Novel hetarylazo dyes containing tetrazole and hydroquinoline moieties: spectral characteristics, solvatochromism and photochemistry

Abstract

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 > HO > MeOH > ACN > CHCl) 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.

Rapid Generation of Tetrahydropyridines and Tetrahydroquinolines by Dearomative Cyanation/Grignard Addition

“…Peniprequinolone is a nematicidal alkaloid [6] . 2,2,4‐trimethyl‐8‐hydroxy‐THP is a specific reagent for photometric determination of iron (Ш) salts [7] and the key precursor to synthesize hetarylazo dyes [8] . 6‐Carboxylic acid‐THP is a calcium‐activated potassium channel (BKCa) agonist [9] …”

“…[6] 2,2,4-trimethyl-8-hydroxy-THP is a specific reagent for photometric determination of iron (Ш) salts [7] and the key precursor to synthesize hetarylazo dyes. [8] 6-Carboxylic acid-THP is a calcium-activated potassium channel (BKCa) agonist. [9] Previous approaches to 2,4-disubstituted THPs and THQs mainly rely on annulative chemistry.…”