Structure and magnetic properties of a syn-anti carboxylate bridged linear trinuclear copper(II) complex with ferromagnetic exchange interaction

Abstract

The synthesis, crystal structure and magnetic properties are reported for the trinuclear compound [Cu(H 2O) 4{Cu(HL)(H 2O)(ClO 4)} 2][ClO 4] 2·2H 2O, where HL is the monodeprotonated form of 6-methylamino-1,3-dimethyl-5-[(2′-carboxyphenyl)azo]uracil. The compound crystallizes in the triclinic system, space0 group P 1 , with cell constants a=7.824(3), b=12.278(3), c=13.705(9) Å, α=104.34(3), β=91.80(3), γ=103.37(5)° and Z=1. The structure was solved and refined to R=0.071 ( R w=0.064). The structure consists of trinuclear [Cu(H 2O) 4{Cu(HL)(H 2O)(ClO 4)} 2] 2+ cations, non-coordinated perchlorate anions and crystal water molecules, held together by a network of hydrogen bonds. The central copper is in an elongated octahedral CuO 6 chromophore and the terminal copper atoms in distorted square-pyramidal CuNO 4 chromophores. Adjacent copper atoms are linked by carboxylate groups in a syn-anti conformation. From the magnetic susceptibility measurements, the complex is found to exhibit weak ferromagnetic interaction between nearest-neighbour copper(II) ions. The magnitude and nature of the exchange coupling are discussed on the basis of the structural data.