95495-32-2Relevant academic research and scientific papers
Photoinduced Electron Transfer vs. Trans -> Cis Photoisomerization of Quaternary Salts of 4-Substituted 4'-Azastilbenes (R = CN, H, CH3, and OCH3) and Their Quinolinium Analogues.
Goerner, Helmut
, p. 1887 - 1894 (1987)
A series of quaternary salts of trans-1-alkyl-4-pyridinium and -quinolinium (At+X-; R = CN, H, CH3, and OCH3, X- = I- and ClO4-) were studied in solution by using steady-state irradiation and pulse excitation methods.A transient, observed by pulse radiolysis (iodide or perchlorate) and laser flash photolysis (248 nm; iodide only) in polar solvents, is assigned to the radical A, formed by one-electron reduction of At+.A radical was also produced by laser excitation (353 nm) of At+ in the presence of electron donors (D: I-, SCN-, and amines, e.g.DABCO, triethylamine, and dimethylaniline) at high concentrations.The quantum yield of trans -> cis photoisomerization (Φt->c) decreases on increasing and the yield of A radical shows the corresponding increasing dependence.On direct excitation of At+ the electron-transfer process occurs mainly via static fluorescence quenching and on sensitized excitation via dynamic triplet quenching.In solvents of moderate polarity (e.g. dichloromethane) where the salts are present as ion pairs, Φt->c is stongly reduced for the iodides as compared to the perchlorates.Photoinduced electron transfer and trans -> cis photoisomerization via the singlet mechanism are competing processes also for the ion pair.At lower temperatures the yield of formation of A radical is reduced and Φt->c correspondingly enhanced.
Charge transfer fluorescence of trans-stryrylpyridinium iodides
G?rner, Helmut
experimental part, p. 199 - 203 (2012/01/13)
The photoprocesses of trans-1-methyl-4-[4-R-styryl]pyridinium iodide (R = H, P1) and derivatives with a cyano, a nitro and a methoxy group at the phenyl moiety, P2-P4, respectively, were studied in solution. In solvents of relatively low polarity, e.g. tetrahydrofuran, where contact ion pairs are present, the fluorescence spectrum of the styrylpyridinium is significantly red-shifted and the quantum yield is strongly enhanced. These findings are due to photoinduced electron transfer from I- to the excited singlet state of the cation. The features of complementary trans-styrylquinolinium iodides are in good accordance.
