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Gancheva V, Yordanov ND, Koev L: EPR and electronic spectral properties of aryl-substituted bis (dithiophosphato) copper (II) complexes. Spectrochim Acta A Mol Biomol Spectrosc. 2008 May;69(5):1317-21. Epub 2007 Oct 2.
The spectral properties of bis (diaryl-dithiophosphato) copper (II) complexes, [Cu (S (2) P (OR)(2))(2)], with R = o-cresyl (complex I) and 2,6-dimethylphenyl (complex II) are studied by EPR- and vis spectroscopy. In solid (powder) state both complexes exhibit dark brown colour and are paramagnetic. Room temperature EPR spectra of the complexes dissolved in non-coordinating (C (6) H (5) CH (3), C (5) H (12), C (6) H (14)), acceptor (CHCl (3), CCl (4)) or donor (DMFA, DMSO) solvents have typical features of the chromophore CuS (4). In non-coordinating and acceptor solvents their isotropic EPR parameters are: g (iso)=2.047+/-0.003, (Cu) A (iso) = 7.2+/-0.1 mT and (P) A = 0.95+/-0.1 mT. An absorption band characterizes the vis spectra in these solvents with a maximum at 427 nm, due to a ligand-to-metal charge-transfer transition. One hour after dissolution the absorbance at 427 nm follows Beer's law with molar absorptivity (epsilon) about 11000, which does not change significantly after 24 h staying at room temperature or after 30 min heating at 50 degrees C. Both DMFA and DMSO exhibit specific solute-solvent interaction with the acceptor centre of copper complex yielding an axial adduct, with increased g-factor and decreased (hf) A compared to the initial complex. An additional EPR signal with unresolved hyperfine structure is also detected in DMSO. EPR and vis intensities of both bis (diaryl-dtp) Cu (II) complexes decrease after dissolution in both solvents. Moreover, they are EPR silent in pyridine and do not show any absorption in the vis spectra. |
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