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

The syn-anti conformational equilibrium of a library of 30 N-(o-tolyl)succinimide molecular rotors was measured in solution via H-1 NMR and in the solid-state Via Xray crystallography A strong correlation was observed between the solution and solid-state mole fractions of syn-conformers chi(syn)). 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.