Programmed Dynamic Covalent Assembly of Unsymmetrical Macrocycles
摘要:
Unsymmetrical shape-persistent macrocycles have been prepared from diphenylacetylene monomers using imine formation and metathesis. A sequence-directed approach, in which each monomer is uniquely labeled by its N-donor/C-donor sequence, has been used to control the self-assembly and makes possible an added level of complexity in the final structures. To illustrate the potential of this strategy, a series of macrocycles with different side-chain substitution patterns have been prepared, including monofunctionalized and Janus-type structures. We believe this to be the first example of sequence control of dynamic covalent self-assembly and that it will enable the fully covalent synthesis of more complex nanostructures.
[n]-Rung molecular ladders (n = 3-6) have been prepared by reacting discrete, complimentary m-phenylene ethynylene oligomers using imine formation/exchange. The nanostructures, which in the largest case measure approximately 1.6 x 6.2 nm, have been characterized by MALDI mass spectrometry and gel permeation chromatography. Although the ladder structure is a significant component in each case, the formation of higher molecular weight byproducts becomes more pronounced as the length increases. These structures represent an important first step toward the synthesis of larger, more sophisticated two-dimensional molecular grids.