A novel trinuclear μ3-hydroxido-bridged Cu(II) compound; A molecular cluster, stabilized by hydrogen bonding, bridging pyrazolates, terminal pyrazoles, water and nitrate anions

Abstract

The synthesis, together with molecular structure and characterization of μ3-hydroxidobis(nitrato)tris(μ-pyrazolato)tetrakis(pyrazole) tricopper(II) monohydrate ([Cu3(OH)(pz)3(Hpz) 4(NO3)2](H2O)) is presented and discussed, also in comparison with some related pyrazole nitrate compounds. The peculiar intramolecular hydrogen-bond stabilization for the cluster with as many as 6 intramolecular hydrogen bonds is considered in detail. The non-bonding water solvate bridges between a coordinating nitrate and hydroxide, and intermolecularly with the pyrazole NH from a neighboring unit. Ligand-field, EPR and infrared spectra are discussed in the context of the trinuclear Cu unit. Low-temperature magnetic susceptibility shows a strong antiferromagnetic exchange, resulting in a spin of S = 1/2 at low T, similar to earlier reported related compounds. © 2014 Elsevier Ltd. All rights reserved.