Development, Structural Evaluation, and Functional Exploration of Metal Complexes with Thiocarbohydrazones as Ligands

Abstract Thiocarbohydrazones (TCHs) are versatile ligands in coordination chemistry, known for their ability to form stable complexes with various metal ions due to their multiple donor sites, including nitrogen and sulfur atoms. The synthesis of TCHs typically involves the condensation of thiocarbohydrazide with aldehydes or ketones, resulting in symmetric or asymmetric derivatives. These ligands exhibit thioketo-thioenol tautomerism, influencing their coordination behavior and the geometry of the resulting metal complexes. Characterization of TCHs and their metal complexes employs techniques such as infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and X-ray crystallography to elucidate structural details. Recent studies have focused on copper (II) complexes with indole-based thiocarbohydrazones, revealing their potential in DNA cleavage applications. These complexes demonstrate significant nuclease activity, suggesting their utility in developing therapeutic agents targeting genetic material. Additionally, TCHs have been investigated for their antimicrobial and anticancer properties. Their metal complexes exhibit enhanced biological activity compared to free ligands, attributed to the increased lipophilicity and stability conferred by metal coordination. For instance, certain copper (II) complexes of thiocarbohydrazones have shown promising antibacterial and antifungal activities, indicating their potential as metallodrugs. The coordination chemistry of TCHs is further enriched by their ability to form mono-, di-, and polynuclear complexes, with structural diversity influenced by factors such as the nature of the metal ion and the substituents on the ligand framework. This versatility allows for fine-tuning the electronic and steric properties of the complexes, making them suitable for various applications, including catalysis and material science. Theoretical studies, including density functional theory (DFT) calculations, have provided insights into the electronic structures and stability of TCH metal complexes. These studies aid in understanding the correlation between the ligand's structural features and the properties of the complexes, guiding the design of new compounds with desired functionalities. In summary, the field of thiocarbohydrazone metal complexes encompasses the synthesis of diverse ligands, detailed structural characterization, and exploration of their potential applications in medicine and materials science. Ongoing research continues to uncover the vast potential of these compounds, with recent studies highlighting their biological activities and theoretical analyses providing deeper insights into their chemical behavior.