Biphenyl and Terphenyl Lactone pH-Driven Molecular Switches

Abstract

The physical properties of biaryl-containing compounds are known to be highly dependent on molecular geometry. Two 6H-benzo[c]chromen-6-one derivatives were synthesized, where a lactone "tether" between the two phenyl rings should force a planar geometry. These biphenyl lactones contain a methoxy electron donor and a nitro or cyano electron acceptor at the 4 and 4' positions to affect charge transfer through the ring system. By varying the pH, the "tether" could be reversibly and rapidly opened and closed and thus switch the molecule in and out of planarity. The purpose of this study was to analyze the pH-driven dihedral angle switching by UV-Vis and fluorescence spectroscopy.