Impact of the Schiff Base Ligand Substituents on the Solid State and Solution Properties in Eleven Iron(III) Complexes
Investigations on a series of mononuclear iron(III) Schiff base complexes of general formula [Fe(L)Cl]·S (where L2- is Schiff base ligand anion, S is a solvent molecule) are reported. Derivatives of salicylaldehyde or 2-hydroxy-1-naphtaldehyde were used in combination with a linear either symmetrical or non-symmetrical aliphatic triamines to synthesize the Schiff base ligands and the consecutive reactions with iron(III) chloride afforded various [Fe(L)Cl] complexes. Compounds were characterized by conventional techniques and the crystal structures of all complexes have been determined as well. Structural study has revealed relationship between the spatial arrangement of N3O2-donor atom set and length of the aliphatic part of Schiff base ligand. Magnetic and EPR investigation confirmed the high spin state behaviour in all reported compounds and their analysis allowed to quantify the parameters of spin Hamiltonian. Formation of hydrogen-bonded pseudodimers with antiferromagnetic exchange coupling was found in the complexes with the shortest aliphatic part of Schiff base ligands. Experimental exchange coupling constants are in good agreement with those obtained from DFT calculation and correlate with the strength of the hydrogen bonds. Cyclic and square wave voltammetry were employed to investigate the redox properties of reported compounds and the experimental redox potentials were compared with those obtained from the DFT calculations.