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Resonance raman studies of transient species in the photochromism of 1',3',3'-trimethylspiro-[2h-1-benzopyran-2,2'-indoline]

✍ Scribed by Hiroaki Takahashi; Keiichi Yoda; Hiroaki Isaka; Tomoyuki Ohzeki; Yoshiki Sakaino

Publisher: Elsevier Science
Year: 1987
Tongue: English
Weight: 472 KB
Volume: 140
Category: Article
ISSN: 0009-2614
DOI: 10.1016/0009-2614(87)80422-0

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✦ Synopsis

Resonance Raman spectra of transient species of 1 ',3',3'-trimethylspiro-[2H-l-benzopyran-2,2'-indoline] in various solvents reveal that at least four transients having merocyanine-like structures are involved in the photochromism of this compound. It is concluded that the transient species in aliphatic hydrocarbons involves the least polar TTC configuration (trans-trans-cis with respect to the three C-C partial double bonds in the merocyanine-like skeleton), while in polar solvents, CTT and CTC conligurations having larger dipole moments are more stable than TTC. In alcohols, the TTT and CTT configurations are stabilized by hydrogen bonding with solvent molecules. From the temperature dependence of the spectra, the energy difference between TTC and CTT configurations in acetonitrile is estimated to be 4.8 kJ mol-I.

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