking also consideration that ionic radius of Zn2+ (0.74 Å) ispproximately enough for substitution of Cu2+ (0.72 Å). From thePR parameters (Table 3), we deduce that Cu2+ ions have an octa-edral environment with a rhombic distortion.

The EPR parameters of the crystalline powder sample indi-ate that the symmetry of the complex in the crystal is not axial.he partially resolved three components of powder EPR spec-rum is consistent with the results for the single crystals given in

able 3. The measured values are gxx = 2.140, gyy = 2.075, gzz = 2.380;xx = 41.1 G, Ayy = 59.2 G and Azz = 104.0 G. These values drive us toomment on the state of the unpaired electron knowing that whenhe ratio R(gxx − gyy)/(gzz − gxx) less than unity, it means that thenpaired electron is dominantly in the dx2−y2 state and when R is

oo

able 3rincipal g and A values of Cu2+ complexes in ZENS at room temperature.

omplex no Site gxx gyy gzz gi

-ZENS 1 2.140 2.075 2.382 2.2 2.140 2.076 2.383 2.

I-ZENS 1 2.129 2.050 2.373 2.2 2.180 2.045 2.335 2.

owder 2.140 2.075 2.380 2.

perpendicular planes of Cu2+ doped ZENS single crystal.

reater than unity, the unpaired electron is in the d3z2−r2 state. The-values for two chemically different Cu2+ complexes are found toe less than unity, so the ground state of the unpaired electron inoth complexes isdx2−y2 . In fact, when the site symmetry is rhombicr lower, the ground state will be neither d3z2−r2 nor dx2−y2 but andmixture of both [32,33]. The distortion can be pointed out morelearly by the ground state wave function of the central Cu2+ ion.

The d orbitals of a d ion split into a doublet Eg and a triplet of2g symmetry states in an octahedral crystal field. The base func-ions of Eg, are dx2−y2 and d3z2−r2 orbital, and the degeneracy of thenergy levels are removed in a distorted crystal field. When the siteymmetry is tetragonal the ground state is either d3z2−r2 or dx2−y2

epending on whether the distortion is compressional or elonga-ional [33]. When the site symmetry is rhombic or lower, then theround state is an admixture of these d orbital. So, the ground stateave function of Cu2+ ion can be written as

= [˛′2]1/2

[˛|x2 − y2〉 + ˇ|3z2 − r2〉] (3)

here ˛′2 is the probability of finding the electron in the metalorbital and it is a measure of the covalency. The normalization

ondition for mixing coefficients ˛ and ˇ is

2 + ˇ2 = 1 (4)

The ground state wave function parameters of Cu2+ ionsbserved in different environments are listed in Table 4. All the cal-ulations were made by using a simple computer program basedn Bhaskar Rao and Narayana expressions [34]. By using Table 4he ground state wave functions of the both in ZENS complex I areound to be

1 = (0.624)1/2[0.994|x2 − y2〉 + 0.109|3z2 − r2〉]

2 = (0.628)1/2[0.993|x2 − y2 + 0.114|3z2 − r2]

(5)

From these results, the covalency parameter ˛′2 = 0.624 obvi-usly explains that the unpaired electron spends 37.6% of its timen ligand orbital, whereas the rest is spent on the Cu2+ d orbitals for

so Hyperfine (G) R

Axx Ayy Azz Aiso

199 39.0 57.5 102.0 66.2 0.27199 37.0 59.0 101.5 65.9 0.27

184 31.5 49.1 108.5 63.1 0.66184 39.4 45.5 106.8 63.8 0.87

198 41.1 59.2 104.0 68.1 0.27

I. Ucar / Spectrochimica Acta Part A 72 (2009) 399–406 403

Table 4The ground state parameters for Cu2+ ion in ZENS single crystals at roomtemperature.

