Hydroxybridged

Hydroxybridged is a descriptor used in inorganic and coordination chemistry to characterize chemical species in which hydroxy groups (OH) act as bridging ligands that connect two or more metal centers or other atoms. The term is most often applied to μ-OH bridges, where a single hydroxide ligand links two metal centers (dinuclear or polynuclear clusters).

In dinuclear and polynuclear metal complexes, hydroxy bridges facilitate magnetic coupling, electron transfer, and catalytic cooperation between centers. Hydroxy bridges can be μ2-OH or μ3-OH bridging two or three metals. The bridging hydroxide can be deprotonated to a hydroxo ligand or protonated to a water bound form, depending on pH.

Formation and stability: hydroxybridged motifs often arise by hydrolysis or condensation of metal-oxo or metal-oxo-hydroxo precursors, and their prevalence is influenced by pH, solvent, and counterions. Bonding geometry varies with metal identity and oxidation state, and M–O–M angles can affect electronic communication between centers.

Relevance: Hydroxybridged motifs occur in synthesis of coordination polymers and metal-organic frameworks, in biomimetic oxidation catalysts, and in models of natural systems such as multicopper or diiron centers involved in oxygen activation. They can modulate acidity, redox properties, and catalytic activity.

See also: hydroxo ligand, μ-OH bridge, μ-oxo bridge, bridging ligand.