Synthesis, photophysical properties and DFT studies of 2-(3-cyano-4-((2-(4,6-dimethyl-5-nitro-1H-pyrazolo[3,4-b]pyridin-3-yl)hydrazono)methyl)-5,5-dimethylfuran-2(5H)-ylidene)malononitrile dye

The chromophore 2-(3-cyano-4-((2-(4,6-dimethyl-5-nitro-1H-pyrazolo[3,4-b]pyridin-3-yl) hydrazono)methyl)-5,5-dimethylfuran-2(5H)-ylidene)malononitrile (PPHTCF) was synthesized through coupling of diazotized 3-amino-4,6-dimethyl-5-nitropyrazolo[3,4-b]pyridine with 3-cyan o-2-(dicyanomethylene)-4,5,5-trimethylfuran (TCF). The absorption solvatochromism behaviour of PPHTCF, in various solvents, presented delta E-max = +5.40 where the positive sign suggested red shift occurrence, implying that the PPHTCF has more polar lowest excited state than its ground one. While, the PPHTCF fluorescence spectra afforded lambda(em), in 575-633 nm range, and was more dependent on the solvent polarity than the absorption lambda(max), despite both exhibited red shift by 58 and 42 nm, respectively. To discover the PPHTCF solvatochromism behaviour in term of Stokes' shift , both of Lippert-Mataga and linear solvation-energy relationship (LSER) formulations have been utilized and the outcomes endorsed that the later was better than the former (R-2 = 0.9728). Finally, TD-DFT simulated absorption and emission spectra in EtOH revealed that lambda(max) has been resulted mainly from HOMO -> LUMO; HOMO-5 -> LUMO and HOMO-2 -> LUMO transitions, respectively.(c) 2022 The Author(s). Published by Elsevier B.V. on behalf of King Saud University. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In this study, the chromophore 2-(3-cyano-4-((2-(4,6-dimethyl-5-nitro-1H-pyrazolo[3,4-b]pyridin-3-yl)hydrazono)methyl)-5,5-dimethylfuran-2(5H)-ylidene)malononitrile (PPHTCF) was synthesized and its absorption and fluorescence spectra in different solvents were investigated. The results showed solvent solvatochromism behavior and red shift occurrence of PPHTCF. Two mathematical formulas were used to explain the solvatochromism behavior of PPHTCF, and the linear solvation-energy relationship (LSER) formula had a better fit.