Theoretical calculation and prediction for experimental design to obtain spin crossover complexes

Abstract

DFT methods were utilized to study SCO complexes. [Fe(2btz)2(NCX)2] (2btz = 2,2′‐bithiazoline, X = S (1) and Se (2)), [Fe(phen)2(NCX)2] (phen = 1,10‐phenantroline, X = S (3) and Se (4)), and [Fe(bpy)2(NCS)2] (5) (bpy = 2,2′‐bipyridine) compounds, which have experimentally shown SCO behavior, were calculated. B3LYP, B3LYP*, OPBE, and OLYP with 6‐31G* and 6‐311 + G** basis sets were employed to calculate the ΔEHS/LS energy gap as a clue to find complexes with SCO behavior. It is found that calculated result by B3LYP* with c3 = 0.14 and OPBE methods and 6‐31G* basis set are in agreement with experimentally observed SCO complexes. Then, newly designed Fe(N‐N)2(X)2 complexes, where N‐N are bidentate nitrogen donor chelating ligands and X= SCN‐, SeCN‐, Cl‐, Br‐, I‐, were chosen to see their potential to be SCO compounds. ΔEHS/LS for potential SCO complexes are estimated from 0.8 to 6.5 kcal/mol in B3LYP* and 0.6–5.7 kcal/mol in OPBE. These calculations suggest [Fe(bpy)2(NCSe)2], [Fe(5dmbpy)2(NCS)2], and [Fe(3‐BrPhen)2(NCSe)2] compounds have the ability to show SCO behavior. © 2016 Wiley Periodicals, Inc.