Topological Analysis of the Electron Density of Molecules with Bridging Hydrogens To Tackle the Chemical Structure Monolith

The assumption, common at the undergraduate level, that hydrogen with its single electron can form only one covalent bond is belied by the many structures that have been characterized with hydrogens bonded to two atoms. The 3-center bond responsible for such bridging hydrogens is facilitated by the spherical distribution inherent to the 1s electron. Here we demonstrate how topological analysis of the electron density of molecules with bridging hydrogens can inform a deeper appreciation of the character and complexity of the chemical bond. DFT calculations are performed to generate the electron density for the experimental structures of a range of complexes with bridging hydrogens. Analysis using both the Atoms in Molecules (AIM) perspective and a range of electron indicators and localization functions demonstrates the utility of topological analysis for the detection and characterization of multi-center bonding.