Regarding inorganic chemistry, coordination chemistry is at the forefront of innovation and exploration. Since this subfield of chemistry has garnered so much interest and produced valuable outcomes, it has quickly become a top research priority. Schiff-based coordination compounds have significantly influenced the development of coordination chemistry [1,2]. Transition metals, non-transition metals, and a wide range of ligands have been successfully incorporated into synthetic chemical entities with remarkable stability. Analytical chemistry, chemical industry, medicinal chemistry, agricultural chemistry, and bioinorganic chemistry are some areas where metal complexes are helpful [[3], [4], [5], [6]].

Investigating inorganic substances with biological significance is another rapidly expanding area of study. The metals play crucial roles in a wide variety of biological activities. Many different types of processes in the life sciences rely on metal ions, and their functions and levels of complexity can range widely. Another study area is how synthetic inorganic compounds interact with biological systems and their constituents. Researchers with a strong background in inorganic chemistry are needed in all of these fields because of the importance of their work to medical progress. Collaborations between chemists, biologists and medical researchers are anticipated to make up much of the study.

Copper is the sole essential noble metal because it involves many biological processes [7,8]. Copper complexes have been studied for a wide variety of therapeutic applications, including as antimalarial [9,10], antifungal [11,12], and antimicrobial agents [[13], [14], [15]] for the cure of Alzheimer's disease [16,17] owing to its neurologically protective action; and, more recently, as possible medications for treating Parkinson's disease [18,19], amyotrophic lateral sclerosis (ALS) [20,21], inflammatory disorders (such as rheumatic arthritis) [22,23], wounds on the skin [24,25], cardiovascular conditions [26,27], and leishmaniasis [28,29]. A significant amount of study has been done on them, particularly regarding how they work as anticancer agents; nonetheless, their action method is not yet entirely known, and it deserves more investigation.

Many fascinating aspects of coordination chemistry can be linked directly to the initial studies of inorganic ligands in coordination molecules. Researchers are particularly interested in heterocyclic compounds with donor atoms like sulphur, nitrogen, oxygen, amino nitrogen, azomethine nitrogen, and alcoholic or phenolic oxygen. Schiff bases are versatile ligands widely used in coordination chemistry due to their unique properties such as stability, denticity and easy synthesis [30]. The delocalized orbitals of Schiff bases allow for efficient electron transfer, making them ideal for applications in organic electronic devices [[31], [32], [33]] and photovoltaics [34,35]. Additionally, their malleable behaviour enables the design and synthesis of Schiff-base based materials with tailored properties, further expanding their potential in emerging technologies. The multiple ligating sites of Schiff bases also make them excellent candidates for complexation with metal ions, facilitating the development of novel metal-organic frameworks [[36], [37], [38], [39]] and coordination polymers [[40], [41], [42]]. The growing interest in Schiff bases stems from their remarkable characteristics and potential for advancements in diverse scientific disciplines. Schiff base complexes are particularly interested in studying model compounds and have critical biological applications [[43], [44], [45]]. Transition metal Schiff base compounds have attracted much attention in the chemical community over the past few decades. Since the chemistry of Schiff base complexes is particularly interesting to us, we will briefly cover this topic.

Hugo Schiff (1834–1915), an Italian-German chemist, is credited with synthesizing the first Schiff base in 1864. These compounds have an azomethine or imine group. Schiff reported a conventional synthesis in which an aldehyde or ketone was condensed with a primary amine in an azeotropic distillation [[46], [47], [48]]. In reality, this condensation is reversible. Removing the formed water to bring the reaction balance to the right through a carbinolamine intermediate is necessary to achieve high yields(Scheme 1).

In addition to their many uses as intermediates in chemical synthesis, chemosensors [49,50], polymer stabilisers [51,52], food additives [53], dyes [54] and catalysts [55], Schiff bases also have a wide variety of other applications. Small Schiff base ligands with N-heterocyclic aromatic ring in which the heteroatom can coordinate to the metal ion are expected to induce a reasonable extent of planarity to the complexes because of rigidity introduced in the ligand framework by the coordinating heterocycle. Also, Schiff base metal complexes have the potential to facilitate the generation of ROS, which in turn leads to the initiation of DNA damage and disruptions in mitochondrial function. Ultimately, this cascade of reactions results in the activation of apoptosis. However, the incorporation of co-ligands, such as diimine ligands [56,57], terpyridine [58], quinolone [59], and salicylic acid, has the potential to affect the planarity and hydrophobic nature of metal complexes, as well as their coordination geometry.

Consequently, this can increase the affinity of these complexes for DNA binding and ultimately enhance the chemotherapeutic effectiveness of metal-based agents. In this review, we provide an overview of the most recent developments in the study of multidentate Schiff bases and the corresponding metal complexes, emphasising the properties and applications of these materials for practical applications.