Syntheses, structures, and magnetic properties of copper(II) complexes with 1,3-[bis(2-pyridylmethyl)amino]benzene (1,3-tpbd) as ligand.

The dinuclear copper(II) complexes {[Cu2(1,3-tpbd)- (H2O)(OAc)2](ClO4)2}0.23{[Cu2(1,3-tpbd)(H2O)2(OAc)]- (ClO4)3}0.77·0.77H2O (1), [Cu2(1,3-tpbd)(H2O)2(OAc)2]- (ClO4)2·2H2O (2), and the tetranuclear copper(II) complex [Cu4(1,3-tpbd)2(H2O)2(SO4)4]·8H2O (3) {1,3-tpbd = 1,3- bis[bis(2-pyridylmethyl)amino]benzene} were synthesised and structurally characterised by X-ray diffraction. Variable temperature (2.0-290 K) magnetic susceptibility measurements on these complexes as well as on the dinuclear copper(II) complex [Cu2(1,3-tpbd)(H2O)2(ClO4)3]ClO4 (4) (whose structure was published earlier) were performed. In contrast to 2 and 3, significant ferromagnetic coupling with J = +9.3 cm-1 was observed for 4 (the Hamiltonian being defined as Hˆ = -J Sˆ 1·Sˆ 2). Density functional theory (DFT) calculations were used successfully for the interpretation of the ferromagnetic coupling observed in 4