Synthesis, photophysical properties, and density functional theory studies of phenothiazine festooned vinylcyclohexenyl‐malononitrile

Abstract

A novel phenothiazine derivative conjugated with vinylcyclohexenyl-malononitrile (PTZ-CDN) was synthesized through the Knoevenagel reaction of 10-octyl-10H-phenothiazine-3,7-dicarbaldehyde with 2-(3,5,5-trimethylcyclohex-2-en-1-ylidene)malononitrile and fully characterized. The UV-vis absorption spectra of PTZ-CDN in different solvents showed a λ max band at 497-531 nm with a high molar extinction coefficient attributed to intramolecular charge transfer (ICT) with the characteristics of a π-π* transition. Increasing the solvent polarity resulted in a bathochromic shift of λ max. The PTZ-CDN fluorescence emission spectra were more sensitive to increasing the solvent polarity than the absorption spectra; they displayed a blue shift of λ em by 85 nm. To understand the behaviour of the PTZ-CDN derivative, Stokes' shift (Δ νÞ with respect to the solvent polarity, Lippert-Mataga and linear solvation-energy relationship (LSER) models were applied in which the LSER showed better regression than the Lippert-Mataga plots (r 2 = 0.9627). Finally, the TD-density functional theory (DFT) electronic transition spectra in dioxane and dimethyl formamide (DMF) were calculated. The DFT data showed that λ max resulted from the support of the highest occupied molecular orbital to the lowest unoccupied molecular orbital transition with 74% and 99% in dioxane and DMF, respectively.

Synthesis and characterization of phenothiazine sensor for spectrophotometric and fluorescence detection of cyanide

“…PTZS 13 CNMR spectra also revealed significant evidence. The original chemosensor signal at 158.82 ppm vanished, and a new signal at 80 ppm appeared, as shown in Figure 8.…”

“…The Sigma-Aldrich Company provided the reagents and solvents, which were all utilized in line with the instructions. Using a Bruker Avance 850 MHz spectrometer, 13 C and 1 H NMR spectra of the…”

“…Component 2 and malononitrile underwent a Knoevenagel condensation process to produce the chemosensor. The purity of the sensor was confirmed using the spectra from the 1 H NMR, 13 C NMR, and ESI-MS. Compound characterization charts in great detail may be seen in the Supplementary material.…”

“…To further understand the nature of cyanide interactions, the changes in 1 H, 13 CNMR spectra, and IR spectra brought about by adding cyanide ions to the probe were monitored. This action would impair the electron transfer between the donor and the acceptor in molecules, enabling the optical changes to be observed.…”

“…[12] Phenothiazine (PTZ) and its derivatives, which have great biological and pharmacological action, have attracted considerable interest in some disciplines, including biology, medicine, and chemistry. [11,13] They have also been transformed into some products, including optoelectronic substances (such as light-emitting diodes), antioxidants in the manufacturing of fuels and lubricants, and biomedicines (varied biological activities such as antifungal and antibacterial). [14,15] Phenothiazine, an electron-donating group, can also create fluorescent probes that are founded on the ICT instrument pattern by combining with robust acceptors to create a 'pull-push' system.…”