A unique trapping by crystal forces of a hydronium cation displaying a transition state structure

An hydronium cation has been discovered which is unique among all crystallographic such ions of the Cambridge Database. Of composition H7O3+ it has a structure that is totally different from those classically known with structures H2O-H2O-H3O+ and H2O-(H3O+)-H2O. Unlike the crystallographically classical ones, the cation discussed here has a bifurcated hydrogen bond. From a central H3O+ moiety a single hydrogen bond donor extends to two adjacent water molecules. Quantum chemical calculations in absence of the crystal environment demonstrate that the bifurcated hydrogen bond structure is that of a transition state for the H7O3+ complex. Thus remarkably, it appears that crystal forces have captured the ion in what would otherwise be a short-lived and unstable transition state formation.