We are currently investigating the photophysics of Coronene (Cor). According to the Weller-equation, symmetry-breaking charge separation (SB-CS), i.e. Cor* + Cor → Cor•+ + Cor•–, should not be operative with this molecule. Quantum mechanical calculations, on the other hand, indicate a significant driving for SB-CS in polar solvents.
The figure above (right) shows the merged fs-µs visible transient absorption (TA) spectrum of Cor in benzontrile upon excitation of the allowed S3 ← S0 band. The TA spectrum shows quick internal conversion (< 1 ps) to the S1 state (τ = 274 ns) before intersystem crossing to the T1 state (τ ≈ 12 µs) occurs. No indication of the ion features are evident in the TA data. Further systematic investigations with Cor and structurally similar molecules are planned to elucidate the molecular requirements for SB-CS to be operative.
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Contact:
Eric Vauthey
Physical Chemistry Department - Sciences II - University of Geneva
30, Quai Ernest Ansermet - CH-1211 Geneva 4 (Switzerland)
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