A polymeric oxovanadium(IV) pyromellitate complex

The reaction of oxovanadium(IV) sulphate with 1,2,4,5-benzenetetracarboxylic acid (pyromellitic acid) in the presence of potassium carbonate yields a polymeric complex, K2[VO(pyr)]·6H2O (I) [pyr = pyromellitate(4-) ion]. The PM3(tm) calculations and IR spectroscopy suggest that the polymeric structure of I consists of -V-pyr-V-pyr- chains formed by the 1,4- or 1,5-bridging by the pyr ions. The chains are additionally cross-linked by the chelate function of one of the COO- groups of the pyr ion. Magnetic measurements do not reveal the presence of antiferromagnetic coupling between the V centers.