Synthesis and Morphology of a Shape‐Persistent Macrocycle with endo‐Amines and an Inner Tetraethylene Glycol Ether Bridge

Abstract

As hape-persistent macrocycle consisting of 2,6disubstituted aniline linked by acetylene, butadiyne, and an inner tetraethyleneglycol bridge was prepared by Pd/Cu homocoupling oxidation reaction. The morphology of the resulting macrocycle was demonstrated and discussed,i ndicat-ing the establishment of channels with amine functional groups inside the pores. Polarized optical microscopy (POM) observation of the macrocyclei ndicated the formation of liquid crystals (LCs) in the heating and cooling processes.The design and synthesis of organic porous nanoobjects have been of great interest during the recent decades due to their potentiala pplications in areaso fg as storage, separation, catalysis, drug delivery,a nd potential two-dimensional (2D) and three-dimensional (3D) structures. [1] Among variousf rameworks investigated, shape-persistent macrocycles (SPMs) consisting of phenyl and ethynylene or butadiyne are of great interest and have received special attentionb ecause of their rigid structure and versatile chemistry. [2] Based on convenient and efficient synthesis methods together with the rich noncovalent interactions including p-p,V an der Waals forces, hydrogen-bondingi nteraction, and so on, nanostructures with definite structuresh ave been obtained and exhibit typical regular morphologies. When the availables ingle crystal structures are viewed, the common features are uniform porosities or tubular channels. [3] Upon the decoration of functional groups inside SPMs, inner functional surfaces can be designed, if they can form the ordered structures. In this respect, Hçger et al. have introduced phenol functional groups to the rotational backbones of SPMs, resultingi nasolvent-responsives olidc hannel morphology. [4] Schlüter and co-workers,b yi ncorporatingb ipyridine backbones into SPMs, revealed that these macrocycles adopt ad if-ferent layered structure due to slight variation of the side chain. [5] In contrast, a tert-butyl-substituted cyclew ith six methoxy functionalg roups has been demonstrated by Oda et al. to have al ayered structure with tubular channels and little pstackedi nteraction, probably due to the bulky side chains. [6] Recent work by Abe et al. illustrated that ordered, p-stacked channels can be obtained with enhanced dipole-dipole interaction of opposing pyridine units on top of each other. [7] Despite the progress described above,h ow to tune the arrangemento ft he building blocks into the desired structures and use the unique properties is still ac hallenge because of the sensitivity of the formed structure to subtle modifications in the backbones, endo-functional groups,o rs ide chains at the exo positions. Recently,w ef ocused on endo-functionalized compound 1,abridged, V-shaped framework with four amine groups (Scheme1), which forms ap orous, 2D-ordered structure on ah ighly oriented pyrolytic graphite (HOPG)s urface. This molecule has the potential to respond to the presence of potassiumc arbonate and can be viewed as am olecular spring. [8] Because it bears amine groups and at ...