Complex no Site ˛′2 ˛ ˇ k

I-ZENS 1 0.624 0.994 0.109 0.6252 0.628 0.993 0.114 0.621

II-ZENS 1 0.669 0.994 0.109 0.5512 0.610 0.987 0.157 0.620

Powder-ZENS 0.623 0.994 0.102 0.632[Co(nic)2(H2O)4]·(sac)2 [46] 0.956 0.998 0.050 0.227[Ni(ina)2(H2O)4]·(sac)2 [47] 0.895 0.941 0.337 0.362[Zn(sac)2(H2O)4]·2H2O [48] 1 0.900 0.987 0.163 0.317[Zn(sac)2(H2O)4]·2H2O [48] 2 0.879 0.986 0.169 0.322[Co(ina)2(H2O)4](sac)2·1.5H2O [11] 1 0.531 0.981 0.195 0.720[Co(ina) (H O) ](sac) ·1.5H O [11] 2 0.580 0.969 0.247 0.657[[

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ldVlscemc

Ft

TP

C

I

I

2 2 4 2 2

Zn(ina)2(H2O)4](sac)2·1.5H2O [11] 1 0.626 0.966 0.260 0.599Zn(ina)2(H2O)4](sac)2·1.5H2O [11] 2 0.633 0.974 0.228 0.589

ic: nicotinamide; ina: isonicotinamide.

he site I. Similar results are also found for site II as given in Table 4.ince the coefficient of dx2−y2 is significantly grater than that of

3z2−r2 for both sites, one can conclude that the rhombic distortionriginates dominantly from d3z2−r2 orbital of the Cu2+ ion.

.2.2. VO2+ ions in ZENSVO2+ ion has the electronic configuration 3d1, which thereby

eads to paramagnetism in VO2+. The 51V nucleus (99.8% abun-ant) has a nuclear spin I = 7/2 with a large magnetic moment.O2+ impurities in ZENS single crystals yield EPR spectra with many

ines. Analysis of VO2+ doped ZENS single crystal spectra with the

imilar producers applied to Cu2+ complexes resulted in two VO2+

omplex sites. The complexes can be collected into two groups,ach having different chemical environments, and each having twoagnetically distinct sites, as in Table 4. The line intensities of two

omplexes located in different positions are about 4:1, which are

pptoa

Fig. 5. The powder EPR spectrum of V

able 5rincipal g and A values of VO2+ complexes in ZENS.

omplex no Site gxx gyy gzz

-ZENS 1 1.998 2.002 1.9232 1.970 2.017 1.936

I-ZENS 1 1.985 2.004 1.9102 1.988 1.997 1.919

ig. 4. EPR spectrum of VO2+ doped in ZENS single crystal. The magnetic field is inhe cb plane making 100◦ with the b axis.

roportional to populations of the different complexes (Fig. 4). The

owder spectrum of VO2+ doped ZENS recorded at room tempera-ure is shown in Fig. 5. One parallel and perpendicular componentsf the VO2+ complex are clearly resolved. EPR parameters are foundnd given in Table 5, confirming the single crystal results. The VO2+

O2+ doped ZENS single crystal.

giso Hyperfine (G)

Axx Ayy Azz Aiso

1.974 70.0 63.4 188.0 107.11.974 77.6 64.7 189.7 110.6

1.966 84.3 67.4 213.4 121.61.968 79.5 71.6 213.2 121.4

404 I. Ucar / Spectrochimica Acta Part A 72 (2009) 399–406

Table 6Spin-Hamiltonian parameters, Fermi contact terms and molecular orbital coefficients of VO2+ doped ZENS single crystals.

Complex no Site g‖ g⊥ A‖ (10−4 cm−1) A⊥ (10−4 cm−1) Aiso (10−4 cm−1) |R| (10−4 cm−1) ˇ22 k �g‖/�g⊥

I 1 1.923 2.000 175.7 62.4 100.1 132.2 0.92 0.78 34.02 1.936 1.993 177.4 66.4 103.4 129.7 0.93 0.82 7.10

I

P

iweAnr

lrttoaw[vuawV

at

A

A

TtbFptm

fg

P

lotaa

g

A

c

�

Ul�

ˇ

Ubfowsktsf

3

ow

3eahydrogen bonded. The relatively weak absorption bands between3025 and 3087 cm−1 are assigned to the�(CH) vibrations. The bandsdue to the stretching of the C O group of ein ligands were found at1685 cm−1. Regarding with the vibration modes of saccharinate, the�(C O) (1631 cm−1) stretching vibration shifts to lower energy than

Table 7Fermi contact term and molecular orbital coefficient of the vanadyl complexes invarious lattices.

