Shape of things to comeResearchers show that hydrogen can form multicenter bonds

Hydrogen is the simplest of the elements, consisting of one proton and one electron. It is typically expected to exhibit simple chemistry when forming molecules or solids. Thus, hydrogen atoms almost always form a single bond to just one other atom, leading to a two-center bond with two electrons. There are exceptions to this rule, but they are rare, with only a few cases when hydrogen bonds simultaneously to two other atoms, forming a three-center bond.

This is why the following is big news: Researchers at the University of California Santa Barbara have shown that, under the right circumstances, hydrogen can form multicenter bonds, in which one hydrogen atom simultaneously bonds to as many as four or six other atoms. Tested for hydrogen in metal oxides, the discovery could have a broad range of technological impact. Professor Chris G. Van de Walle and Project Scientist Anderson Janotti, both of the Materials Department of the College of Engineering at UC Santa Barbara, have shown that multicoordinated hydrogen is a likely explanation for electronic conductivity in metal oxides. Metal oxides are widely used in everything from sunscreen to sensors.

Hydrogen can replace an oxygen atom and form a multicenter bond with adjacent metal atoms. For example, in ZnO, hydrogen equally bonds to the four surrounding Zn atoms, becoming fourfold coordinated. These multicenter bonds are highly stable and explain previously puzzling — an hertofore inexplicable — variations in conductivity as a function of temperature and oxygen pressure. The results suggest that hydrogen can be used as a substitutional dopant in oxides, a concept that is counterintuitive and should be of wide interest to researchers.

-read more in this Phyorg report