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Photophysics and photochromism of Δ2,2' -BI-(2H-1,4-benzothiazine)

1986; Elsevier BV; Volume: 132; Issue: 2 Linguagem: Inglês

10.1016/0009-2614(86)80096-3

1873-4448

Ralph S. Becker, L. V. Natarajan,

Radical Photochemical Reactions

Δ2,2' -bi-(2H-1,4-benzothiazine) shows striking photochromism and thermochromism. The color change is thermally and photochemically reversible. The photochromism can be ascribed to the cis-trans isomerization about the central double bond, the yellow trans isomer being more stable. The quantum yield of formation øCP of the cis-benzothiazine from trans in dioxan was found to be 0.035 at 355 nm excitation. Laser flash photolysis of the trans-benzothiazine revealed that the excited singlet state of π, π* character is the originating state for the photochromism since there is no experimental evidence of a triplet intermediate.