Aryl-Substituent Effects on Spin Crossover in [Fe(H2Bpz2)2(bipy-R)] Complexes: Structure -Magnetism Correlations

Spin crossover (SCO) materials reversibly switch between high-spin and low-spin states in response to external stimuli, accompanied by pronounced changes in electronic, magnetic, and optical properties, underpinning their potential in data storage, sensing, and molecular electronics.1-3 Spin transition behavior is influenced by ligand field and cooperative interactions, necessitating systematic studies to understand the structure-SCO property relationship.4 Aryl groups, characterized by their unique π-conjugation, steric effects, and fluorescence properties, play a crucial role in modulating the structure, electronic behavior and photophysical properties of complexes. In this work, we introduce phenyl (phen), 1-naphthyl (1-nap), 2-naphthyl (2-nap), and anthryl (an) groups into the SCO complex [Fe(H2Bpz2)2(bipy)],5 to afford four Fe(II) complexes [Fe(H2Bpz2)2(bipy-R)] (R = phen, 1; R = 1-nap, 2; R = 2-nap, 3; R = an, 4) and investigated their SCO properties (Scheme 1). Complexes 1 and 3 undergo one-step SCO with ~57%/50% completeness and T1/2 = 139 K/152 K. Complexes 2 and 4 exhibit two-steps gradual SCO with ~45%/30% completeness (T1/2 = 242 K/289 K) for the first step and ~29%/50% completeness (T1/2 = 137 K/176 K) for the second step revealed by magnetic measurements. The different SCO behaviors are attributed to the electronic effects of substituents and the unique crystal stacking patterns, involving π··· π interactions.

Affiliations

UCLouvainSST/IMCN/MOST - Molecular Chemistry, Materials and Catalysis

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Wang, M., Robeyns, K., Garcia, Y., & et al. (2026, June 11). Aryl-Substituent Effects on Spin Crossover in [Fe(H2Bpz2)2(bipy-R)] Complexes: Structure -Magnetism Correlations. ICMES 2026, Saïdia. https://hdl.handle.net/2078.5/277422