DONOR-ACCEPTOR SPIRO-COMPOUNDS - SYNTHESES, STRUCTURES, AND ELECTRONIC-PROPERTIES

The six donor-acceptor spiro compounds spiro[1,3-dioxolane-2,2'-indan]-1',3'-dione (8), spiro[indan-2,2'-[1,3]oxathiolane]-1,3-dione (9), spiro[1,3-dithiolane-2,2'-indan]-1',3'-dione (10), spiro[1,3-benzodioxole-2,2'-indan]-1',3'-dione (11), 5-methylspiro[1,3-benzodithiole-2,2'-indan]-1',3'-dione (12), and spiro[indan-2,2'-naphtho[2,3-d]-1,3-dioxole]-1,3-dione (13) have been prepared. Their He(I) photoelectron spectra and their UV/Vis spectra have been investigated. A comparison between the first PE bands of the spiro compounds and the corresponding fragments indicates only a very weak interaction between both parts. The UV/Vis spectra of 11-13 show a moderate long-wavelength shift of the first band as compared to 1,3-indandione. This band is assigned to a transition from the HOMO(pi), localized at the donor fragment, to the LUMO(pi*) of the acceptor moiety (charge transfer). X-ray investigations of 8-10 and 13 show no interaction between the two perpendicularly arranged moieties.