Correlation between Solid-State and Solution Conformational Ratios in a Series of N-(o-Tolyl)Succinimide Molecular Rotors

Abstract

The syn-anti conformational equilibrium of a library of 30 N-(o-tolyl)succinimide molecular rotors was measured in solution via 1H NMR and in the solid-state via X-ray crystallography. A strong correlation was observed between the solution and solid-state mole fractions of syn-conformers (χsyn). All rotors, even those with a small conformational preference in solution (±0.15 kcal/mol), displayed the same conformation in their crystal structures. The conformational preferences in the crystals tended to be more pronounced with a predominance of all syn- or anti-structures. However, when the rotors had no conformational preference in solution, the conformational preferences in the crystal structures varied widely.