Spectrochimica Acta Part A 72 (2009) 11–16

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Spectrochimica Acta Part A: Molecular andBiomolecular Spectroscopy

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Structural characterization and EPR spectral studieson mononuclear copper(II) complex of saccharinwith ethylnicotinate

Ibrahim Ucar ∗, Esat Bozkurt, Canan Kazak, Ahmet BulutDepartment of Physics, Faculty of Arts and Sciences, Ondokuz Mayıs University, Kurupelit, 55139 Samsun, Turkey

a r t i c l e i n f o

Article history:Received 13 June 2007Received in revised form 26 June 2008Accepted 30 June 2008

Keywords:X-ray crystal structureEPR

a b s t r a c t

Mononuclear copper(II) saccharinate (sac) complex containing ethylnicotinate (enc), [Cu(enc)2(sac)2

(H2O)]·1.4H2O has been synthesized and characterized by spectroscopic (IR, UV–vis, EPR), X-ray diffrac-tion technique and electrochemical methods. It crystallizes in the tetragonal crystal systems with spacegroup I41cd and Z = 8. The copper(II) ion presents a CuN4O distorted square pyramidal coordination. Basedon EPR and optical absorption studies, spin-Hamiltonian and bonding parameters have been calculated.The g-values, calculated for title complex in polycrystalline state at 298 K and in frozen DMF (110 K),indicate the presence of the unpaired electron in the dx2−y2 orbital. The evaluated metal–ligand bondingparameters showed strong in-plane � and in-plane �-bonding. Some comparisons with related structures

IR

UV–visCyclic voltammetry

are made and the most important features of its IR spectrum were also discussed. The cyclic voltammo-gram of the title complex investigated in DMF (dimethylformamide) solution exhibits only metal centred

ntial

1

htfnioscabal

nmc[

c

aa

2

2

ustaogrU

1d

electroactivity in the pote

. Introduction

Saccharin (also known o-sulphobenzimide) and saccharinateave been studied in detail in several scientific contexts, due to bothheir commercial use in noncaloric food sweeteners and differentunctional groups such as the imino nitrogen, carbonyl and sulpho-yl oxygen [1–4]. The most common coordination mode of sac

s ligation through the negatively charged nitrogen atom, usuallybserved in the aqua bis(saccharinato) complexes of first-row tran-ition metals, and coordination via the carbonyl oxygen occurs inertain cases, especially with alkali, alkaline earth, inner-transitionnd p-block metals [4]. Additionally, saccharinate anion acts as aridging ligand in certain cases, through its N and O (carbonyl)toms [5–7]. Besides, the presence of free saccharin in the crystalattices of certain complexes has also been established [8,9].

In our ongoing research on determination of further coordi-

ation modes of saccharin with biologically important transitionetal ions, we have recently synthesized mixed–ligand metal (II)

omplexes of saccharinate and their structures have been reported10,11]. In this paper, we report the synthesis, structure, magnetic

∗ Corresponding author. Tel.: +90 3623121919 5255.E-mail addresses: iucar@omu.edu.tr (I. Ucar), esatb@omu.edu.tr (E. Bozkurt),

kazak@omu.edu.tr (C. Kazak), abulut@omu.edu.tr (A. Bulut).

sKAametIt

386-1425/$ – see front matter © 2008 Elsevier B.V. All rights reserved.oi:10.1016/j.saa.2008.06.046

range ±1.25 V vs. Ag/AgCl reference electrode.© 2008 Elsevier B.V. All rights reserved.

nd redox properties of new copper–sac complex with the enc lig-nd, namely [Cu(enc)2(sac)2(H2O)]·1.4H2O.

. 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 g-values werebtained by comparison with a diphenylpicrylhydrazyl sample of= 2.0036. The optical absorption spectra of title complex were

ecorded at room temperature in DMF solution on a CINTRA 20V–vis spectrometer working between 200 and 900 nm. The IR

pectra were recorded on a Jasco 430 FT/IR spectrometer usingBr pellets and operating in 4000–400 cm−1 range. An EcoChemieutolab-30 potentiostat with the electrochemical software pack-ge GPES 4.9 (Utrecht, Netherlands) was used for voltammetric

easurements. A three electrode system was used: a Pt counter

lectrode, an Ag/AgCl reference electrode and a Pt wire elec-rode as working electrode. The potentiostat/galvonastat have anR-compensation option. Therefore, the resistance due to the elec-rode surface was compensated throughout the measurements.

