Two new oxalato-bridged dinuclear copper(II) complexes with di-2-pyridylamine: crystal structures, spectroscopic and magnetic properties

Abstract

Two dinuclear Cu(II) complexes of formula [Cu 2(dpyam) 2(μ-C 2O 4)(Cl) 2] ( 1) and [Cu 2(dpyam) 2(μ-C 2O 4)(CF 3SO 3) 2] n ( 2) (dpyam = di-2-pyridylamine) have been synthesized and their spectroscopic and magnetic properties characterized. The structure of 1 is made up of the centrosymmetric dinuclear [{Cu(dpyam)(Cl)} 2(μ-C 2O 4)] units, while 2 contains chains of the dimeric [Cu 2(dpyam) 2(μ-C 2O 4)(CF 3SO 3) 2] units linked by the triflate anions. The two copper atoms in both compounds are linked through a bis-didentate oxalato group leading to a metal–metal separation of 5.526(1) and 5.228(3) Å. The stereochemistry of the Cu(II) chromophore in 1 is approximately square pyramidal, while compound 2 displays an elongated octahedral Cu(II) environment. The IR, ligand field and EPR measurements are in agreement with the structures found. The magnetic susceptibility measurements, measured from 5 to 350 K, revealed a very strong antiferromagnetic interaction between the Cu(II) atoms with a singlet–triplet energy gap ( J) of −274 and −342 cm −1, for compounds 1 and 2, respectively, in agreement with the coplanarity of the magnetic orbitals.