Synthesis, characterization, and study of the optical properties of new Schiff bases

Abstract

Schiff bases have attracted considerable interest in recent years owing to their uses in optoelectronics and their easy synthesis. This study involved the preparation of Schiff bases via a condensation reaction between Folic acid (FA) and two separate aldehyde derivatives, 3,4-dimethoxy benzaldehyde and 4-pyridinecarboxaldehyde, yielding two unique Schiff base compounds ((E)-(4-(((2-((3,4-dimethoxybenzylidene)amino)-4-oxo-3,4-dihydropteridin-6-yl)methyl)amino)benzoyl)-L-glutamic acid (F1) and (E)-(4-(((4-oxo-2-((pyridin-4-ylmethylene)amino)-3,4-dihydropteridin-6- yl)methyl) amino) benzoyl) -L-glutamic acid (F2), respectively. The synthesized Schiff base compounds have been characterized using FT-IR, UV-Vis,¹H-NMR, ¹³C-NMR, antibacterial, and antioxidant studies, confirming the effective synthesis of the targeted molecular structures. The UV-Vis spectra revealed that the absorption range of compounds largely falls in the ultraviolet region, which is a result of electronic excitation of π→π* and n→π*π in the conjugated system. The optical studies revealed a refractive index of (n=1.2) for both compounds, and a wide optical energy band gap that ranged between (3.86-3.78ev), indicating that such materials are not conductive to electricity and therefore, act as optically transparent insulators. The result also showed significant effectiveness of the two compounds, as compound F1 showed the highest antibacterial activity with an inhibition diameter of (24mm) at a concentration of (1mg/ml) compared to F2. The compounds also recorded antioxidant activity of (86.678%) for F1 and (85.492%) for F2. Moreover, the properties of the synthetic compounds make them exceptionally suitable for optoelectronic and photonic applications such as UV-blocking finishes, anti-reflective coats, optical filters and insulating coats in electrical and optical equipment.