Biphenyl has a solution-phase equilibrium dihedral angle of 30-40�. Although biphenyl achieves excellent extended conjugation when planar, the steric hinderance of the ortho hydrogens prevents this geometry from being an energetic minimum. The dihedral angle of biphenyl-containing compounds greatly affects physical properties such as electronic absorption, emission, and conductance. Most biphenyl-containing compounds have a fixed dihedral angle and thus fixed physical properties. However, we have synthesized a reversible lactone �tether� between the two rings that should force a planar geometry. This �smart� biphenyl lactone contains a methoxy donor and a nitro acceptor at the 4 and 4' positions to affect charge transfer through the ring system. By varying the pH, we can reversibly open and close the lactone which should switch the molecule in and out of planarity. The design, synthesis and characterization of this �smart� biphenyl will be presented.

Smart biphenyl lactone containing a nitro acceptor and methoxy donor capable of pH-driven dihedral angle switching

243rd National Meeting (2012)

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