In [[chemistry]], a '''dihydrogen bond''' is a kind of [[hydrogen bond]], an interaction between a [[metal hydride]] bond and an OH or NH group or another [[proton]] donor. The first example of this phenomenon is credited to Brown and Heseltine.<ref>Brown, M. P.; Heseltine, R. W. "Co-ordinated BH3 as a proton acceptor group in hydrogen bonding" Chemical Communications 1968, page 1551-2. DOI: 10.1039/C19680001551</ref> They observed intense absorption bands in the [[IR spectroscopy|IR band]]s at 3300 and 3210 cm<sup>-1</sup> for a solution of (CH<sub>3</sub>)<sub>2</sub>NHBH<sub>3</sub>. The higher energy band is assigned to a normal N-H vibration whereas the lower energy band is assigned to the same bond, which is interacting with the B-H. Upon dilution of the solution, the 3300 cm<sup>-1</sup> band increased in intensity and the 3210 cm<sup>-1</sup> band decreased, indicative of intermolecular association.
* [[Hydrogen bond]]