Chemistry of Vibronic Coupling, Part 4: Off-Diagonal Vibronic Coupling Constants Across the Periodic Table

• Autorzy: Grochala W. , Hoffmann R.
• Języki publikacji: EN

Abstrakty

EN

Vibronic coupling for inter–valence charge–transfer states in linear symmetric ABA molecules (A, B = s–, p– or d–block element) is investigated computationally. In particular we examine vibronic coupling as a function of the s, p, d – block nature of the A and B constituent elements. Based on density-functional theory computations for 395 triatomic molecules, we construct a map of a vibronic stability parameter G (defined as the ratio of asymmetric to symmetric stretching force constants) across the periodic table. Correlations of G versus the sum and difference of electronegativities of A and B elements are tested, and also vs. a useful parameter f, the ratio of the sum of electronegativities to an AB separation. Usually, the larger the sum of electronegativities, and the shorter the AB bond, the larger the vibronic instability. The largest vibronic instability thus occurs for interhalogen compounds. Molecules containing d-block elements exhibit trends similar to those of molecules built of p-block elements with similar electronegativities, although the latter are usually more unstable. A molecular orbital model is developed to explain the trends obtained in our computations, as well as to build a framework for systematic manipulation of vibronic coupling constants in molecular systems. From the model we argue that vibronic coupling is usually strongest in systems built of hard Lewis acids and bases.We also show that s–p mixing and “ionic/covalent curve crossing” increase the vibronic instability of a molecule. To attain high vibronic instability, one should build a molecule of light, highly electronegative p–block elements. These findings may be of use in the experimental search for new superconducting materials.

• Wydawca: Polskie Towarzystwo Chemiczne
• Czasopismo: Polish Journal of Chemistry
• Rocznik: 2001
• Tom: Vol. 75, nr 11
• Strony: 1603--1659
• Opis fizyczny: Bibliogr. 68 poz., rys.

Twórcy

autor

Grochala W.

autor

Hoffmann R.

• Department of Chemistry and Chemical Biology, Cornell University, Ithaca NY, 14853-1301 USA