Coordination properties between two new tailed porphyrin iron (III) complexes, 5[o-(4-(1-imidazolyl)butoxy)phenyl]-10,15,20-triphenylporphyrinatoiron (III) chloride {[Fe^I^I^I(ImTPP)]Cl} and 5-[p-(4-(3-pyridyloxyl)butoxyl]phenyl-10,15,20-triphenylporphyrinatoiron (III) chloride {[Fe^I^I^I(PyTPP)]Cl}, with nitrogenous ligands and the equilibrium constants for the addition of these ligands to [Fe^I^I^IP]Cl in chloroform were studied by spectral technique. Experimental results demonstrated that [Fe^I^I^I(PyTPP)]Cl, just similar to [Fe^I^I^I(TPP)]Cl, form 1:2 adducts with imidazole or pyridines, respectively, but (Fe^I^I^I(ImTPP)]Cl forms only 1:1 adducts with pyridines and form 1:2 adduct with imidazole. The equilibrium constants for the addition of nitrogenous ligands to [Fe^I^I^I(ImTPP)]Cl are 10-10^3 times as big as those for [Fe^I^I^I(TPP)]Cl system. We believe that this result is from the fact that the axial coordination of these ligands to [Fe^I^I^I(ImTpp)]Cl induces the coordination of terminal imidazole group with ferric iron in [Fe^I^I^I(ImTpp)]Cl and this kind of coordination mode strengthens the bonding between ferric ion in [Fe^I^I^I(ImTpp)]Cl and nitrogen atom in ligand. The novel coordination mode and its structure were identified by the experimental data from UV-vis, ^1H NMR and low-temperature EPR.

Key words: ULTRAVIOLET SPECTROPHOTOMETRY, SPECTROPHOTOMETRY, IRON COMPLEX, PYRIDINE, IMIDAZOLE, PROTON MAGNETIC RESONANCE SPECTROMETRY, PORPHYRIN