Exploring charge transfer dynamics and photocatalytic behavior of designed donor-acceptor complex: Characterization, spectrophotometric and theoretical studies (DFT/TD-DFT)

A donor-acceptor complex (D-A complex) of excellent photocatalytic activity has been synthesized by stirring the 1:1 equimolar ratio of donor (3,5-dimethylpyrazole) and acceptor (3,5-dinitrobenzoic acid) at room temperature. Intermolecular attraction occurs by the formation of hydrogen bond between nitrogen of donor and hydroxy function of the acceptor forming N+-H center dot center dot center dot O- bond. The prepared sample was established via standard analytical techniques of SEM, UV-vis, FTIR, H-1 NMR, TG-DTA and X-ray structural measurements, and computational analysis has also been carried out. Its photocatalytic activity was thoroughly investigated and maximum degradation efficiency of 99.7% of the methylene blue (MB) has been achieved by irradiation of UV light for 90 min based on adsorption of dye and the active species produced during the whole process of degradation and photocatalysis. Moreover, scavenging has also been performed for the determination of active species during the photocatalytic activity and chemical oxygen demand (COD). Results showthat hydroxyl and superoxide radical play the key active species and hole plays a supplementary role during the process of degradation of MB. Computational analysis performed on the prepared donor-acceptor complex [(DMPy)(+)(DNB)(-)] utilizing density functional theory (DFT). Hypothetical calculations (B3LYP/6-311 (d, p)) level, the band gap was found to be 4.64 eV from the HOMO to the LUMO by the frontier molecular orbital energies (FMO). (C) 2020 Elsevier B.V. All rights reserved.