THROUGH-BOND AND THROUGH-SPACE INTERACTIONS IN OLIGO-ALKOXYTHIOPHENES- A SPECTROSCOPIC STUDY

The aim of this work is to understand the molecular structural propert ies which may justify the great observed stability of doped alkoxy pol ythiophenes. Infrared frequency and intensity spectroscopy and Raman s pectroscopy are used as probes. Suitably synthesized oligomers with in creasing chain length and preassigned chemical structure have been stu died together with several model molecules. The existence of through-s pace and through-bond S---O interactions has been revealed. The extent of the topologically dependent perturbation induced by the charge inj ection by the oxygen atoms is detected and measured. The inter- and in traring delocalizations have been monitored by the observation of the softening of the strongly Raman active ''amplitude mode'' and by the r ed shift of the electronic spectra. The conformation of the side chain s is trans planar in the solid state and collapses in a liquidlike pre melting state before the melting of the crystal. (C) 1996 American Ins titute of Physics.