title: EPR and ESE of CuS4 complex in Cu(dmit)2: g-factor and hyperfine splitting correlation in tetrahedral Cu-sulfur complexes.
abstract: Pseudotetrahedral CuS4 complexes of Cu(dmit)2 compound in DMF solution were studied by EPR, UV-Vis and electron spin echo methods. After rapid freezing at 77 K a good glassy state is formed and the CuS4 complex has a D(2d) symmetry of a compressed tetrahedron with xy ground state and spin-Hamiltonian parameters g||=2.089, g⊥=2.026, A||=146×10(-4) cm(-1) and A⊥=30×10(-4) cm(-1). The complex is not deformed in the glassy state and is very rigid as indicated by the echo detected spectrum and by electron spin relaxation which is governed by reorientations of methyl groups of surrounding DMF molecules as shown by electron spin echo envelope modulation (ESEEM) spectrum. The g|| and A|| of Cu(dmit)2 and other CuS4 complexes collected in Peisach-Blumberg correlation diagram were analyzed using extended Molecular Orbital theory. We explain why the correlation line for copper-sulfur complexes has larger slope compared to the CuO4 and CuN4 tetrahedra. Along the correlation line the delocalization of unpaired electron density onto ligand is constant and varies from β=0.78-0.83 for g|| in the range 2.06-2.10 of correlation diagram. The slope of the line is determined by the product of MO-coefficients αc1, where α is a parameter characterizing delocalization of unpaired electron in x(2)-y(2) and c1<1 is a mixing parameter decreasing when 4p contribution grows. We found, unexpectedly, that αc1≈0.7 for all CuS4 complexes suggesting a correlation between degree of tetrahedral deformation and MO-parameters. MO-coefficients for Cu(dmit)2 are α=0.753, β=0.752 and c1=0.930 confirming a strong delocalization of unpaired electron in xy and x(2)-y(2) orbitals.
authors.affiliation: Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznan, Poland. Electronic address: skh@ifmpan.poznan.pl.
authors.forename: Stanisław K
authors.initials: SK
authors.lastname: Hoffmann
authors.forename: Janina
authors.initials: J
authors.lastname: Goslar
authors.forename: Stefan
authors.initials: S
authors.lastname: Lijewski
authors.forename: Alina
authors.initials: A
authors.lastname: Zalewska
keywords: Correlation diagram A(||) vs. g(||); Electron paramagnetic resonance; Electron spin echo; Molecular orbital theory of CuS(4); Tetrahedral CuS(4) complexes