97135-70-1

Upstream product

• 25565-20-2 trans-1-methyl-4-<4-nitrostyryl>-pyridinium iodide 

Relevant academic research and scientific papers

Charge transfer fluorescence of trans-stryrylpyridinium iodides

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.

The Role of Triplet States in the Trans - Cis Photoisomerization of Quaternary Salts of 4-Nitro-4'-azastilbene and Their Quinolinium Analogues. 6

The quantum yields of fluorescence (φf) and of trans -> cis photoisomerization (φt->c) were measured for quaternary salts of 4-nitro-4'-azastilbene derivatives (At+X-; At+ = trans-1-alkyl-4-pyridinium and quinolinium; X(1-) = I(1-), ClO4(1-), and CH3SO4(1-)) as a function of solvent polarity, temperature, and concentration of quenchers.Transients (lifetime ca. 200 ns at 25 deg C, λmax ca. 450 nm) observed by laser flash photolysis were identified as the trans triplet configuration of either the cation (3*At+) or the ion pair (3*At+...X-) in highly and less polar solvents, respectively.In polar solvents at room temperature 3*At+ is quenched by oxygen, azulene, ferrocene, and I(1-) at rates close to the diffusion-controlled limit.The quenching measurements under pulsed and steady-state conditions suggest that 3*At+ is an intermediate in the trans -> cis photoisomerization route.In contrast to the pyridinium salts, φt->c does not follow for the quinolinium salts linear Stern-Volmer dependences on , , or .It is concluded that for the pyridinium salts trans -> cis photoisomerization occurs only via the triplet mechanism, whereas a second route, bypassing the lowest triplet state, contributes to a certain extent (ca. 40percent) for the quinolinium salts (mixed singlet-triplet mechanism).