Photophysics of phenyl-substituted polyacetylenes, theory

We present a theoretical study of the electronic structures of poly-phenyla cetylene (PPA) and poly-diphenylacetylene (PDPA). Strong photoluminescence (PL) in PDPA's is a consequence of the occurrence of the 2A(g) two-photon s tate above the optical 1B(u), in spite of the polyene backbone. This revers ed energy ordering las compared to linear polyenes and trans-polyacetylene, t-PA) is a signature of reduced effective electron correlations in PPA and PDPA. The optical gaps of the substituted materials are smaller than polye nes of the same chain length. (C) 2001 Elsevier Science B.V. All rights res erved.