Low-spin iron(III) complexes of a tetradentate bis-amide ligand and X-ray crystal structure of trans-[Fe(bpc)(1-MeIm)2]ClO4 (H2bpc=4, 5-dichloro-1, 2-bis(2-pyridinecarboxamido)benzene; 1-MeIm=1-methylimidazole)