CONFIRMATION OF SYN-ANTI ISOMERISM OF 2,5-DIMETHOXYDICYANOQUINONEDIIMINE RADICAL-ANIONS IN SOLUTION

The conformational behaviour of 2,5-dimethoxydicyanoquinonediimine rad ical anions has been studied in polar solvents with ESR and proton END OR spectroscopy. Both syn and anti isomers of the radical anions have been identified. The two conformers differ in molecular symmetry and h yperfine coupling between the unpaired electron with nearby protons. S eparate spectra of the conformers have been obtained with ENDOR-induce d ESR. Finally, from electronic spin relaxation, the activation energy for the interconversion process between the syn and anti conformers w as estimated at 28.5 kJ/mol (6.8 kcal/mol). (C) 1997 Published by Else vier Science B.V.