Über Polyarylenalkenylene und Polyheteroarylenalkenylene, 7. Die Anwendung von HMO-Rechnungen auf elektronenspektroskopische und struckturanalytische Probleme oligomerer und polymerer Polyarylenalkenylene und Polyheteroarylenalkenylene

For the homologous series of the di-2-thienyl- and diphenylalkapolyenes with one to six olefinic double bonds and the oligomeric arylene- respectively 2,5-thienylenevinylenes and 2,5-thienylene-1,3-butadienylenes we have calculated by the HMO method the energy values of π → π^* transition (Δx_j values), which are in good agreement with the λ_max values (π → π^* transitions). We have also calculated the bond orders for the carbon-carbon bonds of all of these compounds. From the calculated bond orders one can see, that the adaptation of the bonds is reached for the tetramers or pentamers. The bond lengths of 5 simple oligomers-estimated by X-ray diffraction patterns-are in good agreement with the calculated bond orders corresponding to the adaptation of their bonds in such conjugated π-electron systems.