12 I. Ucar et al. / Spectrochimica Act

Table 1Crystal data and structure refinement for [Cu(enc)2(sac)2(H2O)]·1.4H2O.

Formula C30H28N4O12.4S2Cu

Formula weight 770.30Temperature (K) 297(2)Radiation (�) (Mo K�) 0.71073Crystal system TetragonalSpace group I41cdUnit cell dimensionsa, b, c (Å) 19.4308(7), 19.4308(7), 18.0312(10)˛, ˇ, � (◦) 90.00, 90.00, 90.00Volume (Å3) 6807.7(5)Z 8Calculated density (g cm−3) 1.5031� (mm−1) 0.833F(000) 3168Crystal size (mm) 0.35 × 0.28 × 0.25� range (◦) 2.10–27.14

Index ranges −24 ≤ h ≤ 24−24 ≤ k ≤ 24−23 ≤ l ≤ 23

Reflections collected 51746Independent reflections 3768 [Rint = 0.083]Reflections observed [I ≥ 2�(I)] 2848Absorption correction IntegrationRefinement method Full-matrix least-squares on F2

Data/restrains/parameters 3768/1/232Goodness-of-fit on F2 0.975FRL

Oe

2

[spcos

tf

2

cutrTahommido6torn[

3

3

FSc1t

Fs

inal R indices [I ≥ 2�(I)] 0.033indices (all data) 0.045

argest diff. peak and hole (eÅ−3) 0.29, −0.23

xygen-free nitrogen was bubbled through the solution before eachxperiment. All experiments were carried out at room temperature.

.2. Synthesis of [Cu(enc)2(sac)2(H2O)]·1.4H2O

Into aqueous solution of the corresponding Cu(II) acetate,Cu(OAc)2] (2 mmol, 20 mL) was added to an aqueous solution of

odium saccharinate (4 mmol, 20 mL). After stirring for 30 min,recipitates were filtered and washed with acetone to yield theompounds [Cu(saccharinato)2(H2O)4]·2H2O. An aqueous solutionf ethylnicotinate (enc) (2 mmol, 20 mL) were added into aqueousolutions of these compounds (2 mmol, 20 mL), under stirring, and

wg[td

ig. 1. The molecular structure of copper(II) complex, showing the atom-numbering schehown as small spheres of arbitrary radii (dashed lines indicate the hydrogen bonds and �

a Part A 72 (2009) 11–16

he mixtures were allowed to stand at room temperature. After aew days, well-formed crystals were selected for X-ray studies.

.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 [12]. Cellefinement: Stoe X-AREA [12]. Data reduction: Stoe X-RED [12].he structure was solved by direct-methods using SHELXS-97 [13]nd anisotropic displacement parameters were applied to non-ydrogen atoms in a full-matrix least-squares refinement basedn F2 using SHELXL-97 [13]. All carbon hydrogens except waterolecules were positioned geometrically and refined by a ridingodel with Uiso 1.2 times that of attached atoms and the remain-

ng H atoms (of water molecule) were located from the Fourierifference map. At this stage, the maximum difference densityf 1.57 eÅ−3 (the ratio of maximum/minimum residual density is.18) indicated the presence of a possible atom site. A check ofhe solvent-accessible volume showed a total potential volumef 204.8 Å3. Attempts to refine this peak as a water O atom (O7)esulted in a partial occupancy of 0.7. H atoms attached to O7 wereot located. Molecular drawings were obtained using ORTEP-III14].

. Results and discussion

.1. Determination of the crystal structure

An ORTEP-III [14] drawing of the structure is presented inig. 1 and selected bond distances and angles are listed in Table 2.ingle crystal X-ray structural analysis shows that copper(II)ompound consists of a neutral [Cu(enc)2(sac)2(H2O)] unit and.4 water molecules. The Cu(II) ion sits on a crystallographicwo-fold axis in a significantly square pyramidal environment

ith the � parameter of 0.32 (� = 0 for an ideal square pyramidal

eometry and � = 1 for an ideal trigonal pyramidal geometry)15], equatorially coordinated to the nitrogen atoms of thewo saccharinate moieties [Cu–Nsac = 2.023(2) Å] and the pyri-ine nitrogen atoms of the enc ligands [Cu–Nenc = 2.035(2) Å].

me. Displacement ellipsoids are drawn at the 40% probability level and H atoms are–� interactions, symmetry code (i) 1 − x, 1 − y, 1 − z).

