Photophysics and photochemistry of positionally isomeric 1,2-dianthryltetramethyldisilanes: Investigation of anthryl–anthryl and anthryl–SiSi interactions

Aryldisilanes composed of one or two anthryl groups and tetra- or pentamethyldisilane chain units were prepared. The substitution of disilanes on the two anthryl groups was isomeric at positions 1, 2, and 9 for 1A2S2, 2A2S2, and 9A2S2, respectively. The photochemical properties of these compounds, such as absorption and fluorescence, were studied in solution. The dependence of the intramolecular π–π and σ–π interactions on the substitution position of the anthryl group were examined. The dianthryldisilanes displayed excimer emission as well as monomer emission. The emission characteristics of the dianthryldisilanes were compared with those of the corresponding anthrylpentamethyldisilanes (1AS2Me, 2AS2Me, and 9AS2Me). We also examined the time dependence of the fluorescence in view of the calculated potential energy surface of conformers in the ground state. The time constants correspond to the relaxation from the Franck–Condon structures those are most stable in the ground state to the relaxed excimer structures in the S1 excited state.