Species λflu f Assignment 1 401 0.76 HOMO→ LUMO+1 (0.55) HOMO-1→ LUMO (-0.43) 2 399 0.83 HOMO→ LUMO+1 (-0.49) HOMO-1→ LUMO (0.49) 3 406 0.52 HOMO-1→ LUMO (0.67) HOMO-2→ LUMO (0.14) 4 428 0.59 HOMO→ LUMO+4 (0.47) HOMO→ LUMO+3 (0.34) 5 409 0.70 HOMO→ LUMO+5 (0.56) HOMO-1→ LUMO (-0.40) 6 454 0.50 HOMO → LUMO+1 (-0.41) HOMO-1→ LUMO (0.67) Expa 426

a Experimental data for 1 in chloroform [25].

Table 3: The fluorescence wavelengths λflu(in nm), the oscillator strength f, and main assignments (coefficient) of 1–6 in chloroform obtained at the TD-B3LYP/6- 31G(d,p)//TD-B3LYP/6-31G(d,p) level, along with available experimental data.