Validating and analyzing EPR hyperfine coupling constants with density functional theory

TY - JOUR

T1 - Validating and analyzing EPR hyperfine coupling constants with density functional theory

AU - Hedegård, Erik D.

AU - Kongsted, Jacob

AU - Sauer, Stephan P. A.

PY - 2013/5/14

Y1 - 2013/5/14

N2 - This paper focuses on the calculation of the (isotropic) hyperfine coupling tensor, AisoK, which consists of the Fermi contact term (AFC K) and a spin orbit correction, the pseudocontact term (APC K). Using the aug-cc-pVTZ-J basis set, we test a range of correlation exchange functionals against experimental values for a series of first row transition metal complexes. This has been done both with (AisoK = AFCK + APCK) and without (AisoK = AFC K) spin orbit coupling included. Overall, hybrid functionals perform best, although some exceptions are found. Furthermore, we analyze molecular orbital contributions to the Fermi contact term. We find a great difference in the relative magnitude of contributions from frontier orbitals and inner or outer-core orbitals. Complexes, where the frontier orbital contribution exceeds the core-orbital contributions, are always small, ionic complexes ("class 1"). For these complexes, the computational requirements with respect to the one-electron basis set are not severe, and regular basis sets such as aug-cc-pVTZ provide reasonable results. Unfortunately, the core contributions to AFCK are either comparable ("class 2") or far exceed ("class 3") the contributions from the frontier orbitals in both organometallic and traditional coordination complexes. Agreement with experimental results can for these complexes only be obtained by use of specialized core-property basis sets such as the aug-cc-pVTZ-J basis set.

AB - This paper focuses on the calculation of the (isotropic) hyperfine coupling tensor, AisoK, which consists of the Fermi contact term (AFC K) and a spin orbit correction, the pseudocontact term (APC K). Using the aug-cc-pVTZ-J basis set, we test a range of correlation exchange functionals against experimental values for a series of first row transition metal complexes. This has been done both with (AisoK = AFCK + APCK) and without (AisoK = AFC K) spin orbit coupling included. Overall, hybrid functionals perform best, although some exceptions are found. Furthermore, we analyze molecular orbital contributions to the Fermi contact term. We find a great difference in the relative magnitude of contributions from frontier orbitals and inner or outer-core orbitals. Complexes, where the frontier orbital contribution exceeds the core-orbital contributions, are always small, ionic complexes ("class 1"). For these complexes, the computational requirements with respect to the one-electron basis set are not severe, and regular basis sets such as aug-cc-pVTZ provide reasonable results. Unfortunately, the core contributions to AFCK are either comparable ("class 2") or far exceed ("class 3") the contributions from the frontier orbitals in both organometallic and traditional coordination complexes. Agreement with experimental results can for these complexes only be obtained by use of specialized core-property basis sets such as the aug-cc-pVTZ-J basis set.

KW - Faculty of Science

KW - EPR spectroscopy

KW - Computational Chemistry

KW - Quantum Chemistry

KW - Transition metal complex

KW - density functional theory

U2 - 10.1021/ct400171c

DO - 10.1021/ct400171c

M3 - Journal article

C2 - 26583728

SN - 1549-9618

VL - 9

SP - 2380

EP - 2388

JO - Journal of Chemical Theory and Computation

JF - Journal of Chemical Theory and Computation

IS - 5

ER -