Fig. 3: Photophysical properties of thiophene belts.
a Ultraviolet–visible absorption and fluorescence spectra of the diluted dichloromethane solution of thiophene belts at room temperature (abs: solid lines, flu: dashed lines, green for 1 and blue for 2). The fluorescence quantum yield and lifetime are shown in the upper right corner. Phosphorescence spectra of thiophene belts in 2-methyltetrahydrofuran at 77 K upon excitation at 350 nm (long dashed lines, pink for 1 and orange for 2). The phosphorescence quantum yield and lifetime for 2 are shown in the upper right corner. b Structures and frontier molecular orbitals calculated at the B3LYP/6-31 G(d) level of theory with dispersion correction of Grimme’s D3 (isovalue: 0.02) of 1 (yellow square), cyclothiophene (left gray square), and cycloparaphenylene (right gray square) of the same ring-size as 1. Blue and red indicate negative and positive wave functions, respectively; HOMO, highest occupied molecular orbital; LUMO, lowest unoccupied molecular orbital. HOMO and LUMO of 1 reflect the fused structure of cyclothiophene and cycloparaphenylene.
