Spectral properties of some metal complexes derived from uracil–thiouracil and citrazinic acid compounds

The reaction of FeCl3 with uracil (H2L1), citrazinic acid (H2L6), 5-(phenylazo)citrazinic acid (H2L7), 5-(m-hydroxyphenylazo)citrazinic acid (H2L8) and 5-(m-nitrophenylazo)citrazinic acid (H2L9) leads to the formation of complexes with the empirical formula Fe(HL)3·nH2O (n = 1–3). All of the prepared complexes have octahedral complexation geometry where the azo group is not the reactive site for complexation. Thiouracil (H2L2) and the 5-(substituted phenylazo)thiouracil (H2L3–H2L5) ligands are bidentates on complexation with Co(II), Ni(II) and Cu(II). The complexes have been characterized by elemental analyses, IR, electronic spectra, magnetic susceptibility, DTA, electron spin resonance (copper complexes) and Mössbauer spectra (iron complexes). The coordination bond lengths between the metal ion and the active centers for complexation were calculated.