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

Two dinuclear Cu(II) complexes of formula [Cu2(dpyam)2(μ-C2O4)(Cl)2] (1) and [Cu2(dpyam)2(μ-C2O4)(CF3SO3)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-C2O4)] units, while 2 contains chains of the dimeric [Cu2(dpyam)2(μ-C2O4)(CF3SO3)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 and2, respectively, in agreement with the coplanarity of the magnetic orbitals.