Copper(II) complexes of a series of alkoxy diazine ligands: mononuclear, dinuclear, and tetranuclear examples with structural, magnetic, and DFT studies.

Picolyl hydrazide ligands have two potentially bridging functional groups (μ-O, μ-N−N) and consequently can exist in different coordination conformers, both of which form spin-coupled polynuclear coordination complexes, with quite different magnetic properties. The complex [Cu2(POAP-H)Br3(H2O)] (1) involves a μ-N−N bridge (Cu−N−N−Cu 150.6°) and exhibits quite strong antiferromagnetic coupling (−2J = 246(1) cm-1). [Cu2(PZOAPZ-H)Br3(H2O)2] (2) has two Cu(II) centers bridged by an alkoxide group with a very large Cu−O−Cu angle of 141.7° but unexpectedly exhibits quite weak antiferromagnetic exchange (−2J = 91.5 cm-1). This is much weaker than anticipated, despite direct overlap of the copper magnetic orbitals. Density functional calculations have been carried out on compound 2, yielding a similar singlet−triplet splitting energy. Structural details are reported for [Cu2(POAP-H)Br3(H2O)] (1), [Cu2(PZOAPZ-H)Br3(H2O)2] (2), [Cu2(PAOPF-2H)Br2(DMSO)(H2O)]·H2O (3), [Cu4(POMP-H))4](NO3)4·2H2O (4), and PPOCCO (5) (a...