There has been a lot of recent interest in the use of metal-ligand binding as the thermodynamic driving force for the self-assembly of ditopic ligands into supramolecular polymers.1 Further to some of our preliminary work that involved the metallosupramolecular polymerization of a small-molecule ditopic ligand,2 we recently reported on the supramolecular polymerization of a new conjugated macromonomer that displayed appreciable mechanical properties.3 The macromonomer was derived by functionalizing a low-molecular weight poly(2,5-dialkoxy-p-phenylene ethynylene) (PPE) core as an example of conjugated polymers with well-known optoelectronic properties4 with 2,6-bis(1'-methyl-benzimidazolyl)pyridine (Mebip) ligands5 in the two terminal positions. Polymers produced by polymerizing this macromonomer though the addition of stoichiometric amounts of Zn2+ or Fe2+ could readily be processed into films and fibers that displayed excellent mechanical properties,but the coordination to Zn2+ and Fe2+ markedly influenced the optical properties of the PPE core. While the interaction with metals often provides interesting opportunities for tailoring the opto/electronic properties of ligand- containing conjugated molecules,6,7 sometimes effects such as charge trapping or fluorescence quenching occur. For example,in the case of the aforementioned PPE-Mebip metallopolymers,the luminescence was strongly (Zn2+) or even completely (Fe2+) quenched. With the objective to minimize electronic interactions between the PPE moieties,and noting that examples of conjugated metallopolymers in which the conjugated moieties and the organometallic motifs are electronically decoupled are limited,we here report the investigation of new supramolecular metallopolymers based on a PPE-Mebip macromonomer in which conjugated core and ligands are separated by non-conjugated hexamethylene spacers (Figure 1).
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