Synthesis, mixed-spin-state structure and Langmuir–Blodgett deposition of amphiphilic Fe(iii) quinolylsalicylaldiminate complexes

Abstract

Designing and integrating Fe(III)-based spin crossover (SCO) complexes onto substrates remains a challenging goal with only a handful of examples reported. In this work, we successfully synthesized and characterized three [Fe(qsal-OR)₂]NO₃ (qsal-OR = 5-alkoxy-2-[(8-quinolylimino)methyl]phenolate) complexes, in which R = C₁₂H₂₅ 1, C₁₆H₃₃ 2, and C₂₂H₄₅ 3 to explore the impact of alkyl chain on the modulation of SCO activity and potential for self-assembly on a glass surface. The SCO is found to be gradual and incomplete in all cases, with the LS state more stabilised as the alkyl group shortens. We also demonstrate that all complexes form stable Langmuir films and achieve good transfer ratios to the glass surface, with 2 being the best in terms of stability. This paves the way for the SCO modulation of complexes in this class and the development of SCO devices.