466
L.K. Gupta et al. / Spectrochimica Acta Part A 65 (2006) 463–466
Table 3
EPR spectral data of the complexes
Complex
Data as polycrystalline sample
Data in DMSO solution
g
g
giso
G
g
g
⊥
giso
G
||
⊥
||
[Cu(L)Cl]
[Cu(L)Br]
[Cu(L)NO3]
[Cu(L)CH3COO]
[Cu(L)ClO4]
2.2451
2.1978
2.1857
2.2158
2.0987
2.0640
2.0808
2.1093
2.0318
2.1475
2.1086
2.1158
2.1448
2.0541
2.4833
3.0906
2.2983
1.9744
3.1006
2.1546
2.0035
2.4580
2.1980
2.1416
2.0847
2.0148
2.6739
2.2899
2.0472
2.1080
2.0110
2.6019
2.2593
2.0787
1.8253
0.2365
0.6796
0.6830
3.0000
ground state [18]. In tetrahedral geometry the unpaired elec-
[2] N.P. Du-Hoi, N.D. Xuong, N.H. Ham, F. Binon, R. Roger, J. Chem. Soc.
(1953) 1358;
2
tron lies in the dx2−y2 orbital giving B1g as the ground state
M. Fabin, G. Palmer, Biochemistry 40 (2001) 40.
with g > g . The g and g values were computed from the
||
⊥
||
⊥
[3] T.S. Ma, T.M. Tian, Antibiot. Chemother. 3 (1953) 491;
I. Pozdnyakova, P.W. Stafshede, Biochemistry 40 (2001) 13728.
[4] Q. Albert, Nature 9 (1953) 370;
U. Kuehn, S. Warzeska, H. Pritzkow, R. Kraemer, J. Am. Chem. Soc. 123
(2001) 6125.
[5] J.M. Price, Fed. Proc. 20 (1961) 223;
spectrum using DPPH free radical as ‘g’ marker [19]. The trend
g > g > ge (2.0023) observed for these complexes, in poly-
||
⊥
crystalline samples only, indicates that the unpaired electron is
localized in dx2−y2 orbital of the Cu(II) ions and the spectral fea-
tures are characteristics of axial symmetry [20] and tetrahedral
geometry. This trend (g > g > ge) was not observed in the EPR
K.D. Karlin, J. Zubieta, Copper Coordination Chemistry: Biochemistry
Chemical and Inorganic Perspectives, Adenine Press Guilderland, New
York, 1983.
||
⊥
spectra recorded in DMSO solution, further support for the six
coordinated geometry in the solution phase.
[6] A.G. Mauk, R.A. Scott, H.B. Gray, J. Am. Chem. Soc. 102 (1980) 4360.
[7] W.J. Geary, Coordin. Chem. Rev. 7 (1971) 81.
[8] P.S. Kalsi, Spectroscopy ofOrganicCompounds, fourth ed., New Age Inter-
national (P) Ltd. Publisher, New Delhi, 2001;
In addition there is exchange-coupling interaction between
two copper centers explained by Hathaway [14] expression
g = (g − 2)/(g − 2). According to Hathaway if the value of
||
⊥
G.C. Silverstein, T.C. Morril, Bassler, Spectrophotometric Identification
of Organic Compounds, third ed., John Wiley and Sons Inc., New York,
1974;
G is greater than four, the exchange interaction is negligible,
whereas when the value of G is less than four a considerable
interaction is indicated in solid complex. The calculated G val-
ues follow the order: Cl− ≈ Br− > NO3− > CH3COO−. These
indicate the lower G value of the acetate complexes and hence
larger exchange interaction than the nitrate and chloride com-
plexes.
J.R. Dyer, Applications of Absorption Spectroscopy of Organic Com-
pounds, Prentice Hall, Eagle-wood Cliffs, New Jersy, 1965.
[9] S. Chandra, K.K. Sharma, Acta Chim. Acad. Sci. Hunga. 111 (1982) 5.
[10] S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 1563.
[11] K. Nakamoto, Infrared and Raman Spectra of Inorganic and Coordination
Compounds, third ed., Wiley Interscience, New York, 1978.
[12] S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 2411.
[13] S. Chandra, K.B. Pandya, S.K. Sindhwani, R.P. Singh, Gazz. Chim. Ital.
110 (1980) 207.
Acknowledgements
[14] A.A.G. Tomilson, B.J. Hathaway, D.E. Willing, P.J. Nicholls, J. inorg. Nucl.
Chem. 39 (1977) 417.
[15] S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 1751.
[16] A.B.P. Lever, Inorganic Electronic Spectroscopy, Elsevier, Amsterdam,
1984.
The authors are thankful to the Department of science and
Technology and Defence Research and Development Organiza-
tion for financial assistance. We also express our sincere thanks
to RSIC, IIT Mumbai for recording EPR spectra and ACBR,
Delhi University, for recording IR spectra.
[17] A.B.P. Lever, Crystal Field Spectra. Inorganic Electronic Spectroscopy,
first ed., Elsevier, Amsterdam, 1968, pp. 249–360.
[18] S. Chandra, L.K. Gupta, Spectrochim. Acta A 60 (2004) 3079;
S. Chandra, L.K. Gupta, Spectrochim. Acta A 62 (2006) 307.
[19] S. Chandra, L.K. Gupta, Spectrochim. Acta A 61 (2005) 2139.
[20] S. Chandra, L.K. Gupta, Spectrochim. Acta A 61 (2005) 2549;
S. Chandra, L.K. Gupta, Sangetika Spectrochim. Acta A 62 (2006) 453.
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