What is a Schiff Base?
A Schiff base is a compound with the general structure R2C=NR‘ and is considered as subclasses of imines, being either secondary aldehydes or secondary ketimines depending on their structure. The term is commonly used as a synonym to azomethine (which refers to secondary aldimines). These compounds are named after the Italian chemist Hugo Schiff. Many systems exist for the nomenclature of these compounds.
Schiff’s bases are aldehyde- or ketone compounds where the carbonyl group is replaced by an azomethine or imine group. These are commonly used for industrial purposes and also exhibit a wide range of biological activities. These are the most widely used organic compounds which are used as intermediates in organic synthesis, catalysts, pigments and dyes, polymer stabilizers, etc.
Synthesis of Schiff Bases
Schiff’s bases are formed when any primary amine reacts with an aldehyde or a ketone under specific conditions. In other words, it is a nitrogen analogue of a ketone or aldehyde where the carbonyl group has been replaced by azomethine or imine group. The first preparation of imines in the 19th century by Schiff. Schiff followed a classical method in the synthesis of Schiff Bases, it involves condensation of a carbonyl compound with the help of amine under the distillation of azeotropic and to remove water formed in the system, molecular sieves are used. Later many ways of Schiff bases synthesis are invented.
Biological Applications
Antimalarial activity
Malaria is a chronic disease which was neglected for many years. Every year, nearly 500 million people are affected by this disease and approximately 1-3 million people die among them. Schiff’s bases are proved to be a very good source for the design of antimalarial agents. Schiff Base 5 was the most effective antimalarial agent among the other synthesized bases.
Antibacterial Activity
Bacteria is the root cause of many infectious diseases and responsible for an increase in the mortality rate. There are different kinds of bacteria, and they exhibit a lot of resistance to antibiotics. Schiff’s bases have emerged as promising antibacterial agents. For example, Mycobacterium can be effectively treated with N- (salicylidene) -2- hydroxyaniline.
Antifungal activity
Schiff bases with a 2,4-dichloro-5-fluorophenyl moiety have been proven to restrict the growth of fungi like Aspergillus flavus, Aspergillus fumigatus, Trichophyton mentagrophytes, and Penicillium marneffei.
Conjugated Schiff Bases
Conjugated Schiff Bases possess some interesting optoelectronic properties and have been used in electronics such as the organic field-effect transistor, Perovskite solar cells, and electrochromic devices. These are also used in the manufacturing of Covalent Organic Framework that is used for gas storage.
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