Systematic study of the fluorescent properties of cinnamaldehyde phenylhydrazone and its interactions with metals: Synthesis and photophysical evaluation

Hydrazones are organic compounds with applications in various fields of research, including fluorescent applications. In this investigation, the compound cinnamaldehyde phenylhydrazone was synthesized by condensation between cinnamaldehyde (1) and phenylhydrazine (2). Furthermore, the photophysical properties were evaluated in the presence and absence of inorganic salts, and it was found that the fluorescence intensity selectively decays with CuCl₂ in a thermodynamically spontaneous process (ΔG = negative). In addition, computational approaches were used, which identified the transfer of electrons from highest-occupied molecular orbital HOMO of compound 3 to the lowest unoccupied molecular orbital (LUMO) of CuCl₂ as the key interaction for quenching the fluorescence intensity of cinnamaldehyde phenylhydrazone. Additionally, the potential application of compound 3 as a Cu²⁺ chemosensor in different water samples was evaluated. This compound was found to exhibit better recovery of Cu²⁺ in natural water samples (higher than 99.3%) than in drinking water (66%).