Synthesis and electrochemical properties of homo- and heterodimetallic diethynylethene bisphthalocyaninato complexes

A series of molecular dyads, consisting of two homo- or heterodimetallic (M = M' = Zn-II or M = Zn-II, M' = Con) phthalocyaninato complexes bridged by mono- and bis-DEE [(E)-1,2-diethynylethene, (E)-hex-3-ene-1,5-diyne] fragments, was prepared by Pd(0)-catalyzed cross-coupling reactions or by oxidative Glaser-Hay coupling, respectively. The electronic properties of these extensively linearly pi-conjugated materials were investigated by W-visible spectroscopy and electrochemically [cyclic voltammetry and Osteryoung square wave voltammetry], and the spectroscopic data were compared to those of previously prepared phthalocyanine (Pc) dyads, in which benzene rings of the two Pc chromophores are bridged by ethynediyl and buta-1,3-diynediyl linkers, respectively. Whereas the electronic absorption spectra did not reveal significant bathochromic shifts of the Sorer and Q-bands with increasing extension of the linearly pi-conjugated nanomaterials, substantial electronic communication between the two Pc units in the dyads across the DEE bridges was revealed in the electrochemical studies.