Synthesis, characterization of 4,4′-((1E,1′E)-hydrazine-1,2-diylidenebis(methanylylidene)) diphenol and the inclusion complex with γ-cyclodextrin as a fluorescent probe for detection of Al3+

Abstract

The 4, 4′- ((1E, 1′E)-hydrazine-1,2-diylidenebis(methanylylidene)) diphenol (4-HBA) is successfully synthesized utilizing 4-hydroxybenzaldehyde (4-HB) and hydrazine hydrate as the starting materials. The synthesized 4-HBA is confirmed by the spectral analysis of 1H NMR, FT-IR, UV–Visible, and HR-Mass spectroscopy. The inclusion complexes of 4-HBA with γ-cyclodextrin are therefore investigated using UV and fluorescence spectroscopy. When γ-CD combined with 4-HBA, a 1:1 inclusion complex (ICs) is created that causes absorption and fluorescence spectral changes. The molecular computational analysis is carried out utilizing PM3 Gaussian software revealing the orientation of the synthetic 4-HBA within the γ-CD cavity. The HOMO-LUMO band gap and the DFT analysis specifically support the ICs, with the help of energy values and the H-bond distance. The hydrophobic contact between the host and guest molecules is strongly supported by the 1H NMR and 2-D NMR data, with the matching Ar-H proton moving to higher chemical shift values and the strong cross-correlation spot validating the conclusion. Al3+ sensing activity is observed using fluorescent probes in conjunction with UV and FL spectral analysis. Other metal ions are present in the solutions even though they are not readily available, most notably the Al3+ that binds to the fluorescent probe. Here, the Al3+ selective responses, the colour changes at the wavelength regions, and a fluorescence microscopic image of the solution media are also shown. The selected metal ions recovery percentage is used to determine the concentrations in a variety of clean water samples, including tap water, pond water, and also sea water.