Bis- and mono-tridentate chelated iron complexes with a new facially capping unsymmetrical nitrogen ligand: X-ray structural and spectroscopic studies

Two new bis- and mono-tridentate chelated iron complexes, [FeII(LH)2](ClO4)2·C2H5OH (1) and [FeIII(LH)Cl3]·0.5CH2Cl2 (2), with facially capping N-tridentate ligand, 2-(5,7-dihydro-6H-dibenzo[c,e]azepin-6-yl)-N-(pyridin-2-ylmethyl)ethan-1-amine, incorporating biphenyl-append (LH), have been synthesized and characterized by X-ray crystal structure, spectroscopic (FTIR, UV–Vis and ESI-MS) and magnetic susceptibility measurements. Structure of 1 reveals pseudo-octahedral geometry around Fe(II) with two ligands (LH) arranged in trans-facial manner, in two crystallographic independent molecules, Mol. A and Mol. B, differing in biphenyl twist angles, ϕ = 43.7° and 45.1°. Complex 2 has similar geometry with Fe(III) having one facially capping ligand, LH and three chlorides (Cl−), also in two crystallographic independent molecules, Mol. A and Mol. B, differing by biphenyl twist angles, ϕ = 40.9° and −42.7°. The UV–Vis absorption spectrum of 2 in CH3CN suggests competitive coordination between the two weakly-coordinating tertiary amine nitrogen atoms having biphenyl-append, and the solvent, CH3CN. The qualitative magnetic susceptibility measurements for 1 and 2 at 296 K provide moments of 4.2 μB and 2.7 μB, respectively, suggesting nearly high-spin, Fe(II) (S = 2) and a rare intermediate-spin, Fe(III) (S = 3/2).