An unusual half-open cubane-like tetranuclear copper(II) complex supported by both μ-alkoxo and μ3-hydroxo bridges: Structure, magnetic properties, EPR and DFT studies

The compound 4-methyl-2,6-bis[(2-(pyridin-2-yl)hydrazinylidene)methyl]phenol (H-PHMP) was prepared by the direct condensation of 2,6-diformyl-4-methylphenol (PCDA) and 2-hydrazinopyridine. It reacts with copper(II) nitrate to yield a self-assembled, both alkoxo- and hydroxo-bridged, tetranuclear homoleptic copper(II) complex, [Cu-4(PHMP)(2)(mu(3)-OH)(2)(NO3)(2)](NO3)(2)center dot 9H(2)O (1), with a [Cu-4(mu-O)(2)(mu(3)-OH)(2)](4+) half-open cubane core. Compound 1 is composed of two dinuclear [Cu-2(PHMP)] units linked by the two p.-bridging alkoxide oxygen atoms of the PCDA backbone. Variable temperature magnetic susceptibility measurements indicate the existence of antiferromagnetic exchange interactions (J(1) = -304.0 cm(-1), J(2) = 127.3 cm(-1) and g = 2.05) in complex 1. The exchange pathway parameters were also evaluated from density functional theoretical calculations and fully agree with the experimental findings. (C) 2013 Elsevier Ltd. All rights reserved.