Abstract
AbstractAn azulenylosquaric dye (ASQ) has been synthesized to investigate its associated photophysical properties. ASQ is essentially nonluminescent (Φf < 3 × 10−;6) in any solvent despite its very high absorption extinction coefficient (760 nm, ε ˜ 8.2 × 104 M−;1cm−;1 in methanol). Femtosecond fluorescence upconversion, anisotropy kinetics and transient absorption experiments, in combination with the theoretical time‐dependent DFT approach, leads us to conclude that the 760 nm absorption is ascribed to the fully allowed S0 → Sn (n 2) transition. The observed < 130 fs decay component is attributed to the Sn → S1 internal conversion, while the S1 → S0, with a slower radiative decay time (> 233 ns) undergoes a dominant radiationless deactivation process (710 70 fs) possibly governed by strong interaction between S1 and S0 potential energy surfaces.
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