Synthesis of polynuclear copper(II) complexes by controlling the conformation ( cis or trans) of N, N′-bis(3-aminopropyl) oxamidate and the coordination mode of 2,2′-bipyrimidine

Abstract

The synthesis, molecular structure and magnetic properties of three new polynuclear copper(II) complexes, [Cu( cis-oxpn)Cu(bpm)]- (ClO 4) 2·CH 3OH ( 1), [Cu 2( trans-oxpn) (bpm) 2](ClO 4) 2·2H 2O ( 2) and [Cu 2( trans-oxpn)( μ-bpm)](ClO 4) 2·2.5H 2O ( 3) are reported. The compounds were prepared by controlling the conformation ( cis or trans) of oxpn ( N, N′-bis(3-aminopropyl)oxamidate and the coordination mode (bi- or bisbidentate) of bpm (2,2′-bipyrimidine). Complex 1 is a dinuclear complex in which the copper(II) ions are bridged by a cis-oxamidate group and where bpm acts as a bidentate terminal ligand. 2 is a trans-oxamidate-bridged dinuclear copper(II) complex with two bidentate terminal bpm molecules. In 3, a bisbidentate bpm molecule connects the dinuclear Cu 2( trans-oxpn) units to generate an alternating oxamidate-bpm polynuclear copper(II) chain complex. Magnetic susceptibility measurements reveal the occurrence of strong antiferromagnetic exchange couplings for the three compouns with J values of −386.0 and −328.9 cm −1 for 1 and 2, respectively, and J = −340.0 cm −1, with an alternation parameter α = 0.24, for 3. Magnetic parameters are discussed on the basis of the structural results and compared with those of related complexes.