Spin Crossover of a Langmuir−Blodgett Film Based on an Amphiphilic Iron(II) Complex

An amphiphilic iron(II) complex [Fe II L 2 (NCS) 2, where L is a substituted bipyridine] exhibiting a thermal spin-crossover phenomenon around room temperature is chemically unstable at the gas−water interface. However, it forms a perfectly stable Langmuir film when formamide−water mixtures are used as a subphase. After transfer onto a solid substrate, a well-defined Langmuir−Blodgett (LB) film was then obtained. Infrared spectroscopy at variable temperature showed that the spin conversion still occurs in this lamellar material. The specific organization imposed by the LB technique leads to a surroundings effect demonstrated, in particular, by thermal cycles. The understanding of this effect is crucial to control any thermal or light-induced spin conversion within an LB film.