Table 1.

Bond energies (∆E in kcal/mol) of neutral quartets (ZORA-BLYP-D3/QZ4P), either in a relaxed structure (C₂ symmetry) or constrained to planarity (C_2h symmetry)

Quartet	C2 symmetry		C2h symmetry
	∆E (gas phase)	∆E (water)	∆E (gas phase)	∆E (water)
(I)2	− 45.8	− 15.2	− 42.6	− 9.3
(I′)2	− 54.0	− 18.7	− 52.2	− 16.5
(I″)2	− 51.9	− 18.5	− 51.3	− 17.5
(II)2	n.d.	− 14.4	n.d.	− 7.3
(II′)2	− 50.1	− 17.6	− 46.3	− 13.7

Selected geometrical parameters of the quartets are provided in Table S1