Original scientific paper

Molecular Geometry and Electronic Structure of Heptalentropones and Heptalendiones

Giuseppe Buemi ; Dipartimento di Scienze Chimiche, Universita di Catania, Viale A. Doria 6, 95125 Catania, Italy
Felice Zuccarello ; Dipartimento di Scienze Chimiche, Universita di Catania, Viale A. Doria 6, 95125 Catania, Italy

Abstract

The molecular geometries of 8-H-cycloheptatropone (I), 8-H-
-cycloheptatropolone (II), 2-methoxy-8-H-cycloheptatropone (III),
heptalen-1,8-dione (IV), 7-methoxy-heptalen-1,8-dione (V), 9-methoxy- heptalen-1,8-dione (VI) were fully optimized at lVIINDOj3
level. Heptalen-2,3-dione was also taken into account. The electronic
structures of the above molecules were studied by means of INDOjS method and the importance of doubly excited configurations
was tested at CNDO/S level. In all compounds a remarkable »single« and »double« bond alternation was found. Hydroxy and methoxy substitution affects the geometry of the ring where the substitution occurs whilst the unsubstituted ring unđergoes minor 01' negligible changes. The electronic transitions agree well enough with the experimentally available absorption maxima; a strong transition is predicted in the neighborood of 200 nm. Several of these transitions
can be correlated with those of tropone and tropolone: on the whole they are not, 01' negligibly, affected by double excitations except those Iying in the range of 5 eV and the ones at 4.29 eV and 4.82 eV of heptalen-2,3-dione.

Keywords

Hrčak ID:

177302

URI

https://hrcak.srce.hr/177302

Publication date:

25.7.1986.

Visits: 802 *