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4913110 
Journal Article 
Effect of substituents, solute-solute-non-polar solvent interactions and temperature on the spectral properties of bis(dithiophosphato)copper(II) complexes 
Yordanov, ND; Ranguelova, K; Gadjanova, I 
2002 
1 
Transition Metal Chemistry
ISSN: 0340-4285 
KLUWER ACADEMIC PUBL 
DORDRECHT 
27 
5 
490-496 
English 
WOS:000175796000006 
Extended studies by e.p.r. and electronic spectroscopy on the effect of different non-polar solvents, temperature and disulfide concentration on the spectral properties of bis(dithiophosphato)copper(II), Cu[(RO)(2)PS2](2), complexes [R = Me, Et and i-Pr] are reported. The molar absorptivity and e.p.r. intensity are very sensitive to the shape and size of the remote ligand substituents and increase in the order: Me < Et < i-Pr. The nature of the solvent and time after dissolution are also important regarding the magnitude of the e.p.r. intensity and molar absorptivity which, 1 h after dissolution, do not follow Beer's law. The molar absorptivities obtained at a given (CuI)-I-I(R-2-dtp)(2) concentration increase in the solvent order: n-hexane < n-heptane < CCl4 < PhMe < PhH < CHCl3. Twenty-four hours after dissolution the same samples exhibit: (i) linearity between absorbance and concentration of (CuI)-I-I(R-2-dtp)(2); (ii) a significant increase in molar absorptivity which is not equal for all the complexes studied and follows the same substituent and solvent orders. Beer's law is satisfied above 5 x 10(-4) M for [(RO)(2)PS2](2)Cu (R = Et, i-Pr) and above 3 x 10(-)3 M for [(MeO)(2)PS2]Cu. A significant additional increase, ca. 30-40%, of molar absorptivity, is obtained by increasing the solution temperature from 20 to 50 degreesC. The molar absorbtivity remains unchanged during 2-3 days after reducing the temperature. Further increase of molecular absorbtivity appears after addition of the corresponding disulfide of dithiophosphate [(RO2)PS2-S2P(RO)(2)] to (CuI)-I-I[(RO)(2)PS2](2). The molar absorptivity of Cu[(i-PrO)(2)PS2](2) increases from 4.8 x 10(3) cm(-1) M-1, 1 h after dissolving the complex up to 2 x 10(4) cm(-1) M-1 after addition of the corresponding disulfide. The observed effects are explained on the basis of a self-redox reaction taking place in this type of sulfur containing copper(II) complexes.