Photophysical properties of the ITI photoswitches with a fluorine or chlorine-substituted aromatic ring^a.

	λ max,Z (nm)	λ max,E (nm)	Φ Z–E (%)	ε Z (M−1 cm−1)	ΔG°# (kcal mol−1) calc.	ΔG°# (kcal mol−1) exp.	t 1/2 (ms)
1v	421	515	4.8	2100	14.8	15.9	83.3
1x	424	517	4.6	2400	14.5	15.8	70.1
1y	438	541	0.047	4000	13.2	15.2	26.5
1z	423	510	1.1	2000	15.4	16.3	157.6
1α	425	523	5.7	1800	14.6	16.0	104.8
1β	410	505	7.6	600	14.9	14.4	6.3

^aShifts of λ_max, quantum yields, extinction coefficients for the Z- and E-isomers of ITIs 1v-β in MeOH. Experimental λ_max,E values are obtained from TA. Theoretical activation barriers for thermal relaxation were derived at the M06-2X/6-31+G(d)//6-311++G(2df, 2p) level. Experimental activation energies were calculated with the Eyring equation (with κ = 1). Thermal relaxation rates of ITIs 1v-β were recorded in MeOH. Experimental half-lives were obtained from ns TA spectroscopy.