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), sp iro[1,3-dithiolane-2,2'-indan]-1',3'-dione (10), spiro[1,3-benzodioxol e-2,2'-indan]-1',3'-dione (11), hylspiro[1,3-benzodithiole-2,2'-indan] -1',3'-dione (12), and o[indan-2,2'-naphtho[2,3-d]-1,3-dioxole]-1,3-di one (13) have been prepared. Their He(I) photoelectron spectra and the ir UV/Vis spectra have been investigated. A comparison between the fir st PE bands of the spiro compounds and the corresponding fragments ind icates only a very weak interaction between both parts. The UV/Vis spe ctra 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 f rom the HOMO(pi), localized at the donor fragment, to the LUMO(pi) of the acceptor moiety (charge transfer). X-ray investigations of 8-10 a nd 13 show no interaction between the two perpendicularly arranged moi eties.