The Extended Hydrogen Bond: A Coupling Pair of Flexible and Polarizable Dipoles

Being essential to life on earth, the hydrogen bond and its configuration, performance, and functionality become increasingly inspiring. We humbly share a three-body coupling X:R-Y system involving a pair of retractable and polarizable Z-X and R-Y dipoles. The (:) is the negative polar end of a dipole. The X:R-Y bond covers at least four situations, meets the unique criterion of force combination, and possesses at least five characteristics. Specifically, the lone-pair-engaged N/O:H-O/N/C bonds feature properly the performances of H2O and CHNO molecular assemblies; the dipolar MP or atomic vacancy V0 replaced MP:R-Y bonds could coordinate molecular physisorption for catalysis and hydrogen storage; and the polarity-inverted M^+-O_2-:M^P formed during chemisorption drives the oxidation bonding and electronic dynamics. The combination of X:R attraction and X:Y repulsion is decisive to the performance of the X:R-Y system that follows the hydrogen bond cooperability and polarizability (HBCP) regulation in the segmental length, energy, and specific heat [Sun et al, Phys Rep 2023; 998:1-68]. The X:R-Y exhibits extraordinary adaptivity, recoverability, sensitivity, catalytic capability, and chemical reactivity. A perturbation such as mechanical compression, thermal loading, electronic polarization, or molecular undercoordination changes the X—Y distance by lengthening one segment and shortening the other. The HBCP premise has substantiated the understanding of water ice anomalies, molecular hydration interfaces, CHNO energetic assemblies, and oxygen chemisorption, inspiring promising ways of thinking about single-atom catalysis and low-dimensional high-TC superconductivity. Further extension of this amplification to other areas such as biological science and cell engineering would be even more fascinating and promising.