Theoretical and Experimental Study of New Photochromic Bis-Spiropyrans with Hydroxyethyl and Carboxyethyl Substituents

Table 4

Excitation energy 𝐸_ex (eV), corrected [17] excitation energy 𝐸_corr (eV) and oscillator strength 𝑓 of the first three singlet transitions of the merocyanine (2a)TTC-SP and (2a)TTC-TTC according to the TD DFT CPCM/PBE0/6-311G** calculation in toluene solution.

Structure	Transition	𝐸ex	𝐸corr	𝑓
(2a)TTC-SP	S0-S1	2.332	2.077	0.5305
	S0-S2	2.821	2.533	0.0021
	S0-S3	3.184	2.871	0.6352
(2a)TTC-TTC	S0-S1	2.828	2.539	0.6767
	S0-S2	2.869	2.578	1.1975
	S0-S3	2.990	2.691	0.1199