Thermodynamics and Structures of Complexation between Tetrasulfonated 1,5-Dinaphtho-38-crown-10 and Diquaternary Salts in Aqueous Solution

The readily available recognition motifs with high affinity and selectivity can undoubtedly expedite the development of host–guest chemistry from fundamental research to practical application in miscellaneous fields. In this work, a series of guest-mediated [2]­pseudorotaxanes are successfully constructed by the incorporation of tetrasulfonated 1,5-dinaphtho-38-crown-10 (<b>1</b>^4–) with three kinds of dicationic substrates, i.e., the diquaternary salts of 4,4′-bipyridine, 1,10-phenanthroline, and 2,7-diazapyrene, which are comprehensively explored by means of UV/vis, ¹H NMR spectra, X-ray crystallography, and microcalorimetric titrations. Significantly, the interpenetration of <b>1</b>^4– with <i>N</i>,<i>N</i>′-dimethyl-2,7-diazapyrenium salt (DMDAP²⁺) gives an extraordinarily strong association constant (<i>K</i>_a) up to 10⁸ M^–1 order of magnitude in water. Moreover, the spectroscopic and crystallographic analyses jointly demonstrate that there is a competitive binding process in the complexation of <b>1</b>^4– with DMDAP²⁺ and methyl viologen (MV²⁺), in which DMDAP²⁺ is internally encapsulated in the cavity of <b>1</b>^4–, whereas MV²⁺ is externally embedded in the crystallographic lattice to form the ternary supramolecular assembly of MV²⁺·DMDAP²⁺⊂<b>1</b>^4–. We also envision that the <i>K</i>_a gradient obtained in our systematic work illustrates a new and elegant strategy for attaining multicomponent nanomaterials engineered at a molecualr level