2J(SeSe) couplings in diseleno-substituted alkenylic compounds. A CLOPPA-IPPP analysis

• Published in: Journal of magnetic resonance (1969) 1990-04, Vol.87 (2), p.209-219
• Main Authors: Cavasotto, C.N, Giribet, C.G, de Azúa, M.C.Ruiz, Contreras, R.H, Pérez, J.E
• Format: Article
• Language: English
• Subjects: Atomic and molecular physics; Exact sciences and technology; Molecular properties and interactions with photons; Nuclear resonance and relaxation; Physics
• ISSN: 0022-2364; 1557-8968
• DOI: 10.1016/0022-2364(90)90001-P

A CLOPPA-IPPP analysis of 2 J(SeSe) couplings in two cyclic diseleno-substituted alkenylic compounds is performed. The total FC, PSO, DSO, and SD components of these couplings are evaluated within the RPA-INDO approximation, and total values are compared to the experimental values. The PSO interaction yields large values in both cases. Particularly, it is the dominant interaction in the cyclic plane compound. For this case, an analysis of the main transmission mechanisms of the SO term is performed in terms of localized molecular orbitals (LMOs) representing chemical functions. It is seen that the coupling is mainly transmitted by the occupied and vacant LMOs associated with the Se atoms. The influence of the π-type Se lone pairs is negligible, while the inplane Se lone pairs play an important role. Additivity of pathways is also analyzed: a “direct” and an “indirect” nonadditivity of paths are defined. A high direct nonadditivity is observed. A curious influence of the occupied π vinylic MO in the indirect nonadditivity is shown. Even though it is known that in several geminal couplings the DSO term yields an important contribution, it has a value of only about 10 −2 Hz in the present case.