Cobalt(II) complexes of new biomimetic polydentate amide ligands. A spectroscopic,thermal and potentiometric study

Complexes of Co^II with N,N-bis-(3-carboxy-1-oxopropanyl)-1,2-ethylenediamine(L₁), N,N-bis-(3-carboxy-1-oxopropanyl)-1,2-phenylenediamine(L₂), N,N-bis-(2-carboxy-1-oxophenelenyl)-1,2-phenylenediamine(L₃) and N,N-bis-(3-carboxy-1-oxoprop-2-enyl)-1,2-phenylenediamine(L₄) have been prepared and characterized by elemental analysis, vibrational spectra, magnetic susceptibility measurements, electronic spectra and thermal studies. Stability constants of the complexes have been evaluated potentiometrically. Vibrational spectra indicate coordination of amide and carboxylate oxygens of the ligands along with two water molecules giving a MO₆ weak field octahedral chromophore. Electronic spectra support octahedral geometry around Co^II. The [Co(L₁)-(H₂O)₂] · 2H₂O complex has the maximum activation energy and [Co(L₃)(H₂O)₂] complex has the minimum activation energy. The order of stability constants of the Co^II complexes with various ligands is due to their -donor abilities.