Efficient One-Pot Three-Component Synthesis of Monomethine Cyanine Dyes with Quinoline Nucleus and Their Spectral Properties

Abstract

An improved method for the preparation of monomethine cyanine dyes with quinoline nucleus by one-pot three-component using 1-methyl-2-quinolinethione, quaternized 2-or 4-methylheterocyclic compounds and methyl p-toluenesulfonate as starting materials was described. Compared with the traditional methods, the new synthetic method reduced the reaction steps, shortened the reaction time, avoided the separation and purification of the intermediate and reduced cost. The dyes absorbed in the region 478.0-563.0 nm and had molar extinction coefficients of 1.3 × 10 4 -9.4 × 10 4 L mol. Their fluorescence maxima and Stokes shifts were in the range of 525.2-594.4 nm and 16.2-80.6 nm in different solvents, respectively. From the spectral properties of the dyes in different solvents, it could be found that the λ max of the dyes were shorter in protonic solvents, and showed hypsochromic shifts with the increase of polarity of the solvents.

Spontaneous Aerobic Oxidation of 1,1,2,2-Tetrakis(N-methylpyridin- 4-ium)ethane Iodide to the Alkene and the Epoxide

“…Double deprotonation of structurally similar cyanine dimers by water leading to the increased π-conjugation was reported in the literature. , High air sensitivity of conjugated polymethylene dihydropyridines and cyanine dyes is also known. − The fact that 1′ is not observed in the NMR spectra but detected in the UV–Vis measurements is due to its low concentration and very high molar absorptivity typical for conjugated dihydropyridines and cyanine dyes (∼10 4 –10 5 M –1 ·cm –1 ; see the Supporting Information). − Electron transfer (SET) from a strong electron donor such as 1′ to molecular oxygen results in the formation of the superoxide anion radical, which is then able to couple with the parent radical cation molecule to give an alkyl peroxide . The corresponding alkyl hydroperoxide 1″ intermediate can undergo two different transformations yielding 2 and 3 simultaneously (Scheme , blue and red arrows).…”