Abstract
A number of hydroxyl-substituted azacalix[4]pyridines were synthesized using Pd-catalyzed macrocyclic “2+2” and “3+1” coupling methods and the protection–deprotection strategy of hydroxyl group. While the conformation of the these hydroxyl-substituted azacalix[4]pyridines is fluxional in solution, in the solid state, they adopted shape-persistent 1,3-alternate conformations. Besides, X-ray analysis revealed that the existence of hydroxy groups on the para-position of pyridine facilitated the formation of solvent-bridged intermolecular hydrogen bonding for mono-hydroxyl-substituted while partial tautomerization for four-hydroxyl-substituted macrocycles, respectively. Taking the hydroxyl-substituted azacalix[4]pyridines as molecular platforms, multi-macrocycle-containing architectures and functional building blocks were constructed. The self-assembly behavior of the resulting building blocks was investigated in crystalline state.
Highlights
Design of ingenious macrocyclic molecules has been one of the driving forces to promote the major advances of supramolecular chemistry, which has been manifested by examples of crownether, cyclodextrin, calixarene, resorcinarene, cucurbituril, calixpyrrole, pillarenes, etc. (Lehn et al, 1996)
The reactions in the presence of trimethylammonium in CH2Cl2 resulted in two pyridine-contained functional building blocks 21 and 22 in 64 and 52% yields, respectively (Scheme 5)
The unique structure and tautomerization of the macrocycle in solid state were revealed by X-ray analysis
Summary
Design of ingenious macrocyclic molecules has been one of the driving forces to promote the major advances of supramolecular chemistry, which has been manifested by examples of crownether, cyclodextrin, calixarene, resorcinarene, cucurbituril, calixpyrrole, pillarenes, etc. (Lehn et al, 1996). Macrocyclic compounds provide unique models in the study of non-covalent interactions, and they have been serving as building blocks in the construction of high-level supramolecular architectures. Typical examples such as by anchoring derivative groups on the macrocycles, versatile building blocks, have been prepared and widely applied to the fabrication of molecular devices and smart materials (Chen and Liu, 2010; Guo and Liu, 2014; Ma and Tian, 2014; Strutt et al, 2014; Caricato et al, 2015; Le Poul et al, 2015; Parisi et al, 2016; Murray et al, 2017; Pazos et al, 2018; Wang, 2018; Ogoshi et al, 2019). We report the facile synthesis and structure of a number of hydroxy-substituted azacalix[4]pyridines These functionalized macrocycles as molecular platform to construct high-level architectures and functional building blocks were demonstrated
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