Crystal Structures and Spin-Crossover Behavior of Iron(II) Complexes with Chiral and Racemic Ligands

Abstract

Chiral iron(II) complexes, [Fe{(R)-L}2(NCS)2] (1) and [Fe{(S)-L}2(NCS)2] (2), and racemic complex [Fe(rac)-L)2(NCS)2] (3) {L = α-methyl-N-(2-pyridinylmethylene)cyclohexanemethanamine} were synthesized. Their structures and magnetic properties were investigated by X-ray crystallography, magnetic susceptibility measurements, and Mössbauer spectroscopy. Complexes 1 and 2 crystallize in the trigonal system with space group P3121 and P3221, respectively. All complexes exhibit spin-crossover (SCO) behavior and light induced excited spin state trapping (LIESST) effects at 532 nm. Complexes 1 and 2 show similar gradual SCO behavior, and complex 3 shows more gradual SCO, which seems to be a result of the different crystal packing, as complex 3 is the symmetric isomer but 1 and 2 are asymmetric.