Novel hetarylazo dyes containing tetrazole and hydroquinoline moieties: spectral characteristics, solvatochromism and photochemistryElectronic supplementary information (ESI) available. See DOI: 10.1039/c6pp00251j

• Main Authors: Nekipelova, Tatiana D, Khodot, Evgenii N, Klimovich (Lygo), Olga N, Kurkovskaya, Lidiya N, Levina, Irina I, Kuzmin, Vladimir A
• Format: Journal Article
• Language: English
• Published: 30.11.2016
• ISSN: 1474-905X; 1474-9092
• DOI: 10.1039/c6pp00251j

Novel hetarylazo dyes containing tetrazole and tetra- or dihydroquinoline moieties were synthesized and their spectral properties in solvents of different polarities and H-bonding abilities were examined. The dyes exhibit solvatochromism dramatically depending on the proton accepting ability of solvents: (DMSO > H 2 O > MeOH > ACN > CH 2 Cl 2 ) and the dye concentration. Upon dilution the absorption maximum of the visible band shows a blue shift and the absorption coefficient of the maximum decreases. This was accounted for by complex formation either between the dye molecules or between the dye and solvent molecules. The H-bond with partial proton transfer is formed between the acidic NH group of the tetrazole moiety of a dye molecule and the basic NH group of the hydroquinoline moiety of the other dye molecule or with a solvent with proton accepting ability. Upon dilution the equilibrium shifts to the complex with a solvent. The coexistence of several forms of the dye molecules with different absorption spectra was demonstrated in pulse photolysis upon excitation by light with different wavelengths. Three forms of cis -isomers were registered. The photogenerated cis -isomers decay with lifetimes from 200 μs to 5 ms. The fast cis - trans dark isomerization determines the photostability of the dyes. Novel hetarylazo dyes containing tetrazole and tetra- or dihydroquinoline moieties exhibit solvatochromism dramatically depending on the proton accepting ability of solvents and the dye concentration.