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When excited with large excess of energy over the lowest excited singlet state, two alkyl derivatives of dibenzo[cde, mno]porphycene undergo rapid relaxation to S₁. The S₁ depopulation occurs in 10–20ps, leading directly to S₀. The relaxation rates are only weakly temperature or medium-dependent. This behavior contrasts with properties of parent porphycene, where the relaxation is much slower in argon matrices: after excitation into S₃/S₄, it takes about 100ps to reach S₁, which then decays in 15ns. The differences are explained by the planarity and rigidity of parent porphycene, as opposed to nonplanar, flexible structure of dibenzo derivatives.