Theoretical Investigation of Nonradiative Transitions in Polysiloles

Silacyclopentadienes, or siloles, exhibit aggregation-enhanced photoluminescence. Quenching of luminescent nano-aggregates by electron deficient nitroaromatic explosives, such as trinitrotoluene, may be monitored to detect explosives [1]. Detection relies on both electronic and structural interactions between the sensing material and the analyte. These interactions can be studied using state-of-the-art theoretical methods thus aiding the screening of potentially useful polymers. In particular, we consider 2,3,4,5-tetraphenylsiloles which have been shown experimentally to be only slightly luminescent as individual monomers in solution and highly luminescent when aggregated into oligomers [2]. Using density functional theory along with quasi-particle methods we investigate the electronic structure of the molecule and its luminescent properties. We consider the possibility that the relatively unhindered motion of the phenyl rings may provide a nonradiative transition channel. \newline \newline [1] H. Sohn, M. J. Sailor, D. Magde and W. C. Trogler, \textit{J. Am. Chem. Soc.} \textbf{125}, 3821 (2003). \newline [2] J. Luo, \textit{et. al.}, \textit{Chem. Communications}, 1740 (2001).