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)Å, 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 L^2–. 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 µ_B at room temperature but converges to 1.80 ± 0.01 µ_B at 170 K. The exchange integral J, based on the isotropic exchange model ℋ=–2∑j_ijŜ_iŜ_j, is –290.8 cm^–1.