I. Ucar et al. / Spectrochimica Acta Part A 72 (2009) 11–16 13

Table 2Interatomic bond distances (Å) and angles (◦) around the Co(II) ion and hydrogen bonding interactions in [Cu(enc)2(sac)2(H2O)]·1.4H2O.

(a) Bond lengths, bond angles

Bond lengths (Å)Cu1–N1: 2.023(2) Cu1–N2: 2.035(2) Cu1–O1: 2.230(4)N1–S1: 1.617(2) O5–S1: 1.428(2) O6–S1: 1.430(2)

Bond angles (◦)N1–Cu1–N2: 87.59(8) N1–Cu1–O1: 100.49(6) N2–Cu1–O1: 91.02(7)N2–Cu1–N2i: 177.95(14) N1–Cu1–N2i: 92.03(8) O5–S1–N1: 111.86(12)O6–S1–N1: 110.62(12) N1–C9–C10: 111.3(2) C9–N1–S1: 112.70(17)

(b) Hydrogen-bonding interactions (Å, ◦)D H· · ·A D—A H· · ·A D· · ·A D—H· · ·A

S

Tlcgaif[[[[tt[[ad[w[hg

t0da[sctS(S[[1iI

O1 H1A· · ·O7 0.845O1 H1A· · ·O6ii 0.845

ymmetry codes: (i) −x − 1, −y + 1; (ii) −x, −y + 2, z.

he five-fold coordination is completed with a aqua moleculeocated at the pyramid apex [Cu–Oaqua = 2.230(4) Å]. The Cu(II)ation departs from the mean plane defined by four nitro-en atoms of the pyramidal basis by 0.162(2) Å towards thexial aqua ligand. The Cu1–Nsac lengths in title complex aren good agreement with the corresponding distances reportedor [Cu(na)2(sac)2(H2O)]·(na: nicotinamide) [Cu–N: 1.998(2) Å]16], [Cu(py)3(sac)2]·(py: pyridine) [Cu–N: 2.038(2) Å] [17],Cu(bpy)2(sac)2(H2O)] (bpy: 2,4′bipyridine) [Cu–N: 1.999(3) Å]18], [Cu(sac)3(H2O)2]·ApyH (ApyH: 2-aminopyridinium)Cu–N: 2.011(2) Å] [19] and [Cu(nca)2(sac)2(H2O)]·(nca: nico-inic acid) [Cu–N: 2.044(7) Å] [20] but significantly shorterhan those found in [Cu(en)2(sac)2] (en: ethylenediamine)Cu N: 2.466(2) Å] [21], [Cu(ea)2(sac)2] (ea: ethanolamine)Cu N: 2.178 (2) Å] [22] and [Cu(ampy)2(sac)2] (ampy: 2-minomethylpyridine) [23] [Cu N: 2.662(2) Å]. The Cu–Oaqua

istance is similar to that found in [Cu(bpy)2(sac)2 (H2O)]

Cu–O: 2.272(4) Å] and [Cu(nca)2(sac)2(H2O)] [Cu O: 2.242(7) Å]hile that distance is slightly longer than that is found in

Cu(na)2(sac)2(H2O)] [Cu–O: 2.121(2) Å] due most probably to theydrogen bonding interactions between the aqua and acceptorroups.

cdaac

Fig. 2. Three dimensional structure of the title complex. Das

2.088 2.738 133.372.423 3.008 127.00

The molecular skeleton of the sac ions is nearly planar initle complex (rms deviation of atoms from the mean plane of.0174 Å). The N1–S1 [1.617(2) Å] and N1–C9 [1.369(3) Å] bondistances are close to those found in sodium saccharinate [24]nd in the related saccharinate complexes [20–23]. The C O1.224(3) Å] and S O [1.428(2) and 1.430(2) Å] distances in theulphonyl group within the saccharinate anion of the Cu(II)omplex are intermediate or very close to the corresponding dis-ances found in [Cu(py)2(sac)2(H2O)] [25] [C O = 1.228(3) Å;

O = 1.428(2) − 1.424(2) Å], [Cu(bpy)2(sac)](sac)·2H2Obpy: 2,2′-bipyridine) [26] [C O = 1.237(8) and 1.222(8) Å;

O = 1.436(2) Å, 1.443(5), 1.441(7) and 1.425(7) Å] andMn(phen)2(H2O)2](sac)·2H2O (phen: 1,10-phenanthroline)27] [C O = 1.253(5) and 1.246(6) Å; S O = 1.435(4), 1.436(4),.439(4) and 1.432(4) Å] as well as in [Co(Im)4(H2O)2]·(sac)2 [Im:midazole) [28] [C O = 1.237(2) Å; S O = 1.439(2)–1.445(2) Å].t does not seem that there is pronounced regularity in the

hange of the C O and S O bond lengths regarding the coor-ination of the deprotonated saccharin molecule to the centraltom or its participation in the hydrogen bonding. The bondngles of the metal-bonded saccharinato ligands as in the titleomplex are in good agreement with those of the metal-free

hed lines indicate the hydrogen bonding interactions.

