Syntheses, hydrogen-bonded assembly structures, and spin crossover properties of [FeIII(Him)2(n-MeOhapen)]PF6 (Him = imidazole and n-MeOhapen = N,N′-bis(n-methoxy-2-oxyacetophenylidene)ethylenediamine); n = 4, 5, 6)

Abstract

Three iron(III) complexes, [FeIII(Him)2(n-MeOhapen)]PF6 (1: n=4, 2: n=5, 3: n=6), where Him=imidazole and n-MeOhapen=N,N′-bis(n-methoxy-2-oxyacetophenylidene)ethylenediamine, were synthesized. Each FeIII ion was coordinated by N4O2 donor atoms of equatorial n-MeOhapen and two axial Him. The saturated FeC2N2 chelate ring involving the ethylenediamine moiety adopted a gauche conformation and the two phenylidene planes of [FeIII(Him)2(n-MeOhapen)]+ were oriented opposite to the FeO2N2 coordination plane. Two adjacent [FeIII(Him)2(4-MeOhapen)]+ cations in 1 were connected via PF6− ions by hydrogen bonds between the imidazole group and PF6− to give a one-dimensional chain. Two adjacent cations in 2 were connected via hydrogen bonds between the phenylidene oxygen and imidazole atoms to form a cyclic dimer structure. Two EtOH molecules were involved in a hydrogen-bonded cyclic dimer structure in 3. Compounds 1 and 2 showed spin crossover behavior, but 3 showed incomplete spin crossover.