Synthesis, characterization and crystal structure of a new tripodal ligand containing imidazole and phenolate moieties and its iron(III) complexes

Abstract

The new tripodal ligand N-(2′-hydroxybenzyl)- N, N-bis(2-benzimidazolylmethyl)amine (LH) and its iron(III) complexes Fe(L) (N 3) · Py (1), Fe(L) (Mim) 2(ClO 4) 2 ( 2) (where Min = N-methylimidazole) and Fe(L) (Cl) 2·H 2O ( 3) have been prepared and characterized by analytical, spectroscopic and electrochemical methods. The structure of 1·C 6H 14 has been determined by X-ray crystallography. Complex 1·C 6H 14 crystallizes in the monoclinic space group P2/n with a = 13.821 (3), b = 13.675 (3), c = 16.424 (5) A ̊ β = 96.08(3)°, Z = 4 and R = 0.083 for 1476 reflections with I > 3 σ( I). The UV-Vis spectroscopic and electrochemical results show that the energy of the ligand-to-iron(III) charge transfer ( LMCT) bands and Fe(III)/Fe(II) redox potentials are sensitive to the field strength of the other ligands coordinated to the ferric center. As the other ligand field strength increases, the LMCT bands are blue-shifted and the Fe(III)/Fe(II) redox potentials become more negative. The Mössbauer spectrum of 1 shows that the isomer shift ( σ = 0.31 mm s −1) and quadrupole splitting ( ΔE Q = 0.64 mm s −1) are similar to those found in Fe 2Tf and Fe 2Lf proteins.