PROBING DELOCALIZATION ACROSS ALKYNE-CONTAINING LINKAGES - SYNTHESIS AND CYCLIC VOLTAMMETRY OF BRIDGED PHENYLENEDIAMINES

This paper presents the synthesis of N,N,N',N'-tetraethyl-1,4-phenylen ediamines bridged by ethynylphenyl-ethynyl and diethynyl linkages. The se compounds are of interest to determine if the N,N,N',N'-tetraethyl- 1,4-phenylenediamines exhibit delocalized mixed oxidation states when oxidized electrochemically. -Butoxy-2,5-bis(N,N-diethylamino)-4-ethyny lbenzene was a key intermediate, and nucleophilic addition of lithium (trimethylsilyl)acetylide to 2,5-bis(N,N-diethylamino)-1,4-benzoquinon e provided an efficient synthesis of this compound. This intermediate was then assembled into the redox assemblies of interest in high yield by use of palladium-catalyzed cross-coupling and copper-catalyzed oxi dative home-coupling protocols. Cyclic voltammetry of these compounds indicate that the N,N,N',N'-tetraethyl-1,4-phenylenediamine redox unit s behave independently and that the interactions are principally elect rostatic. As a result, we conclude that the electrochemically generate d radical cations and dications are highly localized.