Electronic Structure and Nature of the Ground State of the Mixed-Valence Binuclear Tetra (mu-1,8-naphthyridine-N,N')-bis(halogenonickel) Tetraphenylborate Complexes: Experiental and DFT Characterization

摘要

The ground state electronic structure of the mixed-valence systems [Ni_2(napy)_4X_2](BPh_4) (napy = 1,8-naphthyridine; X = Cl, Br, I) was studied with combined experimental (X-ray diffraction, temperature dependence of the magnetic susceptibility, and high-field EPR spectroscopy) and theoretical (DFT) methods. The zero-field splitting (zfs) grouns S = 3/2 spin state is axial with |D| approx 3 cm~(-1). The iodide derivative was found to be isostructural with the previously reported bromide complex, but not isomorphous. The compound crystallizes in the monoclinic system, space group P2_1, with a = 17.240(5), b = 26.200(5), c = 11.340 (5), beta = 101.320(5)°. DFT calculations were performed on the S = 3.2 state to characterize the ground state potential energy surface as a function of the nuclear displacements. The molecules can thus be calssified as Class III mixed-valence compounds with a computed delocalization parameter, B = 3716, 3583, and 3261 cm~(-1) for the Cl, Br, and I derivatives, respectively.