A new aguanidine-based bis Schiff base for highly selective Al³⁺ recognition, BSA binding studies and theoretical...

Herin, the successful synthesis of a bis Schiff base (L) has been achieved using 2-hydroxy-1-naphthaldehyde and 1,3-diaminoguanidine as raw materials, which was further characterized by infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance hydrogen spectrum. Moreover, spectroscopic experiments demonstrated that the probe L showed good selectivity and visual detectability for Al³⁺. Its detection limit (DL) is 2.04 × 10^-8 mol·L^-1, which represents a significant improvement over the detection limits of published fluorescent probes of Schiff base. Furthermore, the analysis of the Job's plot revealed a 1:1 stoichiometric relationship between Al3⁺ and L. The refinement mechanism entails the complexation of Al³⁺ ions with two nitrogen atoms present in the Schiff base imine moiety and two oxygen atoms derived from carboxylate and phenolic groups. Additionally, quantum mechanical calculations involving density functional theory (DFT) and molecular docking analysis demonstrated that the interaction between L and BSA was primarily achieved through hydrogen bonding underlying the binding process. The binding energy of BSA protein with small molecules was found to be -7.758 kcal/mol, indicating a strong binding affinity between BAS and L molecules. The thermodynamic parameters, ΔG, ΔH and ΔS for the binding phenomenon indicated that the main interaction force between L and DNA was hydrogen bonds and van der Waals forces with a spontaneous process. In conclusion, this particular Schiff base demonstrates significant potential for the precise detection of Al³⁺ within an environmental context. The investigations into the interactions between this bis-Schiff base L and BSA (bovine serum albumin) reveals the significant role of hydrophobic cavities in the protein's folded structure.