Abstract
The polydentate acyclic ligand 4-phenylpyrazole-5-carbaldehyde azine, H2L1, has been prepared and characterised. A second 4-phenylpyrazole-5-carbaldehyde derived ligand, H2L2, was prepared in situ by condensation with o-phenylendiamine. Two mononuclear iron(II) complexes, [Fe-II(HL2)(MeOH)(NCSe)]center dot H2O and [Fe II (H2L1)(2)](BF4)(2)center dot solvents, have been synthesised from 1 : 1 and 2 : 3 M: L reactions, respectively. No dinuclear, helical, species were obtained from 2 : 3 M: L reactions regardless of the solvent employed (MeOH, MeCN or NO2Me). An X-ray structure determination on the latter complex reveals that it is low spin at 90 K. Mossbauer spectra confirm this, and show that the former complex is, in contrast, high spin, even at 4.6 K.