Behaviour of DFT-based approaches to the spin–orbit term of zero-field splitting tensors: a case study of metallocomplexes, MIII(acac)3 (M = V, Cr, Mn, Fe and Mo). Issue 44 (3rd November 2017)

• Record Type: Journal Article
• Authors: Sugisaki, Kenji; Toyota, Kazuo; Sato, Kazunobu; Shiomi, Daisuke; Takui, Takeji
• Is Part Of: Physical chemistry chemical physics. Volume 19:Issue 44(2017)
• Page Start: 30128
• Page End: 30138
• Publication Date: 2017-11-03
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp05533a
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : Zero-field splitting tensors of M III (acac)3 complexes are calculated using ab initio and DFT methods. Abstract : Spin–orbit contributions to the zero-field splitting (ZFS) tensor (D SO tensor) of M III (acac)3 complexes (M = V, Cr, Mn, Fe and Mo; acac = acetylacetonate anion) are evaluated by means of ab initio (a hybrid CASSCF/MRMP2) and DFT (Pederson–Khanna (PK) and natural orbital-based Pederson–Khanna (NOB-PK)) methods, focusing on the behaviour of DFT-based approaches to theD SO tensors against the valence d-electron configurations of the transition metal ions in octahedral coordination. Both the DFT-based approaches reproduce trends in theD tensors. Significantly, the differences between the theoretical and experimental D ( D = D ZZ − ( D XX + D YY )/2) values are smaller in NOB-PK than in PK, emphasising the usefulness of the natural orbital-based approach to theD tensor calculations of transition metal ion complexes. In the case of d 2 and d 4 electronic configurations, the D SO (NOB-PK) values are considerably underestimated in the absolute magnitude, compared with the experimental ones. TheD SO tensor analysis based on the orbital region partitioning technique (ORPT) revealed that theD SO contributions attributed to excitations from the singly occupied region (SOR) to the unoccupied region (UOR) are significantly underestimated in the DFT-based approaches to all the complexes under study. In the case of d 3 and d 5 configurations, the (SOR → UOR) excitations contribute in a nearly isotropic manner, which causes fortuitous error cancellations in the DFT-based D SO values. These results indicate that more efforts to develop DFT frameworks should be directed towards the reproduction of quantitativeD SO tensors of transition metal complexes with various electronic configurations and local symmetries around metal ions.