2,5-DisubstitutedN, N′-Dicyanoquinone Diimines (DCNQIs) − Syntheses and Redox Properties

Quinones 1a−q and DCNQIs 2a−g have been synthesized in order to investigate substituent effects. It was necessary to employ novel synthetic routes for the introduction of iodine into 1f (7), the trifluoromethyl group into 1g−i, deuterium into 1m−p, and especially for the chloride/fluoride exchange of 1j to 1k, and 1l. With few exceptions both 1 and 2 undergo reversible electron transfer in two steps including thermodynamically very stable radical cations (lg KSEM > 10, cyclic voltammetry). Linear correlations have been found between E2 (OX/SEM) data of 1 and 2 with (σm + σp)/2 and between E2 of 1 and 2. Correlations have also been found between E2 and the LUMO energies of 1 and 2. The crystal structure of quinone 1i shows some special interactions due to the two CF3 groups, whereas the structures of DCNQIs 2d and 2g link up with those evaluated earlier.