. 2023 Mar 20;14(14):3873–3880. doi: 10.1039/d3sc00345k

The first vertical excitation energies (in eV) calculated at the CC2/def2-TZVP level of theory. Contributions from doubly excited configurations to the wavefunction of the S₁ and T₁ states, and the obtained singlet–triplet gap (in eV) for molecules 1–4 are given.

Molecule	Irrep^a	E(S₁ ← S₀) (%D)		E(T₁ ← S₀) (%D)		ΔE_ST
1	a′′	2.677	(13.22)	2.877	(12.24)	−0.200
2	a′′	2.676	(13.18)	2.876	(12.16)	−0.200
3	a	2.588	(13.30)	2.786	(12.29)	−0.198
4	a	2.659	(13.18)	2.854	(12.24)	−0.195

Irreducible representation.

The first vertical excitation energies (in eV) calculated at the CC2/def2-TZVP level of theory. Contributions from doubly excited configurations to the wavefunction of the S1 and T1 states, and the obtained singlet–triplet gap (in eV) for molecules 1–4 are given.