DNA-Enforced Conformational Restriction of an Atropisomer

We report the conformational restriction of a freely rotating biaryl derivative resulting in strong exciton coupled circular dichroism between the two nondegenerate fragments of the dyad NP only in the presence of DNA. The napthalenimide-perylenimide dyad NP, an extended 1,1'-binaphthalene derivative, has a rotational barrier of 100 kJ/mol, leading to fast racemization. While end-stacking with a DNA hairpin, NP exhibits a significantly high rotational barrier, an additional 91 kJ/mol, resulting in atroposelective preference. Such reversible conformational constraints using biotemplates show huge potential toward conformational analysis, dynamic kinetic resolution, and asymmetric synthesis. The present work focuses on conformational analysis of a freely rotating biaryl derivative using a combination of techniques such as temperature-dependent UV-vis, circular dichroism, steady-state and time-resolved fluorescence spectroscopy, and molecular dynamics simulation.