Complex Site ˇ22 k Reference

I-ZENS 1 0.92 0.78 This work2 0.93 0.82 This work

II-ZENS 1 0.91 0.79 This work2 0.92 0.79 This work

Powder-ZENS 0.93 0.84 This work[Co(sac)2(H2O)4]·2H2O 0.91 0.78 [49]ZLT 1.00 0.86 [42]3CdSO4·8H2O 1.00 0.87 [41]

I-Cd(NH4)2(SO4)2·6H2O 1 1.00 0.85 [43]2 1.00 0.85 [43]

I 1 1.910 1.994 199.4 70.92 1.919 1.993 199.3 70.6

owder 1.932 2.001 183.2 70.1

on is known to form an octahedral complex and the V O directionill be predominant axial direction. The behavior of the unpaired

lectron in vanadyl complexes is determined by strong V O bond.s a result, both g and A values of all complexes are found to beearly axially symmetric as usual for most of the VO2+ complexeseported in the related studies [38,39].

The spectra show that VO2+ ion replaces the Zn2+ in the hostattice; since the V4+ is more active and smaller in size (the atomicadii are 0.74 Å for Zn2+ and 0.61 Å for V4+). VO2+ coordinates withhree H2O molecule in the equatorial plane of octahedron andwo ein groups are in the axial position of octahedron. VO2+ sitesccupy substitutional positions in the lattice with fixed orientationsnd show very high angular dependence. An octahedral complexith a tetragonal compression would give g‖ < g⊥ < ge and |A‖| > |A⊥|

34–36]. The deviation of g‖ and g⊥ values from the free electron galue and generally denoted by�g‖ and�g⊥, respectively. The val-es of �g‖/�g⊥ which measures the tetragonally of the VO2+ sitere calculated in ZENS and are given in Table 6. Referring to Table 6e can observe that �g‖/�g⊥ value is garter than unity, and theO2+ ions are more tetragonally distorted [37].

The parallel and perpendicular components of hyperfine inter-ction A‖ and A⊥ are related to the molecular orbital coefficients byhe following expressions [40]:

‖ = −P[� + 4

7ˇ2

2 + (ge − g‖) + 37

(ge − g⊥)]

(6)

⊥ = −P[� + 2

7ˇ2

2 + 1114

(ge − g⊥)]

(7)

he degree of distortion can be estimated from the Fermi contacterms k, and the P parameter, which are related to radial distri-ution of wave function of the ions given as P = gegNˇeˇN〈r−3〉. Theermi contact term is directly related to the isotropic hyperfine cou-ling and represents the amount of unpaired electron density athe nucleus, where P is the dipolar interaction constant between

agnetic moment of the electron and vanadium nucleus.Neglecting the second order effects and taking negative values

or A‖ and A⊥, P values are nearly calculated from Eq. (8) and areiven in Table 6 [35–37]:

= 7(A‖ − A⊥)6

(8)

The observed g values for most VO2+ complexes are generallyower than ge and the EPR data in the present work also support thisbservation. This lowering is related to the spin–orbit interaction ofhe ground state dxy level with low-lying excited state. The isotropicnd anisotropic (g and A) parameters can be determined from thenisotropic parameters, using the relations:

iso = 2g⊥ + g‖3

(9)

iso = 2A⊥ + A‖3

(10)

I

(V

113.7 149.9 0.91 0.79 11.1113.5 150.2 0.92 0.79 8.95

107.8 131.9 0.93 0.84 54.0

ombining the above equations with the Eqs. (6) and (7) one gets:

= −Aiso

P− (ge − giso) (11)

sing the Eq. (11), the value of Fermi-contact terms (�) are calcu-ated and given in Table 6. Combining Eqs. (6) and (7) and eliminateone can get an expression for ˇ2

2 in terms of g and A tensor values:

22 =

(−7

6

)(A‖ − A⊥P

)+

((ge − g‖) −

(154

)(ge − g⊥)

)(12)

sing the above equation, ˇ22 which is the covalence ratio of V O

onds, is calculated and is given in Table 6. The deviation of ˇ22

rom unity usually represents the degree of admixture of the ligandrbitals and increase by the degree of covalency ˇ2

2, found in thisork, clearly indicates that the bonding is nearly ionic and repre-

ents poor p bonding of the ligands. From Table 5, ˇ22 is higher than

and the deviation of k from unity in ZENS represents the degree ofhe admixture of the 4s orbital into dxy orbital. It may be due to lowymmetry of the ligand field. Table 7 compares k and ˇ2

2 obtainedor this lattice with other lattices.

