Theoretical studies of electronic structures, magnetic properties and electron conductivities of one-dimensional Nin (n = 3, 5, 7) complexes

Abstract

Electronic structures, magnetic properties and electron conductivities of linearly aligned one-dimensional (1-D) Ni(II)₃, Ni(II)₅ and Ni(II)₇ complexes, i.e. [Ni₃(dpa)₄NCS₂], [Ni₅(tpda)₄X₂] (X = Cl, CN, N₃, NCS) and [Ni₇(teptra)₄Cl₂], are systematically investigated by the broken-symmetry B3LYP calculations and simulations based on an elastic scattering Green's function theory. Calculated spin densities appear only at terminal Ni ions, while inner Ni ions are the closed-shell. The calculated effective exchange integrals (J_ab) values reproduce well the experimental results that indicate anti-ferromagnetic (AF) interactions between two terminal Ni ions. Natural orbitals and their occupation numbers show that a change in the weak AF couplings by axial ligands in penta-nickel complexes originates in σ-type orbitals. Simulated electron conductivities of [Ni₃(dpa)₄NCS₂] and [Ni₅(tpda)₄NCS₂] semi-quantitatively correspond to the experimental results. By the analyses, it is elucidated that electrons are mainly transmitted by σ-type orbitals, but the bonds between Au and axial ligands are also dominant factors for conductivity.