Synthesis, structure, and magnetism of the trinuclear copper(II) complex [Cu(CuL)2][ClO4]2[H2L = 3,3′-(trimethylenedinitrilo)bis(2-butanone oxime)

Abstract

The trinuclear copper(II) complex [Cu(CuL)2][ClO4]2[H2L = 3,3′-(trimethylenedinitrilo)bis-(2-butanone oxime)] has been synthesized. It crystallizes in monoclinic space group C2/c, with Z= 4, a= 14.253(1), b= 18.798(2), c= 12.675(1)A, and β= 106.92(1)°. The structure consists of trinuclear cations [Cu(CuL)2]2+ and perchlorate ions. The central copper is co-ordinated by oximate oxygens of two CuL entities and the configuration around the metal is significantly distorted from tetrahedral with a dihedral angle of 33.31 (6)°. Each terminal copper adopts an essentially planar configuration with the nitrogen atoms of L2–. The three chromophores in the cation are bent at the edges of the bridging oximate oxygens, with a dihedral angle of 55.88(9)°, to afford a butterfly shape for the cation. In the crystal the trinuclear cations interact with each other at the terminal copper, in the so-called out-of-plane mode, through oximate oxygen to form an infinite chain along the c axis. Cryomagnetic investigations in the range 80–300 K revealed a strong antiferromagnetic spin-exchange interaction within the molecule; the magnetic moment per cation is 2.00 µB at room temperature but converges to 1.80 ± 0.01 µB at 170 K. The exchange integral J, based on the isotropic exchange model ℋ=–2∑jijŜiŜj, is –290.8 cm–1.