A DFT and Mössbauer spectroscopy investigation of spin‐crossover iron(II) complexes with 2,6‐bis(1H‐imidazol‐2‐yl)pyridines

Abstract

AbstractA quantum chemical study was carried out for a number of iron(II) complexes [FeL2]Ai·nH2O (L = 2,6‐bis(1H‐imidazole‐2‐yl)pyridine (L1); 2,6‐(4,5‐dimethyl‐1H‐imidazole‐2‐yl)pyridine (L2); 2,6‐bis(1H‐benzimidazole‐2‐yl)pyridine (L3); A = ReO4−, B10H102−, B12H122−; n = 0–2). These complexes exist in the low spin (LS) form 1A1 (total electron spin S = 0) at room temperature and switch to the high spin (HS) form 5T2 (S = 2) upon heating. The experimental isomeric shift and quadrupole splitting values for compounds with L2 exceed those for compounds with L1 and L3 by <0.02> mm/s and <0.1> mm/s, respectively (for LS forms). Such a discrepancy between MS parameters can be explained by the assumption that chemical bonding between the iron ion and the surrounding nitrogen atoms in the compounds with L2 may be more ionic in character than that in the compounds with L1 and L3. At the same time, the results obtained with the TPSSh hybrid meta‐GGA functional gave a better agreement with the experimental data than those obtained with the B3LYP exchange‐correlation functional.