Theoretical study on L-H⁺-L with identical donors: Short strong hydrogen bond or not?

Short strong hydrogen bonds (SSHBs) play a crucial role in many chemical processes. Recently, as the representative of SSHBs, [F-H-F]^- was experimentally observed. [F-H-F]^- has a symmetric structure, which can be described as a H⁺ acid shared by two terminal F^- donors (F^--H⁺-F^-). To explore whether two identical donors are bound to result in SSHBs, we performed theoretical studies on a series of compounds (L-H⁺-L) with two identical electron donors (L corresponds to donors containing group 14, 15, 16, and 17 elements). The results show that identical donors do not definitely lead to SSHBs. Instead, typical hydrogen bonds also exist. Both electronegativity and basicity contribute to the patterns of hydrogen bonds, where more electronegative and weaker donors benefit to SSHBs. In addition, it was found that zero-point energies also respond to the hydrogen bonding systems. This systemic work is expected to provide more insights into SSHBs.