Enhanced Photoluminescence from Group 14 Metalloles in Aggregated and Solid Solutions

The unusual photoluminescence characteristics of a series of six group 14 metalloles (1,1-dimethyl-2,3,4,5-tetraphenylmetalloles and 1,1-diphenyl-2,3,4,5-tetraphenylmetalloles) containing silicon, germanium, or tin have been
investigated. Although the compounds are weakly luminescent in dilute fluid solution at room temperature, they
undergo a substantial enhancement of photoluminescence when forced to aggregate, as in mixed solvent systems.
The compounds also exhibit considerable emission when incorporated into rigid room-temperature glasses of sucrose
octaacetate. Absorption and emission characteristics of the compounds, including luminescence quantum yields, in
fluid solution, solution-phase aggregates, and room-temperature glasses are reported. Quantum yields increase by
as much as 2 orders of magnitude in the aggregates and glasses, compared to fluid solution. Experimental evidence
supports the conclusion that the aggregation-induced enhancement of luminescence results from restricted
intramolecular rotations in the packed metalloles. The unusual aggregation-induced enhancement of these compounds
makes them potentially useful for the fabrication of a variety of electrooptical devices and sensors. In addition, the
X-ray crystal structure of hexaphenylgermole is reported.