Microwave-Assisted Synthesis of Phenyl Quinazoline: Investigation 'ON-OFF-ON' and Latent Fingerprint Applications

Stimuli-responsive materials with donor-acceptor (D-A) systems have significant potential for sensing toxic analytes in solution and solid state. In this regard, a new probe, N, N-dimethyl-4-(4-phenylquinazolin-2-yl) aniline (DAQ), was synthesized using microwave irradiation and characterized using various spectroscopic techniques. The crystal structure analysis revealed that DAQ crystallized in a monoclinic system with a P21/m space group. The probe exhibits fluorescence properties in solid state and solution, with positive solvatochromism observed as solvent polarity increased from hexane to DMF, indicating the existence of D-A structural units. The probe DAQ, exhibited reversible switching behaviour in the solution and solid state, indicating its sensitivity to volatile trifluoroacetic acid (TFA) and triethylamine (TEA) as confirmed by spectrophotometric and spectrofluorimetric studies. The binding constant of probe DAQ with TFA and TEA were studied by the Benesi Hildebrand (BH) plot using UV-Vis spectral titration. The estimated association constant was found to be 1.43 × 10⁴ M^- 1. The DAQ aggregation-enhanced emission properties have been successfully utilized to develop security ink and latent fingerprint information encryption on various substrates in their aggregated solid state. The study reveals that the sensitivity of DAQ warrants application on all forms of forensic evidence.