Ab Initio Analysis of Metal–Ligand Bonding in An(COT)2 with An=Th, U in Their Ground‐ and Core‐Excited States. Issue 8 (13th January 2020)

• Record Type: Journal Article
• Authors: Ganguly, Gaurab; Sergentu, Dumitru‐Claudiu; Autschbach, Jochen
• Is Part Of: Chemistry. Volume 26:Issue 8(2020)
• Page Start: 1776
• Page End: 1788
• Publication Date: 2020-01-13
• Subjects: actinocenes -- core-excited states -- metal–ligand bonding -- multi-reference approaches -- XANES; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201904166
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Relativistic multireference ab initio wave function calculations with the restricted active space second‐order perturbation theory (RASPT2) were performed on thorocene and uranocene to determine the actinide N4, 5 ‐edge and carbon K‐edge X‐ray absorption near‐edge structure (XANES) intensities and the metal–ligand orbital mixing in the ground state and core‐excited states. Calculated spectral intensities show very good agreement with the experiments and therefore allow detailed and unambiguous assignment of the observed spectral features. φ ‐type covalent bonding or antibonding interactions are observed for thorocene in the core‐excited states, though not in the ground state. This is because the molecular orbital of φ symmetry, which is the in‐phase combination of the ligand L φ and the Th 5f φ orbitals, can be populated with electrons in core‐excited states, whereas it is essentially unoccupied in the ground state. For uranocene, the XANES spectra do not reveal much information beyond multiplet broadening, despite the presence of distinct peaks in the spectra. Every core‐excited peak is best characterized by its own set of bond orbitals, as the excited state covalency is clearly different from the ground state covalency. Abstract : φ ‐bonding in Actinocenes from Ab‐Initio XANES : X‐ray absorption near‐edge structure (XANES) intensities in An(COT)2 (An=Th, U) were calculated with ab‐initio relativistic wavefunction approaches. It is found that the core‐excited states probed by the XANES experiments, but not the ground states, exhibit φ ‐type covalent bonding or antibonding interactions.