Planar copper and nickel triangles with a guanidine-derived ligand

Abstract

A novel guanidine-derived ligand with three tetradentate N₄ coordination sites and its trinuclear copper and nickel complexes, [Cu₃] and [Ni₃], were synthesized. X-ray structural analyses of [Cu₃] and [Ni₃] reveal the complexes to have planar triangular structures with pseudo C₃ symmetry. Magnetic measurements for [Cu₃] and [Ni₃] complexes indicate that antiferromagnetic interactions are operative in both complexes with intratriangle exchange coupling constants of g = 2.08(1), J = −130(1) cm⁻¹ for [Cu₃], and g = 2.18(1), J = −14.9(1) cm⁻¹ for [Ni₃]. [Cu₃] has a doublet spin ground state at low temperature, while the magnetic susceptibility data and magnetization curve suggest that the ground state of [Ni₃] is spin singlet.