Auxiliary alkyl chain modulated spin crossover behaviour of [Fe(H2Bpz2)2(Cn-bipy)] complexes. Issue 37 (26th July 2021)

• Record Type: Journal Article
• Authors: Guo, Yunnan; Rotaru, Aurelian; Müller-Bunz, Helge; Morgan, Grace G.; Zhang, Shishen; Xue, Shufang; Garcia, Yann
• Is Part Of: Dalton transactions. Volume 50:Issue 37(2021)
• Page Start: 12835
• Page End: 12842
• Publication Date: 2021-07-26
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/d1dt01787j
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : The length of the alkyl chain substituents employed in complexes [Fe(H2 Bpz2 )2 (C n -bipy)] can have a large impact on the transition temperature and solid state spin crossover profile. Abstract : Three new alkyl chain substituted complexes [Fe(H2 Bpz2 )2 (C n -bipy)] (pz = pyrazolyl, C n -bipy = bipyridine alkyl chain diester, n = 3 (3 ), 4 (4 ) and 5 (5 )) show versatile spin state switching behaviour with different "tail" lengths as revealed by structural and magnetic analyses. The most striking phenomenon is observed for 5 which undergoes an abrupt spin transition accompanied by thermal hysteresis of ca. 10 K, which is attributed to crystal packing effects derived from the competition between π⋯π and C–H⋯O interactions. Interestingly, each of the complexes exhibits similar gradual and complete spin crossover in methanol solution with a transition temperature around 249 K, as deduced from temperature-dependent UV-vis spectroscopy. This highlights the differences between the solid state (ligand field; crystal packing) and solution (ligand field; solvation) effects on spin crossover. This work demonstrates that the length of the complex's alkyl chain substituents on the complex can have a large impact on the transition temperature and profile of solid state spin crossover, offering a potential path to the fabrication of soft matter spin crossover materials.