A Comprehensive Review on Metal Complexes Structure, Properties, and Applications

Metal complexes, also known as coordination compounds, are chemical species consisting of a central metal atom or ion surrounded by molecules or ions called ligands. These ligands donate electron pairs to the metal center, forming coordinate covalent bonds. The study of metal complexes is fundamental to inorganic chemistry due to their diverse structures, bonding modes, and wide range of applications. Metal complexes play a vital role in catalysis, medicine, and biological systems—examples include cisplatin as an anticancer drug, hemoglobin in oxygen transport, and chlorophyll in photosynthesis. Their stability and properties are influenced by the nature of the metal ion, the type of ligands, and the geometry of coordination. Current research focuses on the design and synthesis of novel metal complexes with improved catalytic efficiency, biocompatibility, and environmental sustainability. These properties can be exploited to enable measurement of analytes that lack the essential chromophoric, fluorophoric, or oxidizable/reducible groups. These properties of metal complexes have spurred the development of analytical methods based on these complexes  for the determination of various analytes, including drugs, metals, nucleic acids, as large and small molecules, across different analytical application.