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Comparison of density functionals for the study of the high spin low spin gap in Fe(III) spin crossover complexes
Author(s) -
Sirirak Jitnapa,
Sertphon Darunee,
Phonsri Wasinee,
Harding Phimphaka,
Harding David J.
Publication year - 2017
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.25362
Subject(s) - chemistry , basis set , spin crossover , enthalpy , density functional theory , spin states , crystallography , standard enthalpy of formation , spin (aerodynamics) , computational chemistry , inorganic chemistry , thermodynamics , physics
A detailed investigation of the accuracy of different quantum mechanical methods for the study of iron(III) spin crossover complexes is presented. The energy spin state gap between the high and low spin states; Δ E (HS‐LS) of nine iron(III) quinolylsalicylaldiminate complexes were calculated with nine different DFT functionals, then compared. DFT functionals: B3LYP, B3LYP‐D3, B3LYP*, BH&HLYP, BP86, OLYP, OPBE, M06L, and TPSSh were tested with six basis sets: 3‐21G*, dgdzvp, 6‐31G**, cc‐pVDZ, Def2TZVP, and cc‐pVTZ. The cations from the X‐ray crystal structures of [Fe(qsal‐OMe) 2 ]Cl·MeCN·H 2 O, [Fe(qsal‐OMe) 2 ]Cl·2MeOH·0.5H 2 O, [Fe(qsal‐OMe) 2 ]BF 4 ·MeOH, [Fe(qsal‐OMe) 2 ]NCS·CH 2 Cl 2 , [Fe(qsal‐F) 2 ]NCS, [Fe(qsal‐Cl) 2 ]NCS·MeOH, [Fe(qsal‐Br) 2 ]NCS·MeOH, [Fe(qsal‐I) 2 ]OTf·MeOH, and [Fe(qsal) 2 ]NCS⋅CH 2 Cl 2 were used as starting structures. The results show that B3LYP, B3LYP‐D3, OLYP, and OPBE with a 6‐31G**, Def2TZVP, and cc‐pVTZ basis set give reasonable results of Δ E (HS‐LS) compared with the experimental data. The enthalpy of [Fe(qsal‐I) 2 ] + calculated with an OLYP functional and cc‐pVTZ basis set (1.48 kcal/mol) most closely matches the experimental data (1.34 kcal/mol). B3LYP* yields an enthalpy of 5.92 kcal/mol suggesting it may be unsuitable for these Fe(III) complexes, mirroring recent results by Kepp ( Inorg . Chem ., 2016, 55 , 2717–2727).