PHOTOCHROMIC AND THERMOCHROMIC SPIRANS 41*. QUANTUM-CHEMICAL STUDY OF THE GEOMETRY AND ELECTRONIC STRUCTURE OF 1,3,3-TRIMETHYL-1',2'-DIPHENYLSPIRO(INDOLINE- 2,7'-FURO(3,2-f)CHROMENE) IN THE GROUND AND EXCITED STATES

Quantum-chemical modeling of the geometry and electronic structure of the ground state and the lowest excited states of various multiplicity was undertaken for the photochromic compound 1,3,3-tri-methyl1',2'-diphenylspiro[indoline-2,7'-furo[3,2-f]chromene], which belongs to the spiropyran class. After analysis of the localization of electronic excitation in the molecule, it was suggested that the photoinduced transformation of the colorless spiro form to the colored merocyanine photoproduct takes place with great probability in its lowest singlet state and not in the triplet excited state.