Biomimetic polyimidazole complexes: A thermoanalytical study of Co(II)-, Ni(II)- and Cu(II)-bis(imidazol-2-yl)methane complexes

Imidazole rings of histidine residues often form part of the metal-binding site in metalloproteins, so ligands with the 2-imidazolyl units are good models for mimicking biological metal-binding sites because the histidine imidazole ring is often attached via the 2-position to the side chain when the imidazole is coordinated to a metal. Thermoanalytical studies on biomimetic molecules are useful to complete the informations on the mechanism of action of the metal-binding sites of metalloproteins and to relate their chemico-physical properties. The synthesis, the spectroscopic characterization and the thermoanalytical study of bis(imidazol-2-yl)methane (BIM) complexes with divalent cobalt, nickel and copper, with a general formula M(BIM)2Cl2, are reported: the thermal stability and the decomposition steps were determined by thermogravimetry (TG), derivative thermogravimetry (DTG) and differential scanning calorimetry (DSC). The released products, due to the thermal decomposition, were analysed by on-line coupling a FTIR spectrometer to the thermobalance; the so obtained evolved gas analysis (EGA) allowed to prove the proposed decomposition steps.