Interplay between n→π* Interactions and Dynamic Covalent Bonds: Quantification and Modulation by Solvent Effects

Orbital donor–acceptor interactions
play critical roles
throughout chemistry, and hence, their regulation and functionalization
are of great significance. Herein we demonstrate for the first time
the investigation of n→π* interactions through the strategy
of dynamic covalent chemistry (DCC), and we further showcase its use
in the stabilization of imine. The n→π* interaction between
donor X and acceptor aldehyde/imine within 2-X-2′-formylbiphenyl
derivatives was found to significantly influence the thermodynamics
of imine exchange. The orbital interaction was then quantified through
imine exchange, the equilibrium of which was successfully correlated
with the difference in natural bond orbital stabilization energy of
n→π* interactions of aldehyde and its imine. Moreover,
the examination of solvent effects provided insights into the distinct
feature of the modulation of n→π* interaction with aprotic
and protic solvents. The n→π* interaction involving
imine was enhanced in protic solvents due to hydrogen bonding with
the solvent. This finding further enabled the stabilization of imine
in purely aqueous solution. The strategies and results reported should
find application in many fields, including molecular recognition,
biological labeling, and asymmetric catalysis.