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A multiconfigurational molecular orbital study of N ‐methyl oxatriazole
Author(s) -
Jones L. F.,
Shillady D. D.,
Duong A.,
Kier L. B.
Publication year - 2009
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.560360848
Subject(s) - chemistry , molecular orbital , slater type orbital , dipole , ab initio , atomic orbital , antibonding molecular orbital , delocalized electron , sydnone , configuration interaction , non bonding orbital , atomic physics , computational chemistry , mesoionic , wave function , complete active space , ground state , molecule , molecular orbital theory , electron , physics , ring (chemistry) , quantum mechanics , organic chemistry , medicinal chemistry
Abstract A multiconfigurational molecular orbital analysis has been carried out for a representative of a class of compounds found to have hypotensive activity in biological systems. N ‐methyl oxatriazole is a mesoionic compound isoelectronic with N ‐methyl sydnone and is found to be a highly polar, delocalized heterocyclic pi‐electron system. A pair‐excitation multiconfiguration self‐consistent field (PEMCSCF) treatment of the three lowest states indicates substantial mixing of the lowest unoccupied orbital with the ground state. Orthonormal resonance analysis shows how the orbital mixing improves the description of the dipole moment in the ground state. The PEMCSCF calculation was carried out using a minimum basis of Slater–Transform–Preuss functions fitted by six Cartesian Gaussian orbitals (STP‐6G) which were previously optimized on smaller molecules to yield energies below 4–31G values. This PEMCSCF calculation is one of the first applications of ab initio MCSCF techniques to a molecule of 10 atoms and represents development of practical methods for PEMCSCF treatment of up to 15 atoms.