Date of Award
Program or Major
Doctor of Philosophy
Howard R Mayne
The reaction of fullerene with pentacene and various 6,13-disubstituted pentacenes has been studied and the formation of cis-bisfullerene adducts has been achieved. The reaction of fullerene with pentacene was studied with the goal of preparing cis-1 and trans-2 bisfullerene adducts. Instead, the solution phase Diels-Alder reaction between fullerene and pentacene yields a C 2v symmetric monoadduct, 3, in 59% yield.*.
Semi-empirical PM3 calculations suggest that fullerene should react favorably with 6,13-disubstituted pentacenes such that molecules similar to 1 and 2 would form. Several 6,13-disubstituted pentacenes were synthesized and subsequently reacted with fullerene resulting in the formation of various cis-bisfullerene adducts in high yield. The reactions are completely regioselective, cycloadditions occurring exclusively across the 5,14- and 7,12-positions of the pentacene backbone, and highly cis-stereoselective as well. The corresponding trans-bisfullerene adducts are not detected above trace levels. The reactions proceed through the formation of CS symmetric monoadducts, some of which form in high yield and are easily isolated. 6,13-Diethynyl substituted pentacenes are especially prone to CS monoadduct formation in good yield. NMR spectroscopy in conjunction with mass spectrometry and X-ray structure analysis has enabled a thorough characterization of the products.*.
A combination of experimental data, model compound studies, and computational results suggest that favorable pi-stacking interactions between fullerene moieties in the ground state and in transition states are responsible for the high cis-stereoselectivities observed in these reactions whether they be run under kinetically controlled or thermodynamically controlled conditions. Electrochemistry of two bisfullerene adducts has been studied. Separate I electron reductions for each fullerene moiety on one of the bisfullerene adducts, are resolved at low negative potential. Bisfullerene adducts are also susceptible to chemical reductions and reactions with Zn dust in 2 different solvents have been studied.
Mack, James II., "Diels -Alder reactions between fullerene and various pentacenes" (2000). Doctoral Dissertations. 2147.