Synthesis And Spectral Property Of Novel Substituted 10h-pyrido "1,2-a" Indolium Perchlorates

Substituted 10H-pyrido[1,2-a]indolium perchlorates can be used as photosensitive dyes, fluorescent whiteners and organic light-guide sensitizers. On the basis of the study of synthesis and spectral property about many compounds of this series, it is found that the conjugated substituents introduced at 8-position make the maximum absorption(λ_max) and maxium emission(λ_em) red shift significantly. To obtain the compound with a largerλ_max andλ_em, herein, we introduced furan, thiophene, indole, N-ethylcarbazole with stronger electron-donating conjugation capability into 8-position and synthesized the target compounds. In view of this, ten of novel substituted 10H-pyrido[1,2-a]indolium perchlorates were designed and synthesized, and their spectral properties were investigated. Main work and results were listed as follows:1. Ten novel 8-heterocyclic vinyl-10,10-dimethyl-10H-pyrido[1,2-a]indolium perchlorates (1a¹c, 2a²e, 3a³b) were synthesized by phenylhydrazine and 3-methylbutanone (starting materials) in multi-steps. Structures of target compounds were confirmed by ¹H NMR, IR and elemental analysis.2. Compounds 2a²c were characterized and analyzed by X-ray diffraction. Crystal Structure analysis indicated that the moleculars of 2a²c were coplanar, respectively, meanwhile, there was a larger conjugated system in 2b and 2c owing to the introduction of phenyl and tolyl group.3. The UV-vis spectrum of ten target compounds were investigated. The results indicated that, with the electron-donating conjugation capability of the substituting group in 8-position being enhanced in each series, the maximum absorption(λ_max² in 1a¹c, 2b²e;λ_max³ in 2a, 3a;λ_max⁴ in 3b) of 1a¹c, 2a²e, 3a³b had a red-shift, while they red shifted 94.5 nm, 108.5 nm, 100.5 nm in maximum, respectively, in comparison with 8-styryl analog. The absorption bands in UV-Vis spectrum of the ten title compounds were also allocated.4. The fluorencence spectrum of ten target compounds were investigated. The results indicated that, with the electron-donating conjugation capability of the substituting group in 8-position being enhanced in each series, the maxium emission(λ_em) of 1a¹c, 2a²d, 3a³b had a red-shift, and the fluorescence intensity was also increasing;λ_em of 2e was between 2b and 2c, while the fluorescence intensity was strongest in 2a²e.λ_em of 1a¹c, 2a²d, 3a³b red shifted 111.0 nm, 145.0 nm, 152.0 nm in maximum, respectively, in comparison with 8-styryl analog. The fluorencence quantum yield of 1a¹c,2a²e was small, which was between 0.044 and 0.069, however, the fluorencence quantum yield 3a and 3b were 0.106 and 0.228, respectively. It indicated that 3a and 3b can be used as fluorescent acridine compounds, and have a certain application value in analysis.5. The absorbtion and emission spectrum in methanol, ethanol, acetonitrile, DMF were studied. The solvent had no obvious effects on the absorbtion spectrum of 1a¹c, 2a²e and 3b. However, the maximum absorption (λ_max³) of 3a in methanol, ethanol and DMF red shifted 21.0 nm, 12.5 nm and 10.5 nm in comparison with 3a in acetonitrile, respectively. The solvent had no obvious effects on the emission spectrum of ten target compounds.