title: EPR and electronic spectral properties of aryl-substituted bis(dithiophosphato)copper(II) complexes.
abstract: 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.
authors.affiliation: Laboratory EPR, Institute of Catalysis, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria.
authors.forename: Veselka
authors.initials: V
authors.lastname: Gancheva
authors.forename: Nicola D
authors.initials: ND
authors.lastname: Yordanov
authors.forename: Lachezar
authors.initials: L
authors.lastname: Koev
mesh_terms: D000042:Absorption; D003300:Copper / Q000737:chemistry*; D004121:Dimethyl Sulfoxide / Q000737:chemistry; D004126:Dimethylformamide / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D010710:Phosphates / Q000737:chemistry*; D012996:Solutions; D012997:Solvents; D013696:Temperature; D013997:Time Factors; D014050:Toluene
chemical_list: D010710:Phosphates; D012996:Solutions; D012997:Solvents; D014050:Toluene; D003300:Copper; D004126:Dimethylformamide; D004121:Dimethyl Sulfoxide