. Author manuscript; available in PMC: 2020 Oct 30.

Published in final edited form as: J Am Chem Soc. 2019 Oct 17;141(43):17287–17294. doi: 10.1021/jacs.9b08711

Table 2.

Relative energies (ΔE in kcal mol⁻¹), including barriers for ring inversion (racemization) for 1-D₂, 1-C_2h and the corresponding radical cations and diradical dications at the (U)B3LYP/6–31G(d)+ZPVE level of theory.

Crit. point	Structure	State	ΔE	ΔE_ST^a
minima	1-C_2h	¹A_g	0.00	-
minima	1-D₂	¹A	1.08	-
TS	1-C₁	¹A	43.12	-
minima	1^•+-C_2h	²A_g	0.00	-
minima	1^•+-D₂	²B₃	0.14	-
TS	1^•+-C₁	²A	38.14	-
minima	1^2•2+-D₂	³B₃	0.00 (0.00)^b	0.00
	1^2•2+-D₂	BS	-	0.59
	1^2•2+-C_2h	³A_u	0.51 (–0.01)^b	0.00
	1^2•2+-C_2h	BS	-	0.95
TS	1^2•2+-C₁	³A	35.61 (38.19)^b	0.00
TS	1^2•2+-C₁	BS	-	0.81

Singlet-triplet energy gaps (ΔE_ST in kcal mol⁻¹) for diradical dications; BS corresponds to a broken-symmetry singlet.

Values in parentheses are for triplet states of simplified 1b^2•2+ at the ROMP2/6–31G(d)//UB3LYP/6–31G(d) level of theory.