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‘ = Co II ) 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 π-conjugated materials were investigated by UV−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 Soret and Q-bands with increasing extension of the linearly π-conjugated nanomaterials, substantial electronic communication between the two Pc units in the dyads across the DEE bridges was revealed in the electrochemical studies.