Synthesis, DFT calculations and cyclic voltammetry analysis of new heterocyclic green dyes: 2-(5-Hydroxyimino-1-alkyl-4,5-dihydro-1H-4-indazolyliden)-2-arylacetonitriles

•A facile method to synthesis of new heterocyclic green dyes is presented.•The spectral and photophysical properties of these compounds are investigated.•Solvent effects on absorption spectra of these dyes are studied.•DFT calculations of one structure and cyclic voltammetry analysis are also performed.

New derivatives of 2-(5-hydroxyimino-1-alkyl-4,5-dihydro-1H-4-indazolyliden)-2-arylacetonitriles were synthesized by the reaction of 1-alkyl-5-nitro-1H-indazole with different arylacetonitriles via nucleophilic substitution of hydrogen. The structures of all newly synthesized compounds were confirmed by IR, 1H NMR, 13C NMR and Mass spectral data. The compounds were deep green in color and their color intensity indicates intramolecular charge transfer (ICT) states from the donor site (OH group) to the acceptor moiety (CN group). The absorption spectra of these dyes are similar to each other and the values of extinction coefficient for them are too large. Solvent effects on absorption spectra of these dyes have been studied and the absorption band in protic solvents undergoes a bathochromic shift. Density function theory (DFT) calculations of one structure by using the B3LYP hybrid functional and the 6-311 + G (d,p) basis set to provide the relevant frontier orbitals and cyclic voltammetry analysis were also performed.

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