A Schiff base colorimetric probe for real-time naked-eye detection of biologically important fluoride and cyanide ions: Single crystal, experimental, theoretical, biological and antioxidant studies

Abstract

The synthesis and characterization of a Schiff base (E)-2-((3,5-bis(trifluoromethyl)phenylimino)methyl)-4-methylphenol from the reaction of 2-hydroxy-5-methylbenzaldehyde with 3,5-bis(trifluoromethyl)aniline has been studied using X-ray single-crystal techniques and compared to the results from theoretical calculations using density functional theory (DFT). We have investigated the antimicrobial activities of the title compound for their minimum inhibitory concentration (MIC). We have also examined the interactions with DNA by using the UV–Visible and agarose gel electrophoresis methods. It is shown that the title compound interacts with CT-DNA via electrostatic binding. The antioxidant activity of the title compound was measured by using the DPPH method. It is furthermore shown that it indicates lower antioxidant activity than butylated hydroxytoluene (BHT). It is also found that activity remained constant with increasing compound concentration. We have also investigated the colorimetric response of the title compound in dimethyl sulfoxide (DMSO) to the addition of an equivalent amount of anions (F−, Br−, I−, CN−, SCN−, ClO4−, HSO4−, AcO−, H2PO4− and OH−). In this context, while the addition of F− and CN− anions into the solution containing the title compound resulted in a significant colour change, the addition of Br−, I−, SCN−, ClO4−, HSO4−, AcO−, H2PO4− and OH− anions resulted in no colour change. In the presence of these anion solutions, only F− and CN− solutions underwent impressive colour change detectable with the naked eye from colourless to orange-red and purple, and orange and blue-violet in both daylight and UV light, respectively. The most discernible colour change in the Schiff base was caused by F− and CN−, which demonstrated that the Schiff base could be used to selectively detect F− and CN−. Also, various sensor applications of Schiff base were investigated. For this, the alumina oxide sheet and filter paper impregnated with the title compound were used.