Investigations on the Spin States of Two Mononuclear Iron(II) Complexes Based on N-Donor Tridentate Schiff Base Ligands Derived from Pyridine-2,6-Dicarboxaldehyde
Abstract
Iron(II)-Schiff base complexes are a well-studied class of spin-crossover (SCO) active species due to their ability to interconvert between a paramagnetic high spin-state [HS, S = 2, (5)T(2)] and a diamagnetic low spin-state [LS, S = 0, (1)A(1)] by external stimuli under an appropriate ligand field. We have synthesized two mononuclear Fe(II) complexes, viz., [Fe(L1)(2)](ClO4)(2).CH3OH {1} and [Fe(L2)(2)](ClO4)(2).2CH(3)CN {2}, from two N(6)-coordinating tridentate Schiff bases derived from 2,6-bis[(benzylimino)methyl]pyridine.
The complexes have been characterized by elemental analysis, electrospray ionization-mass spectrometry (ESI-MS), Fourier-transform infrared spectroscopy (FTIR), solution state nuclear magnetic resonance spectroscopy, (1)H and (13)C NMR (both theoretically and experimentally), single-crystal diffraction and magnetic susceptibility studies. The structural, spectroscopic and magnetic investigations revealed that 1 and 2 are with Fe-N(6) distorted octahedral coordination geometry and remain locked in LS state throughout the measured temperature range from 5-350 K.