Benzyl Effects of Supramolecular Architectures Constructed by p-Sulfonatocalix[4]arene and Viologen Guests: from Simple 2:1 Complex to Polymeric Capsules

Abstract

Two novel supramolecular assemblies have been constructed by p-sulfonatocalix(4)arene (C4AS) and viologen guests, showing that C4AS presents the supramolecular architecture of spectacular polymeric capsules in the presence of benzyl viologen, whereas it forms a simple host-guest 2:1 complex with methyl viologen. As a significant and interesting topic of crystal engineering, the construction of supramolecular assemblies has attracted more and more attention in recent years. p-Sulfonatocalix(n)arenes (CnAS, n ) 4, 5, 6, 8), with high water-solubility, multicharged rims, and flexible frameworks, are demonstrated to be a well-known kind of versatile building blocks. 1 Up to now, several kinds of spectacular architectures besides the conventional bilayer array 2 have been fabricated by CnAS upon complexation with various types of guest molecules and/or metal ions, such as molecular capsules, 3 the ferris wheel, 4 the Russian doll, 5 the helical array, 6 water-filled channels, 7 coordination and hydrogen-bonding polymers, 8 honey- comb aggregates, 9 spheroidal and tubular arrays, 10 etc. 11 Among the family of these water-soluble calixarenes, p-sulfonatocalix- (4)arene (C4AS), as the smallest conformation-constrained ana- logue, emerges to be the most popular subunit that is convenient for studying the influences of different guests upon the formation of supramolecular assemblies from host-guest complexes. 1a,b Possessing an intrinsic bowl shape, C4AS can form molecular capsules in the presence of diverse guest molecules, such as crown ethers, 1a,b,3a amino acids, 12 nucleic acid bases and derivatives, 13 etc., which have been carefully investigated by Raston and co- workers, revealing that the encapsulated guests show noncovalent interactions like hydrogen bonding, π-stacking, and hydrophobic effects, with the cap molecules, which contribute much to the formation and stabilization of the capsules. Our recent work also reported that C4AS forms a 2:2 bis-molecular capsule with phenanthroline, in which two guests are included into the cavity