Controllable Synthesis and Biological Application of Schiff Bases from d-Glucosamine and Terephthalaldehyde

Abstract

Theoretically, the two aldehydes of terephthalaldehyde (TPA) are equivalent, so the single or double Schiff base from TPA and d -glucosamine (Glc) may be formed at the same time. However, it is preferred to produce separately a single Schiff base ( L 1 ) or double Schiff base ( L 2 ) for different synthesis systems of anhydrous methanol or water–methanol. We calculated the Δ r G of the formation of compounds L 1 and L 2 by density functional theory (DFT). In an anhydrous methanol system, the Δ r G values of L 1 and L 2 are both below zero and L 2 is lower, suggesting the spontaneous formation of the two Schiff bases. Though adjusting the molar ratio of Glc to TPA, L 1 and L 2 both were separately formed in anhydrous methanol. However, in the water–methanol system, L 2 was absent, which is most likely due to higher Δ r G (4.95 eV) and better water solubility. The results also exhibits that the positive charge of C in −CHO for TPA is smaller in a mixed solvent than that in methanol, which confirms that the nucleophilic reaction of the Schiff base is more difficult in a mixed solvent. Therefore, we could realize to control the synthesis of a pure single or double Schiff base from Glc and TPA by adjusting the molar ratio and solvent. The as-prepared two kinds of Schiff bases have strong optical properties, high bacteriostatic activity, and can be used as fluorescent probes for tumor cell imaging.

Mitochondria-Targeted Luminescent Organotin(IV) Complexes: Synthesis, Photophysical Characterization, and Live Cell Imaging

“…Similarly, Schiff bases as fluorescent probes have attracted a great deal of attention as the specific substituents on the ligand moieties change their photophysical properties remarkably. , Schiff bases are a great source of luminescent cell probes because they are low in cytotoxicity, easy to synthesize, noninvasive, and highly photostable. Some specific biomarkers such as coumarin-, diaminomaleonitrile-, salicylaldehyde-, carbazole-, and glucosamine-, Schiff base derivatives have been described previously. Until now, fluorescent Schiff bases , and main-group metals coordinated with Schiff bases − have been used in cell imaging; however, tracking specific organelles such as mitochondria is scarce.…”

Physicochemical and Theoretical Characterization of a New Small Non-Metal Schiff Base with a Differential Antimicrobial Effect against Gram-Positive Bacteria

“…Schiff bases are compounds harboring a functional group called azomethine (–C=N–), a linker between structures showing the formula R 1 R 2 –C=N–R 3 , where R1, R2, or R3 could be substituted aryl or alkyl groups, among others [ 8 , 9 , 10 ]. Schiff bases exhibit a broad range of applications, including anticancer drug candidates [ 11 ], where their use in antimicrobial chemotherapy is progressively gaining attention [ 8 , 12 ].…”

The Effect of Temperature and Thermodynamic Parameters on the Ionization Constants of Some Imines Derived from Vanillin with substituted aniline

“…Schiff [1] bases are compounds containing the imine group or what is known azomethine group (-CH=N-). Schiff [3,2] was the first to prepare these compounds in 1864, by condensing primary amines with aldehydes or ketones [5,4]. Schiff bases have the general formula of R1R2-C=N-R3.…”