Journal of the American Chemical Society, Vol.142, No.13, 6085-6092, 2020
Binding Energy as Driving Force for Controllable Reconstruction of Hydrogen Bonds with Molecular Scissors
Hydrogen bonds are one of the most important directional intermolecular interactions and play key roles in chemical and biochemical systems, but there is still a lack of prediction and understanding of their control. Herein, hydrogen-binding energy (E-HB) acted as a driving force for controllably reconstructing hydrogen bonds with molecular scissors. We related hydrogen-binding energies of the donor-acceptor couple (E-HB,E-2) and the donor itself (E-HB,E-1) and Delta G based on Delta G = a(1)E(HB,1) + a(2)E(HB,2) + a(3). When E-HB,E-1 and E-HB,E-2 satisfy the condition Delta G < 0, the acceptor is predicted as molecular scissors with sufficient reconstruction capacity in breaking the initial hydrogen bonds and forming new ones. Remarkably, we developed an experimental method to determine the E-HB values by a linear equation as a function of chemical shifts (delta) (ln delta + sigma(delta) = -E-HB/RT + A), which is innovational since in the former research E-HB can only be deduced from empirical formulas and DFT calculation. On that basis, the hydrogen bonds of alpha-cellulose were broken and re-formed in molecular scissors-consisting deep eutectic solvents, leading to the white powder transforming into a hydrogel and colorless and transparent thin film materials with distinct crystalline structure, surface flatness, and morphology.