Abstract Two amphiphilic poly(m,p-phenylene)s were synthesized through Suzuki polycondensation from 1,3-phenylene dibromide bearing solubilizing tri- or tetra(ethylene glycol) chains and 1,4-phenylene diboronic acid diester. Unlike its tri(ethylene glycol
Synthesis and self-association of an imine-containing m-phenylene ethynylene macrocycle
The purpose of this study was to test the suitability of the imine bond as a structural unit within the backbone of phenylene ethynylene macrocycles and oligomers by determining the ability of m-phenylene ethynylene macrocycle 1 to form π-stacked aggregates in both solution and the solid state. Macrocycle 1, with two imine bonds, was synthesized in high yield from diamine 4 and dialdehyde 5. The imine-forming macrocyclization step was carried out under a variety of conditions, with the best yield obtained simply by refluxing the reactants in methanol. The self-association behavior of 1 in various solvents was probed by 1H NMR. The association constants (KE) in acetoned6 and tetrahydrofuran-d8 were determined by fitting the concentration-dependent chemical shifts with indefinite self-association models. The results showed that solvophobically driven intermolecular π-π stacking could be preserved in the imine-containing m-phenylene ethynylene macrocycles. Interestingly, in acetone macrocycle 1 exhibited a stronger tendency to form a dimer rather than higher aggregates. We postulate that this behavior may be due to electrostatic attraction between dipolar imine groups. The solid-state packing of 1 was studied by wide- and small-angle X-ray powder diffraction (WAXD and SAXD). Bragg reflections of 1 were consistent with a hexagonal packing motif similar to our previous studies on m-phenylene ethynylene macrocycles that formed columnar liquid crystal phases.
Zhao, Dahui,Moore, Jeffrey S.
p. 3548 - 3554
(2007/10/03)
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