Synthesis, hydrogen-bonded 1D structure, and abrupt spin transition between high-spin (HS) and an ordered [HS–HS–HS–LS] of a mononuclear iron(III) complex [FeIII(Him)2(4-MeOhapen)]CF3SO3 (Him = imidazole, 4-MeOhapen = N,N′-bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine)

Abstract A SCO iron(III) complex [Fe III (Him) 2 (4MeOhapen)]CF 3 SO 3 was synthesized, where Him = imidazole and 4-MeOhapen =  N , N ′-bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine. Fe III ion has an octahedral coordination geometry with N 2 O 2 donor atoms of the equatorial tetradentate ligand (4-MeOhapen) and two nitrogen atoms of two imidazoles (Him) at the axial positions. The adjacent cations are bridged by CF 3 SO 3 − ion through NH⋯O hydrogen bonds between Him and CF 3 SO 3 − to give a one-dimensional chain structure {[Fe III (Him) 2 (4MeO-hapen)]CF 3 SO 3 } 1∞ . The magnetic susceptibility measurements showed that complex exhibits an abrupt spin transition between a single HS phase and a symmetry-breaking [HS–HS–HS–LS] phase and another transition around 80 K. The single-crystal X-ray analyses at 296 and 150 K revealed the structures at a single HS and [HS–HS–HS–LS] states.