14 I. Ucar et al. / Spectrochimica Acta Part A 72 (2009) 11–16

alline

ss(rf(i

tcsf

3

otrb(

tc

nbbpga(grwf

gtcghgt

TS

P

A

Fig. 3. EPR spectra of [Cu(enc)2(sac)2(H2O)]·1.4H2O (a) polycryst

accharinate ions in which the ring nitrogen is deprotonateduch as [Co(na)2(H2O)4]·(sac)2 (I) and [Ni(na)2(H2O)4]·(sac)2 (II)na: nicotinamide) [29], showing that the metal bonding to theing nitrogen exerts little effect on the molecular dimensions;or instance, the bond angle S–N–C = 112.7(2)◦ in title complexTable 2) and the corresponding angles of 111.5(2)◦ and 111.5(3)◦

n (I) and (II).Analysis of the crystal packing indicates that there are only one

ype of intermolecular hydrogen bond interactions (O–H· · ·O) in theomplex, involving the oxygen atoms of aqua ligand, saccharinateulphonyl oxygen and solvent water molecules (Fig. 2, see Table 2or details).

.2. Optical absorption and EPR studies

In the UV-range two strong absorption peaks werebserved at near 235 and 328 nm, which can be assignedo charge-transfer transition of the ligands. In the visibleange, one broad peak was observed near 754 nm, which can

e assigned to spin-allowed d–d transition bands of B2 → B1dxy → dx2−y2 ).

The EPR spectra of the title complex recorded in the polycrys-alline state at room temperature provide information about theoordination environment around the copper(II) ion. Five coordi-

eCtl

able 3pin Hamiltonian and bonding parameters of copper(II) complexes.

[Cu(enc)2(sac)2(H2O)]·1.44H2O [Cu(L)py

olycrystalline (298 K)g‖ 2.389 2.163g⊥ 2.057 2.076A‖ 165 –˛2 0.9078 –ˇ2 0.9687 –�2 0.7259 –K‖ 0.8794 –K⊥ 0.6591 –G 6.800 2.140

g‖ 2.296 2.212g⊥ 2.060 2.066A‖ 150 197˛2 0.7716 0.814ˇ2 0.993 0.896�2 0.877 0.968K‖ 0.766 0.733K⊥ 0.677 0.789

values in 10−4 cm−1. L: 2-hydroxyacetophenone-N(4)-phenyl semicarbazone, L′: 2-hydro

at 298 K (b) in DMF at 110 K together with the simulation curve.

ated copper(II) complex may possess two geometries, i.e. trigonalipyramidal and square pyramidal [15], which are characterizedy ground states dx2−y2 or dz2 , respectively [30]. The EPR spectrarovide an excellent basis for distinguishing between these tworound states. The polycrystalline EPR spectra of copper(II) complext 298 K showed axial spectra with well-defined g‖(2.389) and g⊥2.057) features (Fig. 3a; Table 3) together with hyperfine lines. The‖ > g⊥ value suggest a distorted square pyramidal structure andules out the possibility of a trigonal bipyramidal structure whichould be expected to have g⊥ > g‖, according the results obtained

rom the XRD data (� = 0.32).For magnetically nondilute Cu(II) complexes showing resolved

‖ and g⊥ features, the G[= (g‖ − 2)/(g⊥ − 2)] value may be usedo estimate exchange coupling [31]. For 3.0 < G < 5.0, the exchangeoupling is considered to be weak and in such cases the observed-values may reflect the local Cu(II) environment. On the otherand, G < 3.0 indicates strong exchange coupling and the observed-values do not reflect the individual Cu(II) molecular geome-ry.

The G-value, 6.80, for the title complex indicates weakxchange interaction between the adjacent Cu(II) centers [Cu1, . . .,u1* = 9.016(1) Å; symmetry code *: −y + 1, −x + 1/2, z − 1/4]. Hence,he observed g and hyperfine values can be considered to reflect theocal Cu(II) molecular geometry.

