Abstract

A series of Fe(II) complexes, fac-[Fe(4-ima-Bp) <inf>3</inf> ](Y) <inf>2</inf> ·sol (Y = ClO <inf>4</inf> ; sol = 3EtOH 1, 3MeOH 2; Y= BF <inf>4</inf> ; sol = EtOH·4H <inf>2</inf> O 3, 4H <inf>2</inf> O 4 and 3.5MeCN 5) have been prepared and structurally and magnetically characterized. The low temperature structures of 1, 2 and 5 have been determined by X-ray crystallography with LS Fe(II) centres found in all cases. Extensive C–H···π interactions between the cations form 2D layers, which are linked to one another through N-H···O and O-H···O hydrogen bonds, resulting in high cooperativity. Despite 5 containing MeCN, N-H···O/F hydrogen bonds, and C–H···π and π-π interactions combine to give similar 2D layers. Magnetic measurements reveal moderately abrupt spin crossover for 1-4; becoming more gradual and only 50% complete in 1 due to solvent loss. The MeCN solvate shows more gradual SCO and reinforces how subtle changes in packing can significantly influence SCO behaviour.