Coordination and Bioinspired Inorganic Chemistry Research

Details of Research Areas

Our research integrates coordination chemistry, bio-inspired inorganic chemistry, crystallography, and molecular magnetism to develop functional transition metal and lanthanide complexes with applications in catalysis, small-molecule activation, and biomimetic systems. Current research directions include:

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Coordination Chemistry of Transition Metals and Lanthanides

• Design, synthesis, and structural characterization of novel coordination complexes of first-row transition metals and lanthanide ions, with emphasis on understanding their structure–property relationships.

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Single-Crystal X-ray Crystallography

• Determination of molecular and crystal structures using single-crystal X-ray diffraction to establish precise structural features and correlate them with chemical reactivity and physical properties.

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Redox-Active Ligand Systems

• Our research focuses on the design and synthesis of transition metal complexes supported by amine- and phenol-based ligands (N4, N3O, N2O2 donor), which provide versatile coordination environments for stabilizing different oxidation states and reactive intermediates. We are particularly interested in redox-active (non-innocent) ligand systems, including catecholate and aminophenolate frameworks, that actively participate in electron-transfer processes. These ligands can generate stable ligand-centered radical species, such as semiquinone (SQ), iminosemiquinone (ISQ), and phenoxyl radicals, upon coordination to metal ions. By combining electrochemical, spectroscopic, magnetic, and single-crystal X-ray crystallographic studies, we investigate their electronic structures, metal–ligand redox cooperativity, and chemical reactivity. These studies provide valuable insights into biological redox processes and aid in the rational design of functional catalysts, magnetic materials, and bio-inspired coordination complexes.

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Small-Molecule Activation and Bio-Inspired Catalysis

Our research is directed toward the development of bio-inspired coordination complexes that emulate the structure and function of metalloenzymes involved in small-molecule activation and biological redox transformations. By combining synthetic inorganic chemistry with electrochemistry, spectroscopy, and structural characterization, we aim to understand the fundamental mechanisms governing catalytic processes and to develop efficient molecular catalysts.

• A major focus of our research is the design of functional models of cytochrome c oxidase (CcO). Inspired by the heterobimetallic active site of the enzyme, we develop transition-metal complexes based primarily on copper and iron that can activate molecular oxygen via electrocatalytic oxygen reduction reaction (ORR). Particular emphasis is placed on elucidating the role of the secondary coordination sphere, proton-coupled electron transfer (PCET), ligand architecture, and metal–metal cooperativity in controlling oxygen activation, reactive oxygen intermediates, and selective reduction of O₂ to water. These studies provide fundamental insights into biological respiration while contributing to the development of efficient molecular electrocatalysts for sustainable energy conversion.

• We also develop biomimetic models of catechol oxidase and tyrosinase using first-row transition metal complexes. These studies focus on the activation of molecular oxygen for the oxidation and hydroxylation of phenolic substrates, providing mechanistic insights into enzymatic catalysis by identifying reactive intermediates, including ligand-radical and high-valent metal species.​​​

• Generation, detection, and spectroscopic characterization of high-valent metal–oxo species relevant to biological oxidation processes and oxidation catalysis.

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Multinuclear Metal Complexes and Molecular Magnetism

• Design and synthesis of mononuclear [e.g., TBP Co(II)] to multinuclear metal complexes exhibiting interesting magnetic behavior, with emphasis on magnetic exchange interactions, single-molecule magnetism, and structure–magnetism correlations.