Table 3. Excitation Energies at Different Levels of Theory in Gas Phase.

Level of Theorya	Transition Energy
TD/B3LYP/jun-cc-pVDZ83	2.4696 eV (502.04 nm)
TD/B3LYP/jul-cc-pVDZ	2.4619 eV (503.62 nm)
TD/B3LYP/6-311G(d)	2.4871 eV (498.51 nm)
TD/B3LYP/jun-cc-pVTZ	2.4821 eV (499.52 nm)
TD/B3LYP/jul-cc-pVTZ	2.4837 eV (499.19 nm)
TD/CAM-B3LYP/jun-cc-pVDZ	2.6724 eV (463.95 nm)
TD/CAM-B3LYP/jul-cc-pVDZ	2.6632 eV (465.55 nm)
TD/CAM-B3LYP/jun-cc-pVTZ	2.6843 eV (461.89 nm)
TD/CAM-B3LYP/jul-cc-pVTZ	2.6858 eV (461.63 nm)
Cis(d)/B2PLYP/jun-cc-pVDZ	2.6102 eV (475.00 nm)
Cis(d)/B2PLYP/jul-cc-pVDZ	2.5911 eV (478.50 nm)
Cis(d)/B2PLYP/jun-cc-pVTZ	2.6074 eV (475.52 nm)
Cis(d)/B2PLYP/jul-cc-pVTZ	2.6075 eV (475.49 nm)
Experimental	2.59 eV (478 nm)

^aIn all calculations empirical dispersion (D3BJ)⁸⁴ has been employed.