binuclear

Binuclear is a term used in chemistry to describe a compound or coordination complex that contains two metal centers. These centers may belong to the same element (homometallic) or to different elements (heterometallic). The two metals are typically connected by bridging ligands or, less commonly, by a direct metal–metal bond. The binuclear motif is common in inorganic and organometallic chemistry, catalysis, and bioinorganic chemistry.

The structural hallmark of binuclear species is the linkage between the two metals, often through oxo, hydroxo, carboxylato, or alkoxo bridges, though some systems feature a direct M–M bond. The metal–metal distance and the electronic communication between centers influence magnetic coupling, redox properties, and cooperative reactivity, enabling multi-electron processes or activation of substrates that single centers cannot achieve easily.

Binuclear centers occur in nature and in materials. Classic examples are binuclear copper sites in enzymes such as hemocyanin and tyrosinase, which participate in oxygen transport and oxidation chemistry. Dinuclear iron sites are also known in certain oxygenases. In materials and catalysis, binuclear metal clusters appear in molecular catalysts, magnetic materials, and as motifs in metal–organic frameworks, where cooperative effects between the two metals enhance performance.

Synthesis and characterization involve assembling two metal ions with suitable bridging ligands or combining two preformed mononuclear fragments. Characterization relies on X-ray crystallography to determine geometry, along with spectroscopic methods (UV–Vis, EPR) and magnetic measurements to probe electronic communication and reactivity.

Relevance lies in the cooperative activity of two centers, which enables multi-electron redox chemistry, selective oxidation, and models of biological active sites.