ISSN 1070-3284, Russian Journal of Coordination Chemistry, 2006, Vol. 32, No. 3, pp. 231. © Pleiades Publishing, Inc., 2006. Original Russian Text © V. I. Murav’ev, 2006, published in Koordinatsionnaya Khimiya, 2006, Vol. 32, No. 3, pp. 240. LETTER TO THE EDITOR Interpretation of the EPR Spectral Parameters for Coordination Compounds V. I. Murav’ev Izmeritel' Research and Production Center, Ulyanovsk, Russia Received July 1, 2005 DOI: 10.1134/S1070328406030110 exp Analysis of the experimental parameters of the EPR and g > 2.0023) caused by the effect of CTS in the || spectra, in particular, those of transition metal ions, molybdenum(V) oxyhalide complexes (4d ) . The shows that interpretation of the EPR parameters exp requires, in some cases, data on the electron distribu- anomalous values g > 2.0023 for the low-spin chro- tion not only in the antibonding but also in the bonding mium(I) nitrosyl complexes (3d ) have also been states of the paramagnetic complex. These data are explained in terms of this method. The SP and vibronic needed for interpretation in those cases where the spec- coupling effects on the isotropic parts of the A-tensor components, inducing an anomalous behavior of these tral parameters exhibit anomalous behavior related to spectral parameters in tetragonal square planar Cu(II) the inﬂuence of either “charge transfer” states (CTS) or complexes (3d ) have been considered . The anoma- spin polarization (SP). Quantum chemical calculation lous behavior of the HFC and the LHFC in lead(III) of the EPR parameters is used traditionally to interpret cubic complexes (6s ) has been investigated using the the spectra. However, the semiempirical versions of spectroscopic method . quantum chemical calculations used most often  are usually unable to reproduce the whole set of the Apart from interpretation of EPR spectral parame- observed EPR spectral parameters due to the approxi- ters, the use of the covalency parameters according to their plain chemical meaning may provide conclusions mations applied . concerning the electronic structures of coordination An alternative method suitable for direct interpreta- compounds on the basis of EPR data . The utility of tion of the magnetic resonance parameters without EPR-derived information on the electron distribution in intermediate quantum chemical calculations has been the bonding states of paramagnetic complexes is obvi- proposed . This approach is based on the inverse ous. problem of EPR spectroscopy, i.e., calculation of the covalent bond parameters (covalency parameters) of REFERENCES the antibonding and bonding states from the experi- mental EPR spectra and optical spectroscopy of com- 1. Yunusov, P.B., Murav’ev, V.I., and Shatrukov, L.F., Pro- gramma dlya rascheta elektronnoi struktury komple- plexes. The covalency parameters obtained in this way ksnykh soedinenii (Program for the Calculation of the are further used to calculate the contributions of differ- Electroic Structure of Complex Compounds), Moscow: ent chemical nature to the components of the Zeeman VINITI, 1975. interaction tensor (g-tensor), hyperﬁne coupling (HFC) 2. Murav’ev, V.I., Ovchinnikov, I.V., and Yunusov, N.B., tensor (A-tensor), and the ligand HFC (LHFC) tensor Izv. Akad. Nauk SSSR, Ser. Khim., 1974, no. 7, p. 1609. (A -tensor). Thus, the covalency parameters function as 3. Murav’ev, V.I., Koord. Khim., 1989, vol. 15, no. 10, the ﬁtting parameters for the microscopic model of the p. 1314. complex; they are optimal when the parameters of the 4. Murav’ev, V.I., Koord. Khim., 2004, vol. 30, no. 2, p. 87. experimental EPR spectra are reproduced. Such (spec- troscopic) method does not involve any quantum chem- 5. Murav’ev, V.I., Koord. Khim., 2005, vol. 31, no. 5, p. 1. ical approximations and allows one to interpret the g-, 6. Murav’ev, V.I., Koord. Khim., 2005, vol. 31, no. 3, A-, and A -tensor components within the framework of p. 204. a single model. 7. Murav’ev, V.I., Fizika Tverd. Tela, 2004, vol. 46, no. 5, p. 830. The spectroscopic method is used to interpret the 8. Murav’ev, V.I., Koord. Khim., 2005, vol. 31, no. 9, exp exp anomalous values of g-tensor components ( g > g , || ⊥ p. 643.
Russian Journal of Coordination Chemistry – Springer Journals
Published: Mar 20, 2006
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