[Co(NH)] is a component of some structural biology methods (especially for DNA or RNA, where positive ions stabilize tertiary structure of the phosphate backbone), to help solve their structures by X-ray crystallography or by nuclear magnetic resonance. In the biological system, the counterions would more probably be Mg, but the heavy atoms of cobalt (or sometimes iridium, as in ) provide anomalous scattering to solve the phase problem and produce an electron-density map of the structure.
[Co(NH)] is used to investigate DNA. The cation induces the transition of DNA structure from the classical B-form to the Z-form.