] [41] [Cu(HL)]·Cl [39] [CuL′(phen) [40]

2.236 g1 = 2.0382.098 g2 = 2.056– g3 = 2.192– –– –– –– –– –2.400 –

DMF(77 K)2.200 2.1922.057 2.050

174 176.17 0.8005 0.73650 0.8571 0.86877 0.8993 0.94090 0.6865 0.63982 0.7199 0.6871

xyacetophenone N(4)-thiosemicarbzones, py: pyridine, phen: 1,10-phenenthroline.

I. Ucar et al. / Spectrochimica Act

Table 4Assignment of some characteristic IR bands of [Cu(enc)2(sac)2(H2O)]·1.4H2O, com-pared with those of sodium saccharinate hydrate (band positions in cm−1).

Assignment (cm−1) Na(sac)·H2O[24] [Co(enc)2(sac)2(H2O)]·1.4H2O

�(OH) 3333 s,br; 3264 s 3615, 3534, 3424 s,br�(CH) 3080 vw, 3050 w, 3012 vw 3115, 2861 vw�(CH)py – 2983 vw�(CO)ein. – 1720 vs�(CO)sac 1642 vs; 1629 sh 1658 vs�(CN)py – 1583 s; 1428 w�(CC) 1590 s; 1555 vw; 1460 m 1455 w�s(CNS) 1336 m 1367 m�as(SO2) 1258 vs 1292 vs;�(CH) 1165 sh; 1118 s; 1051 m 1054 m�s(SO2) 1150 vs; 1157 vsRing breathing – 1012 m�as(CNS) 950 m 958 mo.p. ring def py – 748 m�(CO) 794 w 674 m�(CCC)py – 644 vw�(SO2) 610 m 597 m�

pos

((ft

tatrm

˛

b

wtw

0bK�wc

3

wtv�tTa

iRib[luo[tthncosrt�m

3

[Zsr+[cc

Dneldraaper

4

nsb

patfa

p

(CNS) 543 w 543 m

y, pyridine; sac, saccharinate; enc, ethylnicotinate; 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.

In the EPR spectrum of the copper(II) complex in frozen DMF110 K), the expected superhyperfine lines of three nitrogen atomstwo dpa and one dpc nitrogen) are not observed but it showsour clearly resolved hyperfine lines (65Cu, I = 3/2) correspondingo MI = −3/2, −1/2, 1/2, 3/2 transitions (�Ms = ±1) (Fig. 3b).

The EPR parameters g‖, g⊥, A‖ [Cu(II)] and the energies of d–dransitions were used to evaluate the bonding parameters �2, �2

nd �2, which may be regarded as measures of the covalency inhe in-pane �-bonds, in-plane �-bonds and out-of-plane �-bonds,espectively. The value of in-plane �-bonding parameter �2 is esti-ated from the expression [32]

2 = − A‖0.036

+ (g‖ − 2.00277) + 37

(g⊥ − 2.00277) + 0.04

The following simplified parameters were used to calculate theonding parameters [33],

K2‖ (g‖ − 2.00277)

Ed–d

8�0

K2⊥ = (g⊥ − 2.00277)

Ed–d

2�0

here K‖ = ˛2ˇ2 and K⊥ = ˛2�2, K‖ vs. K⊥ are orbital reduction fac-ors and �0 represents the one electron spin orbit coupling constanthich equals to −828 cm−1.

According to Hathaway [34], for pure �-bonding K‖ ≈ K⊥ ≈.77, for in-plane �-bonding K‖ < K⊥, whereas for out-of-plane �-onding K‖ > K⊥. In title copper(II) complex, it is observed that‖ > K⊥ and this indicates the presence of significant out-of-plane-bonding. In-plane �-bonding is significantly covalent characterhile in-plane and out-of-plane �-bonding is significantly ionic

haracter (Table 3).

