Multistep Synthesis and Photophysical Investigation of Novel Pyrazoline, a Heterocyclic D-π-a Chromophore (PTPB) as a Fluorescent Chemosensor for the Detection of Fe³⁺ Metal Ion

A pyridine-pyrazoline (2-(3-(pyridin-2-yl)-5-(3,4,5-trimethoxyphenyl)-4,5-dihydro-1H-pyrazol-1-yl)benzo[d]thiazole) (PTPB) has been designed and synthesized by the reaction of chalcone with 2-hydrazinylbenzo[d]thiazole. PTPB was further conformed by the FT-IR, 1H-NMR and 13 F. Ran, Y. Liu, D. Zhang, M. Liu, and G. Zhao, “Discovery of Novel Pyrazole Derivatives as Potential Anticancer Agents in MCL,” Bioorganic and Medicinal Chemistry Letters 29, no. 9 (2019): 1060–4.[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]N-NMR spectroscopic techniques. The solvatochromic behavior of PTPB with electron donating and accepting group was investigated in nonpolar, polar aprotic and protic solvents experimentally. The photophysical behavior of the PTPB in different solvent was attributed to the intramolecular charge transfer (ICT) of the compound along with specific and nonspecific interaction with different solvents. On view of the effect of different type of interaction on the photophysical parameters such as stokes shift, dipole moment oscillator strength and fluorescence quantum yields have been calculated with respect to polarity of the solvent. In addition, pyridine-pyrazoline (PTPB) can use as fluorescent chemosensor to determine the Fe3+ metal ion with high selectivity among the series of cations in aqueous dimethylformamide (DMF). The recognition mechanism of PTPB toward Fe3+ has been investigated in detail by Benesi–Hildebrand, Stern–Volmer and job’s plot measurements and PTBP forms 1:1 complex with Fe3+ metal ion and displays fluorescent quenching behavior.