Synthesis of novel keto-bromothymol blue in different media using oxidation–reduction reactions: combined experimental and DFT-TDDFT computational studies

Abstract

A crystalline ((3-bromo-5-isopropyl-2-methyl-4-oxocyclohxa-2,5-dien-1-yl)methyl 4ʹ-hydroxy-5ʹ-isopropyl-2ʹ-methyl-[1,1ʹbiphenyl]-2-sulfonate) [BTB]Keto was synthesized in different media at 25 °C based on an oxidation method in the presence of potassium permanganate. The redox reactions occur in alkaline and acidic media. In alkaline medium, two distinct stages were observed: The first stage was relatively fast and the second stage was relatively slow. The first step coexists with the formation of intermediate complexes involving transient species relatively quickly of the blue hypomanganate (V) and green manganate (VI). The slowly decomposed intermediate formed to produce soluble colloidal manganese (IV) and the BTB keto-derivatives as second slow-stage oxidation products. But in acidic medium, oxidation reaction occurs in one stage because the first stage was found to be very fast and cannot be followed and the second stage was found to be slow so the reaction occurs in one stage (slow stage) to give rise to the final oxidation product [BTB]Keto. Thin films were produced through physical vapor deposition. Both the resulting dye particles and prepared thin films were deeply discussed using various techniques including Fourier transform infrared (FTIR), X-ray diffraction (XRD), ultraviolet–visible spectroscopy (UV–Vis), and optical properties. DMol3 and Cambridge Serial Total Energy Package (CASTEP) program performed the optimization of the samples using density functional theory (DFT). An XRD and FT-IR study established the structural properties of the resultant dye. The XRD tests of thin films (monoclinic 2) display crystal structure. An optical measurement found that with growing photon energy the optical constants (refractive index n, absorption index k, dielectric constants, and optical conductivity) decreased. The optical properties of the dye thin films found in model FTIR, XRD, and CATSTEP are in strong alignment with the experimental research. The dye thin films show a compelling outcome to be a successful choice for applications in optoelectronics and solar cells. Experimental XRD data of both [BTB]TF and [BTB]keto thin films