Synthesis, X‐ray Studies and Magnetic Properties of Dinuclear NiII and CuII Complexes Bridged by the Azo‐2,2′‐bipyridine Ligand

Abstract

AbstractTwo new paramagnetic transition metal complexes that contain the bridging ligand azo‐2,2′‐bipyridine (abpy) have been prepared and characterized by X‐ray crystallography and magnetic susceptibility measurements. The compound [Ni2(μ‐abpy)(CH3CN)2(NO3)4]·2CH3CN (1·2CH3CN) crystallizes in the triclinic space group P$\bar 1$ with a = 8.290(5) Å, b = 8.343(5) Å, c = 11.180(5) Å, α = 105.36(3)°, β = 94.39(3)°, γ = 107.56(3)°, V = 700.5(7) Å3 and Z = 1. The related salt [Cu2(μ‐abpy)(CH3CN)8][BF4]4 (2) crystallizes in the triclinic space group P$\bar 1$ with a = 10.240(2) Å, b = 10.597(2) Å, c = 10.712(2) Å, α = 64.23(3)°, β = 78.21(3)°, γ = 78.57(3)°, V = 1026.7(3) Å3 and Z = 1. Solutions of 2 eventually produce the polymeric CuI compound {[Cu(μ‐abpy)][BF4]}∞ (3) which was also crystallographically characterized: monoclinic space group P21/n, with a = 9.295(2) Å, b = 9.541(2) Å, c = 13.486(3) Å, β = 91.58(3)°, V = 1195.5(4) Å3 and Z = 4. The magnetic properties of these dinuclear paramagnetic complexes have been studied in detail, and have provided an opportunity for probing the ability of this ligand to mediate magnetic exchange interactions between paramagnetic metal centers. Compound 1 exhibits antiferromagnetic exchange interactions (J = −7.5 cm−1) whereas the magnetic interactions in compound 2 were found to be negligible. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)