Sulphur Heterocycles Bridged by a Single Bond

According to PPP calculations the excitation energies of the bithienyls depend little on the conformational arrangement. The blue shift observed for the 2,3 - and 3,3 -isomers relative to the 2,2 -isomer, and reproduced by 

In the absorption spectrum of quinquethienyl (118) one observes a hypsochromic shift in solution and in a monolayer. Theoretical calculations based on the electron-gas model and an oscillator model have established the polymeric card-model proposed earlier.  

The energy gaps for 33 macromolecules, among them (119), have been investigated by the Huckel one-electron approximation.  

---