Chemistry Weekly Seminar - Dr. Ron Steer
Dr. Ron Steer, Professor Emeritus in the Department of Chemistry, will present a seminar at 1:30 p.m. in Thorvaldson 110.
Title:
Chasing Upper State Singlet Fission:
A Tale of Observed Spectroscopy and Unobserved Photophysics in Azulene Derivatives, Aggregates and Multimers
Abstract:
Singlet fission (SF) is a photophysical process by which two triplet states are derived from one singlet excited electronic state in a chromophoric dimer, multimer or aggregate. In this talk I will briefly review the unusual electronic spectroscopy and photophysics of monomeric azulene and its simple derivatives. This information will then be used as a basis for commenting on the interesting lack of experimental photophysical data on azulene's known aggregates, dimers and multimers when excited to their second excited singlet (S2) states. Arguments will be presented that SF can occur generally from the S2 states of all dichromophoric systems that exhibit triplet-triplet annihilation and, by chemical substitution, can meet the SF energy requirement. The existing lack of S2 photophysical information from known di- or multi-azulene materials may thus be the result of an unrecognized ultrafast SF process. Novel azulene-based species that will offer the S2 singlet fission route of excited state relaxation will be identified. New experimental data on one such species will be presented.