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 [Fe III (Him) 2 (4-MeOhapen)]CF 3 SO 3 (Him=imidazole, 4-MeOhapen= N , N ′-bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine)

A SCO iron(III) complex [FeIII(Him)2(4MeOhapen)]CF3SO3 was synthesized, where Him=imidazole and 4-MeOhapen=N,N′-bis(2-oxy-4-methoxyacetophenylidene)ethylenediamine. Adjacent cations are bridged by a CF3SO3− ion through NH⋯O hydrogen-bond between Him and CF3SO3− to give a one-dimensional chain structure {[FeIII(Him)2(4MeO-hapen)]CF3SO3}1∞. The magnetic susceptibility measurements and the single-crystal X-ray analyses revealed a symmetry-breaking spin transition between HS and an ordered [HS–HS–HS–LS] phases.