STRUCTURAL EFFECTS ON THE DISPROPORTIONATION EQUILIBRIUM OF TETHERED TETRAPHENYLETHYLENE RADICAL-ANIONS

The electrochemistry of four bis[n.l]metacyclophanylidenes has been studied by cyclic and differential pulse voltammetric methods. The potential differences between the first and second reduction steps for these cyclophanes depend on the length of the hydrocarbon tethers and therefore on the magnitude of phenyl ring torsion. This behavior can be correlated with the photophysical properties of these compounds, on the basis that the lowest singlet excited state is isolobal with the dianion. Since the potential difference between the first and second reduction steps is related to the disproportionation equilibrium constant, phenyl ring torsion, rather than olefinic torsion, may play a major role in determining the ion pairing and electrochemical properties of tetraphenylethylenes. © 1990, American Chemical Society. All rights reserved.