ZnH

ZnH is the neutral diatomic molecule formed by one zinc atom bonded to one hydrogen atom. It is considered a transient radical and is not stable under standard conditions; it has been the subject of experimental and theoretical investigations in inorganic chemistry and physical chemistry. The molecule is primarily studied in gas phase or in cryogenic matrices where it can be stabilized long enough for spectroscopy. Its bond is described as a polar covalent Zn–H bond with considerable ionic character due to zinc's electropositivity and the small size of hydrogen. The ground electronic state is predicted to be a doublet, with a sigma-type bond along the internuclear axis; higher electronic states have also been calculated. Cross sections and spectroscopic constants have been reported by various ab initio methods, including multireference and coupled cluster approaches.

Synthesis and detection: ZnH can be generated in the laboratory via laser ablation of zinc in the presence of hydrogen diluted in inert gas, or by photolysis of zinc-containing precursors in a cold matrix. It is typically detected by laser-induced fluorescence, absorption spectroscopy, or mass spectrometry of transient species.

Relevance: ZnH serves as a benchmark system for computational methods in metal–hydrogen bonding and helps in understanding zinc chemistry in flames and plasmas. It also informs studies of metal hydride reactivity and can contribute to models of gas-phase zinc speciation.

See also: zinc hydrides, metal hydrides, diatomic molecules.