ESR study of copper diethyldithiophosphate

Abstract

ESR investigations are reported in single crystals of copper diethyldithiophosphate, magnetically diluted with the corresponding diamagnetic nickel complex. The spectrum at normal gain shows hyperfine components from ⁶³Cu, ⁶⁵Cu, and ³¹P nuclei. At much higher gain, hyperfine interaction from ³³S nuclei in the ligand is detected. The spin Hamiltonian parameters relating to copper show tetragonal symmetry. The measured parameters are g_∥=2.085, g_⊥=2.025, A⁶³Cu=149.6×10^-4 cm^-1, A⁶⁵Cu=160.8×10^-4 cm^-1, B^Cu=32.5×10^-4 cm^-1 and Q^Cu ∞ 5.5×10^-4 cm^-1. The ³¹P interaction is isotropic with a coupling constant A^P=9.6 ×10^-4 cm^-1. Angular variation of the ³³S lines shows two different hyperfine tensors indicating the presence of two chemically inequivalent Cu S bonds. The experimentally determined hyperfine constants are A₁^s=34.9×10^-4 cm^-1, B₁^s=26.1×10^-4 cm^-1, A₂^s=60.4×10^-4 cm^-1, B₂^s=55.5×10^-4 cm^-1. The hyperfine parameters show that the hybridization of the ligand orbitals is very sensitive to the symmetry around the ligand. The g values and Cu hyperfine parameters are not much affected by the distortions occurring in the ligand. The energies of the d-d transitions are determined by optical absorption measurements on Cu diethyldithiophosphate in solution. Using the spin Hamiltonian parameters together with optical absorption results, the MO parameters for the complex are calculated. It is found that in addition to the σ bond, the Π bonds are also strongly covalent.