.3. FT-IR investigation

IR data for the title complex is shown in Table 4 and comparedith those of sodium saccharinate monohydrate [24]. The absorp-

ion bands between 3600 and 3400 cm−1 are characteristic of �(OH)

ibrations of aqua and crystal water molecules. The existence of(OH) bands around 3500 cm−1 might be taken as an indication ofhat some of the aqua OH groups are very weakly hydrogen bonded.he relatively weak absorption bands between 3110 and 2861 cm−1

re assigned to the �(CH) vibrations. The bands due to the stretch-

tocic

a Part A 72 (2009) 11–16 15

ng of the C O group of ein ligands were found at 1720 cm−1.egarding the vibration modes of saccharinate, the �(C O) stretch-

ng vibration is observed at 1658 cm−1 as a very strong absorptionand and appears at significantly higher frequency compared toCu(sac)2(H2O)4]·H2O (1610 cm−1), in spite of the fact that the sacigands in title complex are N-bonded. Due to intra-and intermolec-lar interactions such as hydrogen bonds, the �(C O) frequencyften does not correlate to the coordination mode of the ligand35]. The absorption bands around 1583 and 1425 cm−1 correspondo the �(C N) and �(C C) vibrations of the aromatic rings, respec-ively. Although the CN and NS stretching of the saccharinate anionave often been analyzed separately [36], the delocalization of theegative charge over the anion affects the bonds, which thereforean be analyzed as a definite entity, the CNS moiety. The assignmentf the IR bands at 1326 and 950 cm−1 to the symmetric and anti-ymmetric stretching of this unit, respectively, is supported by theirelative intensities, as well as by comparisons to equivalent vibra-ions in phthalimide and related molecules [37]. The �as(SO2) ands(SO2) vibration bands appear as a very strong bands at approxi-ately 1292 and 1153 cm−1, respectively.

.4. Cyclic voltammetry

The electrochemical behavior of the sodium saccharinate andM(II)(sac)2(H2O)4]. 2H2O complexes [M(II) = Fe, Co, Ni, Cu andn] was investigated by cyclic voltammetry in dimethylformamideolutions using a glassy carbon electrode [38]. The sodium saccha-inate is electrochemically inactive in the potential range between1.1 and −1.9 V vs. NHE (normal or standard hydrogen electrode)38] while the metal–saccharinate complexes exhibit both metalentered quasi-reversible redox couple and decomposition of theomplex associated with the loss of the ligand.

The voltammetric behavior of title complex is investigated inMF (dimethylformamide) solution by cyclic voltammetry using-Bu4NClO4 as supporting electrolyte. The cyclic voltammogramxhibits only one metal centered quasi-reversible redox couple,ocated at E1

1/2 = 0.45 V vs. Ag/AgCl reference electrode. No evi-ences of saccharinate and ethylnicotinate ligand oxidation oreduction in the selected potential range (from −1.00 to 1.00 V)re observed. The ratio of peak current (Ipc/Ipa) is not equal to 1nd �Ep (=|Epa − Epc|) value is ≥60 mV. Therefore, the redox cou-le in voltammetric data can be attributed to a quasi-reversible 1− transfer process. The Ip/�1/2 value is almost constant for all scanates. This establishes the electrode process as diffusion controlled.

. Conclusion

Mononuclear copper(II) complex of saccharin with ethynicoti-ate [Cu(enc)2(sac)2(H2O)]·1.4H2O has been synthesized and itstructural, EPR, spectroscopic and voltammetric properties haveeen studied.

X-ray diffraction analysis of the complex have shown that cop-er(II) compound consists of a neutral [Cu(enc)2(sac)2(H2O)] unitnd 1.4 water molecules. The Cu(II) ion sits on a crystallographicwo-fold axis in a significantly square pyramidal environmentormed by two sac and two enc ligands together with an aqua ligandt the pyramid apex position.

The polycrystalline EPR study of the title complex at room tem-erature have indicated that the coordination environment around

he copper(II) ion is a distorted square pyramidal structure bybserving the g‖ > g⊥ value. The exchange coupling value of theomplex is estimated as 6.80 explaining that the title complexndicates weak exchange interaction between the adjacent Cu(II)enters. The EPR parameters together with d–d transitions ener-

1 ica Act

gp

mo

S

tCCofh

R

[[

[

[[

[

[

[

[[[

[[[[[

[[[[[[

[[

[

[[

6 I. Ucar et al. / Spectrochim

ies were used to evaluate the bonding parameters and found theresence of significant out-of-plane �-bonding in the complex.

The cyclic voltammogram of the complex has exhibited only oneetal centered quasi-reversible redox couple but no evidences of

xidation or reduction of saccharinate and ethylnicotinate ligands.

upplementary data

Crystallographic data (excluding structure factors) for the struc-ure in this paper have been deposited with the Cambridgerystallographic Data Centre as the supplementary publication no.CDC 648136. 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 web:ttp://www.ccdc.cam.ac.uk.

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