A Hydrogen Bond Motif Giving a Variety of Supramolecular Assembly Structures and Spin-Crossover Behaviors

A series of spin-crossover (SCO) iron­(II) compounds, fac-[FeII(HLR)3]­Cl·PF6 [R = methyl (Me, 1), ethyl (Et, 2), n-propyl (n-Pr, 3), n-butyl (n-Bu, 4), and n-pentyl (n-Pen, 5)], were synthesized, where HLR denotes a series of [(2-methylimidazol-4-yl)­methylidene]­monoalkylamines. The cations fac-[FeII(HLR)3]2+ and chloride anions associate through 3:3 imidazole···chloride hydrogen bonding. This hydrogen-bonding motif gives rise to a variety of assembly structures consisting of a one-dimensional ladder for 3 and 4, two kinds of two-dimensional networks for 1 and 2, and a cubane-like structure for 5. The compounds exhibit various types of SCO transitions between high-spin (S = 2) and low-spin (S = 0) states as a result of their intermolecular interactions.