Mechanochemical Tuning of the Binaphthyl Conformation at the Air-Water Interface.

Gradual and reversible tuning of the torsion angle of an amphiphilic chiral binaphthyl, from -90° to -80°, was achieved by application of a mechanical force to its molecular monolayer at the air-water interface. This 2D interface was an ideal location for mechanochemistry for molecular tuning and its experimental and theoretical analysis, since this lowered dimension enables high orientation of molecules and large variation in the area. A small mechanical energy (<1 kcal mol(-1) ) was applied to the monolayer, causing a large variation (>50 %) in the area of the monolayer and modification of binaphthyl conformation. Single-molecule simulations revealed that mechanical energy was converted proportionally to torsional energy. Molecular dynamics simulations of the monolayer indicated that the global average torsion angle of a monolayer was gradually shifted.