.3. FT-IR investigation

The assignment of series of characteristic saccharinate IR bandsf Zinc(II) complex presented in Table 8, was made in comparisonith those of sodium saccharinate [26].

The broad and strong absorption (Fig. 6) bands centered at507 cm−1 characterize �(OH) vibrations of the aqua ligands. Thexistence of �(OH) bands close to 3500 cm−1 might be taken asn indication of that some of the aqua OH groups are very weakly

-Mg(NH4)2(SO4)2·6H2O 1 1.00 0.85 [43]2 1.00 0.85 [43]

NH4)2Mg(SO4)2·6H2O 0.91 0.86 [44]O(H2O)5

2+ 1.00 0.83 [45]

I. Ucar / Spectrochimica Acta Part A 72 (2009) 399–406 405

Fig. 6. The FT-IR spectra

Table 8Assignment of some characteristic IR bands of [Zn(ein)2(H2O)4]·(sac)2, comparedwith those of sodium saccharinate hydrate (band positions in cm−1).

Assignment (cm−1) Na(sac)·H2O [26] ZENS

�(OH) 3333 s, br; 3264 s 3507 s, br�(CH) 3080 vw; 3050 w; 3012 vw 3087 vw�(CH)py – 3025 vw�(CO)ein. – 1685 vs�(CO)sac 1642 vs; 1629 sh 1631 vs�(CC)py – 1590 s; 1482 w�(CC) 1590 s; 1555 vw; 1460 m 1455 s�s(CNS) 1336 m 1330 s�as(SO2) 1258 vs 1284 vs; 1245 vsı(CH) 1165 sh; 1118 s; 1051 m 1054 m�s(SO2) 1150 vs 1168 vs; 1153 vsı(CH)py – 1122 mRing breathing – 990 vw�as(CNS) 950 m 966 vso.p. ring defpy – 786 mı(CO) 794 w 748 sı(CCC) 677 m 678 sı(CCC)py – 651 mı(SO2) 610 m 601 sı(CNS) 543 w 555 s(CCC) 530 m 532 s

pos

th1aob1fc

S

tCCoFw

A

Dr

R

[

[

[[[[

[[

[[

[

[[[[[

[[

[[

[

y: pyridine, sac: saccharinate, ein: ethylisonicotinate, as: asymmetric, s: symmetric,.p.: out of plane, def: deformation, vs: very strong, s: strong, m: medium, w: weak,h: shoulder, vw: very weak, br: broad.

hat of its sodium salt indicating that this group is involved in strongydrogen bonding. The strong absorption bands between 1590 and455 cm−1 correspond to the�(C–C) vibrations of the aromatic ringsnd ethyl groups. The absorption bands of the CNS moiety of sacccur at 1330 and 966 cm−1. Both �as(SO2) and �s(SO2) vibrationands appear as two split bands centered at 1284, 1245 cm−1 and168, 1153 cm−1, respectively. No considerable changes observedor �(SO2) and �(CNS) vibrations indicating that saccharinate is notoordinated to metal ion.

upplementary data

Crystallographic data (excluding structure factors) for the struc-ure in this paper have been deposited with the Cambridge

rystallographic Data Centre as the supplementary publication no.CDC 642532. Copies of the data can be obtained, free of charge,n application to CCDC, 12 Union Road, Cambridge CB12 1EZ, UK.ax: +44 1223 366 033, e-mail: deposit@ccdc.ac.uk or on the webww: http://www.ccdc.cam.ac.uk.

[[[[

[

of complex ZENS.

cknowledgements

I would like to thank Prof Dr Orhan Büyükgüngör and Ass. Prof.r. Bünyamin Karabulut for the acquisition of XRD and EPR data,

espectively.

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