Table 2. Effect of the substitution on the reactive carbon atoms on the computed S₁ excited state for different derivatives of 2(oo). In addition to the wavelength (λ/nm) and oscillator strength (f), the localisation of the LUMO photochromic orbital is also given, together with the orbital composition of this transition.

	DTE with LUMO	λ	f	Composition of S1
2(oo)-a	Both	321	1.00	H → L (81%)
2(oo)-b	CN-substituted	350	0.83	H → L (79%)
2(oo)-c	Both	350	0.99	H → L (89%)
2(oo)-d	Me-substituted	330	1.00	H → L (58%)
				H → L + 1 (31%)
2(oo)-e	Both	302	0.77	H – 1 → L (30%)
				H → L + 1 (41%)
2(oo)-f	First DTE	363	0.16	H → L (78%)
	L + 1: second DTE	355	0.13	H → L + 1 (78%)
2(oo)-g	Both	351	0.28	H → L (67%)
2(oo)-h	CN-substituted	368	0.90	H → L (72%)