Absorption, emission and photoisomerization of a protonated stilbazolium betaine in solution and micelles

• Published in: Colloids and surfaces. A, Physicochemical and engineering aspects Physicochemical and engineering aspects, 1994-03, Vol.83 (1), p.83-87
• Main Author: Abdel-Halim, Shakir T.
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; Chemistry; Emission spectroscopy; Exact sciences and technology; General and physical chemistry; Micelles; Photochemistry; Photoisomerization; Physical chemistry of induced reactions (with radiations, particles and ultrasonics); Stilbazolium betaine
• ISSN: 0927-7757; 1873-4359
• DOI: 10.1016/0927-7757(93)02641-Q

This paper reports on the absorption and fluorescence maxima and photoisomerization quantum yield of 2-(4-hydroxystyryl)-1-methylpyridinium betaine (MH +). In neat polar protic and aprotic solvents, the absorption energy and fluorescence energy vary rectilinearly with the hydrogen bond acceptor ability β and Taft's solvent polarity parameter π* respectively. A specific hydrogen bonding interaction between MH + as a proton donor molecule and the micelle surface of the anionic sodium dodecyl sulphate (SDS) surfactant was proposed as an efficient hydrogen acceptor. Micelles have decreased the photostability of the cis form by decreasing the percentage cis value at the photostationary state and enhancing the photochemical cis—trans isomerization yield φ ct over the photostability in pure water. The MH + molecule deprotonates in the excited state as a weak acid in SDS micelles and the isomerization represents the main channel of deactivation while it deprotonates as a much stronger acid in cationic micelles of cetylpyridinium chloride (CPC) and cetyltrimethylammonium bromide (CTAB), and the isomerization is considered in this case to be a side channel of the deactivation.