A New Approach for Studying Bond Rupture/Closure of a Spiro Benzopyran Photochromic Material: Reactivity Descriptors Derived from Frontier Orbitals and DFT Computed Electrostatic Potential Energy Surface Maps

Table 1

HOMO/LUMO energies, chemical potential, hardness, and softness of SP/MC isomers.

Reactivity indices calculated from HOMO/LUMO energies (a.u.)	SP closed form			Merocyanine-like isomers
	Gas-phase	Toluene	EtOH	CCC	TTC	TTT
	−0.07782	−0.08822	−0.08812	−0.10667	−0.10023	−0.10994
	−0.19082	−0.1925	−0.19290	−0.19487	−0.19139	−0.19217
	−0.1343	−0.1404	−0.1405	−0.15077	−0.14581	−0.15101
	+0.1130	+0.1044	+0.1047	+0.0882	+0.09116	+0.08223
, (a.u.)^−1	8.8496	9.5785	9.5511	11.3379	10.9697	12.1610