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Theoretical Study of Thorium and Uranium Tetracarbide Molecules
Author(s) -
Pogány Peter,
Kovács Attila,
Konings Rudy J. M.
Publication year - 2014
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.201301425
Subject(s) - chemistry , complete active space , electronic structure , density functional theory , basis set , computational chemistry , molecular orbital , ground state , valence (chemistry) , configuration interaction , open shell , bond length , molecule , relativistic quantum chemistry , molecular geometry , ligand field theory , atomic physics , crystallography , crystal structure , ion , physics , organic chemistry
The electronic structure and ground‐state molecular properties of neutral Th and U tetracarbides were investigated by relativistic multireference calculations using complete active space self‐consistent field/multiconfiguration second‐order perturbation theory (CASSCF/CASPT2) with an all‐electron basis set as well as by density functional theory (B3LYP) in conjunction with relativistic pseudopotentials. The former calculations were extended with complete active space state interaction (CASSI) calculations accounting for spin–orbit coupling. The four carbon atoms can be arranged in various forms around the actinide atom to result in ten structural isomers found altogether in our study. The electronic ground state in both molecules corresponds to a planar fan‐type structure of C 2 v symmetry, in which the actinide atom is connected to a bent C 4 moiety. Three structures arise from various arrangements of C 2 moieties around the Th and U, whereas six isomers contain a C 3 moiety and a lone C bonded to the actinide. The latter CAnC 3 ‐type structures are very high‐energy structures (over 200 kJ mol –1 with respect to the ground state). The bonding characteristics in the most relevant structures were analysed on the basis of the valence molecular orbitals and the natural bond orbital method. We evaluated and interpreted the vibrational and electronic spectra. The present computed data for UC 4 suggest a revision of the assignment of a previously observed IR absorption band to a different isomer.