A Review on the Synthesis, Structural Characterization, and Applications of Transition Metal Complexes

Abstract

Transition metal complexes occupy a central position in modern chemistry owing to their structural versatility, variable oxidation states, tunable electronic properties, and broad spectrum of applications spanning catalysis, medicine, materials science, and environmental remediation. This review consolidates recent advances in the synthesis, structural characterization, and application of coordination compounds derived from d-block metals. Synthetic methodologies are discussed with emphasis on conventional reflux and solvothermal techniques, template-directed assembly, green and microwave-assisted routes, and electrochemical approaches that enable precise control over ligand geometry and metal coordination. Structural characterization is examined through the complementary lens of single-crystal X-ray diffraction, vibrational and electronic spectroscopy, nuclear magnetic resonance, mass spectrometry, and magnetic and thermal analysis, which together establish coordination geometry, denticity, and bonding interactions. The application landscape is surveyed across homogeneous and heterogeneous catalysis, bioinorganic and medicinal chemistry (notably anticancer and antimicrobial agents), luminescent and magnetic materials, and sensing platforms. The review highlights how rational ligand design and metal selection govern the physicochemical behavior of complexes, and how interdisciplinary characterization underpins structure–property correlations. Persistent challenges—including reproducibility, scalability, toxicity, and stability under operational conditions—are identified, and emerging directions such as machine-learning-guided design, sustainable synthesis, and multifunctional complexes are outlined. The synthesis of literature presented here aims to serve as a coherent reference for researchers navigating the rapidly evolving field of coordination chemistry.