Binding Behaviors of p-Sulfonatocalix[4]arene with Gemini Guests

Abstract

A dozen of homoditopic cations, possessing different spacer lengths and rigidities, as well as sizes, shapes, and charges of terminal groups, were synthesized as candidate gemini guests for the complexation of p-sulfonatocalix[4]arenes (SC4A). The 12 gemini guests are divided into five species according to the different terminal groups: imidazolium (G1-G3), pyridinium (G4-G6), quinolinium (G7), viologen (G8-G11), and 1,4-diazabicyclo[2.2.2]octane (DBO, G12). Their binding structures and stoichiometries with SC4A were examined by NMR spectroscopy, which is helpful to construct diverse highly ordered assemblies. The obtained results show that the length of the linkers, as well as the charge numbers on the end groups have a pronounced effect on the binding stoichiometry, whereas the size and shape of the terminal groups have no significant influence. Furthermore, both the stability constants and thermodynamic parameters of SC4A with the terminal subunits were determined by the isothermal titration calorimetry experiments, which are valuable to understand the binding behavior, giving quantitatively deep insight.

Photolysis of an Amphiphilic Assembly by Calixarene-Induced Aggregation

“…SC4A was synthesized and purified according to procedures reported previously. 31 The storage solution of SC4A (1 mM) was adjusted to pH 7.2 using aqueous NaOH (1 M), and the pH value for the SC4A−AnPy assembly was 6.3, which is consistent with that of free AnPy. Such a slightly acidic environment could facilitate the decomposition of 9-anthryl ether.…”

The “True” Affinities of Metal Cations to p‐Sulfonatocalix[4]arene: A Thermodynamic Study at Neutral pH Reveals a Pitfall Due to Salt Effects in Microcalorimetry

“…For example, Guo, Liu, and co‐workers long conducted ITC measurements with SC4 in 0.1 M buffer concentration,15, 46, 47 but recently abandoned this routine practice and now use neutralization with base rather than (or in addition to) 0.1 M phosphate buffer to minimize competitive binding by addition of alkali metal ions 47. 60 The importance of avoiding buffers in titration experiments with SC4 was also recently emphasized by Biczók and co‐workers58 and Hof and co‐workers 61…”

Amino Acid‐Functionalized Calix[4]Resorcinarene Solubilization by Mono‐ and Dicationic Surfactants

“…Studying process of solubilization of hydrophobic substrates is one of the standard techniques for determination of the surfactant critical micelle concentration (CMC) [30,31]. In the present work, we focused on the study of the surfactant concentration above the CMC to analyze effect of added calix [4]resorcinarenes on structural transitions in the micellar structure [32][33][34]. Solubilization capacity of micellar systems was evaluated by determining the maximal solubility of the calixarene substrates in surfactant solutions.…”