KAPIČKA, Libor, Pavel KUBÁČEK and Petr HOLUB. Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments. Journal of Molecular Structure (Theochem), Amsterdam: Elsevier Science, 2007, vol. 820, 1-3, p. 148-158. ISSN 0166-1280.
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Basic information
Original name Bonding and aromaticity of cyclic phosphazenes viewed as interaction of Dnh fragments
Authors KAPIČKA, Libor (203 Czech Republic), Pavel KUBÁČEK (203 Czech Republic, guarantor, belonging to the institution) and Petr HOLUB (203 Czech Republic, belonging to the institution).
Edition Journal of Molecular Structure (Theochem), Amsterdam, Elsevier Science, 2007, 0166-1280.
Other information
Original language English
Type of outcome Article in a journal
Field of Study 10403 Physical chemistry
Country of publisher Czech Republic
Confidentiality degree is not subject to a state or trade secret
WWW URL
Impact factor Impact factor: 1.112
RIV identification code RIV/00216224:14310/07:00032396
Organization unit Faculty of Science
UT WoS 000250354000022
Keywords in English Cyclic phosphazenes; Aromaticity; Orbital interactions; Potential energy surface
Tags aromaticity, Cyclic phosphazenes, Orbital interactions, potential energy surface
Tags International impact, Reviewed
Changed by Changed by: doc. RNDr. Petr Holub, Ph.D., učo 3248. Changed: 29/4/2020 21:48.
Abstract
The qualitative molecular orbital approach based on orbital interactions was used to explore the nature of bonding in cyclic fluorophosphazenes (F2PN)n, where n is 2-6. Besides the classical skeleton of sigma-bonds, only two, one radial and one axial, 2n-center two-electron pi-bonds significantly participate in the extra stabilization of the (PN)n ring. The pi-radial interaction is more effective and comparable by size with the sigma ones. Additional slight stabilization of a (PN)n ring is achieved by nonbonding pi-radial and pi-axial molecular orbitals (MOs) which are mainly localized on nitrogen atoms. The orbital interactions have a hyperconjugation character. The bonding energy decomposition analysis showed that the cyclic interactions are about half covalent and half electrostatic. The covalent bonding is dominated by radial interactions. The aromaticity concept is not appropriate for description of bonding in cyclophosphazenes. The contribution of phosphorus d atomic orbitals to the concept of chemical bonding in phosphazenes is negligible, but the inclusion of d phosphorus functions in a basis set is appropriate for a correct quantitative description of electronic and geometric structure. Extended Hückel (EHT), ab initio and density functional (DFT) calculations provide the same qualitative picture of the bonding. The very flat B3LYP/6-311+G(3df)//B3LYP/6-31G(3df) potential energy surface (PES) with the low energy barrier (1.6 kJ mol-1) indicates the very fast and easy conformational motion of (F2PN)4. The global minimum on this PES is the S4 conformation.
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