Light and Solvent Effect on Isomerization and Excimer Formation of Pyrene—Schiff Base Conjugate Sensing Aromatic Analytes

Abstract Pyrene is a fluorescent polycyclic aromatic compound and it will be fascinating whether its excimer complex can be used for sensing of aromatic analytes. So, ( E )‐3,4,5‐tris(dodecyloxy)‐N'‐(pyren‐1‐ylmethylene) benzohydrazide (P@M) is synthesized. The E (trans)‐isomer of P@M exhibits bright fluorescence for excimer formation in non‐aromatic solvents for closeness of pyrene moieties of E ‐P@M. Upon photo‐irradiation with λ = 254 nm E ‐P@M changes to Z ‐P@M (cis ‐isomer) at 10 −4 M concentration in methyl cyclohexane (MCH) yielding diminished PL‐intensity. Interestingly, upon photo irradiation with λ = 365 nm, the Z‐isomer of P@M reverts to E ‐isomer indicating that, E‐Z isomerization of P@M is reversible in nature. The UV–vis absorption band at 370 nm of E‐P@M in MCH at 10 −4 M shifts to 344 nm for its Z‐isomer formation. The thick supramolecular aggregated morphology of E‐ P@M changes to flowery needle like morphology after photo irradiation with λ = 254 nm. The fluorescent emission of E ‐P@M in MCH is quickly quenched on addition of different aromatic analytes through both static and dynamic path way. In solid state E ‐P@M also sense aromatic vapors efficiently via fluorescence quenching.