Synthesis, characterisation and magnetic properties of copper(II) complexes with 3-hydroxypicolinic acid (HpicOH): the crystal structure of [Cu(picOH)2(BPE)]2·[Cu(picOH)2(BPE)2]·8H2O

A novel 1D coordination polymer, [Cu(picOH)2(BPE)] (IIa), and neutral [Cu(picOH)2(BPE)2] (IIb) complexes, can be simultaneously isolated (structure II) when neutral [Cu(picOH)2] (I) species are axially bridged by 1,2-bis(4-pyridyl)ethane (BPE) molecules. The compound has been characterised structurally using single-crystal X-ray diffraction, elemental analysis, infrared and Raman spectroscopies and thermoanalytical measurements. In both structures the 3-hydroxypicolinate ligands are coordinated to the Cu2+ centres through their typical N,O-chelating coordination, with the increase of coordination number in II leading to a typical Jahn-Teller distorted octahedral coordination geometry. Although the structure of I has already been reported, we have re-determined its single-crystal structure at the low temperature of 180(2) K for comparative purposes. The magnetic properties of both compounds have also been investigated.