Direct Observation of a Charge-Transfer State Preceding High-Yield Singlet Fission in Terrylenediimide Thin Films

Singlet exciton fission (SF) in organic chromophore assemblies results in the conversion of one singlet exciton (S₁) into two triplet excitons (T₁), provided that the overall process is exoergic, i.e., <i>E</i>(S₁) > 2<i>E</i>(T₁). We report on SF in thin polycrystalline films of two terrylene-3,4:11,12-bis­(dicarboximide) (TDI) derivatives <b>1</b> and <b>2</b>, which crystallize into two distinct π-stacked structures. Femtosecond transient absorption spectroscopy (fsTA) reveals a charge-transfer state preceding a 190% T₁ yield in films of <b>1</b>, where the π-stacked TDI molecules are rotated by 23° along an axis perpendicular to their π systems. In contrast, when the TDI molecules are slip-stacked along their N–N axes in films of <b>2</b>, fsTA shows excimer formation, followed by a 50% T₁ yield

Direct Observation of a Charge-Transfer State Preceding High-Yield Singlet Fission in Terrylenediimide Thin Films

Singlet exciton fission (SF) in organic chromophore assemblies results in the conversion of one singlet exciton (S₁) into two triplet excitons (T₁), provided that the overall process is exoergic, i.e., <i>E</i>(S₁) > 2<i>E</i>(T₁). We report on SF in thin polycrystalline films of two terrylene-3,4:11,12-bis­(dicarboximide) (TDI) derivatives <b>1</b> and <b>2</b>, which crystallize into two distinct π-stacked structures. Femtosecond transient absorption spectroscopy (fsTA) reveals a charge-transfer state preceding a 190% T₁ yield in films of <b>1</b>, where the π-stacked TDI molecules are rotated by 23° along an axis perpendicular to their π systems. In contrast, when the TDI molecules are slip-stacked along their N–N axes in films of <b>2</b>, fsTA shows excimer formation, followed by a 50% T₁ yield

Direct Observation of a Charge-Transfer State Preceding High-Yield Singlet Fission in Terrylenediimide Thin Films

Singlet exciton fission (SF) in organic chromophore assemblies results in the conversion of one singlet exciton (S₁) into two triplet excitons (T₁), provided that the overall process is exoergic, i.e., <i>E</i>(S₁) > 2<i>E</i>(T₁). We report on SF in thin polycrystalline films of two terrylene-3,4:11,12-bis­(dicarboximide) (TDI) derivatives <b>1</b> and <b>2</b>, which crystallize into two distinct π-stacked structures. Femtosecond transient absorption spectroscopy (fsTA) reveals a charge-transfer state preceding a 190% T₁ yield in films of <b>1</b>, where the π-stacked TDI molecules are rotated by 23° along an axis perpendicular to their π systems. In contrast, when the TDI molecules are slip-stacked along their N–N axes in films of <b>2</b>, fsTA shows excimer formation, followed by a 50% T₁ yield