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CPP: Chemische Physik und Polymerphysik

CPP 16: Electronic Structure and Spectroscopy II

CPP 16.9: Vortrag

Mittwoch, 29. März 2006, 16:45–17:00, ZEU 160

Optical absorption of various linear and cyclic thiophene based π-conjugated polymers — •Mariusz Bednarz and Peter Reineker — Abteilung Theoretische Physik, Universität Ulm, Albert-Einstein-Allee 11, 89069 Ulm, Germany

Recently, using thiophene based repeat units, the first series of fully conjugated macrocyclic structures: cyclo(thiophene-diacetylenes) and cyclo[n]thiophenes were synthesized (P. Bäuerle et al.). Such structures together with various series of linear oligothiophenes with controlled chain length exhibit an interesting relation between their absorption spectra. In particular, there is a clear relation between the peak position of the oligothiophenes and cyclothiophenes: the spectrum for the cyclothiphene with a given size corresponds to an oligotiophene chain of about half the length. The absorption spectra of such linear and cycliothiophenes show a systematic red shift with increasing number of thiophene units. In the present contribution, we will address an approach, based on the Frenkel exciton Hamiltonian, which describes the observed red shift tendency and the relationship between cyclothiophenes and corresponding oligothiophenes. Detailed study of the microscopic parameters depending on various side- and end-groups attached to the bare thiophene chains will be given. Also we show that cyclo(thiophene-diacetylenes) can be described as a fully conjugated system with very interesting manifestation of the cyclic symmetry as a Davydov components in the case of very small rings. It will be shown that diacetylene units embedded into thiophene cyclic structures can be described as another chromophor with larger π− transition than thiophene units itself.