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

Abstract

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 (1(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, (1)H NMR spectra, X-ray crystallography, and microcalorimetric titrations. Significantly, the interpenetration of 1(4-) with N,N'-dimethyl-2,7-diazapyrenium salt (DMDAP(2+)) gives an extraordinarily strong association constant (K(a)) up to 10(8) 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 1(4-) with DMDAP(2+) and methyl viologen (MV(2+)), in which DMDAP(2+) is internally encapsulated in the cavity of 1(4-), whereas MV(2+) is externally embedded in the crystallographic lattice to form the ternary supramolecular assembly of MV(2+)·DMDAP(2+)⊂1(4-). We also envision that the Ka gradient obtained in our systematic work illustrates a new and elegant strategy for attaining multicomponent nanomaterials engineered at a molecualr level.