Table 3. The vertical excitation energies (ΔE in eV and nm) and oscillator strengths (f in a.u.) of 1a for the low-lying ππ* states at (S₀)_min ^a .

	TD-DFT (CAM-B3LYP)				CASPT2
State	ΔE (eV)	ΔE (nm)	f	Transition	ΔE (eV)	ΔE (nm)	f	Transition
1	4.79	259	0.262	5π → 1π*	4.33	286	0.213	5π → 1π*
2	5.33	232	0.052	5π → 2π*	4.43	280	0.250	5π → 2π*
3	5.49	225	0.010	5π → 3π*	5.53	224	0.384	4π → 1π*

^aThe main orbital transition is also shown.