Stereochemistry and thermodynamics of the inclusion of aliphatic and aromatic anionic guests in a tetracationic calix[4]arene in acidic and neutral aqueous solutions

Different and Often Opposing Forces Drive the Encapsulation and Multiple Exterior Binding of Charged Guests to a M4L6 Supramolecular Vessel in Water

“…Data given in Table 2and Figure 3clearly show that the logK valuesf or the exterior ion-association equilibria increasew ith the size of the ammonium guests;h owever,t hese processes are driven by differenta nd often opposing enthalpic and entropic contributions, [44] and thus splitting the Gibbs energy term into the DH8 and DS8 components reveals significant and individualf eatures and differences that are not visible in the DG8 term. [43,[45][46][47] Exterior binding of the smaller Me 4 N + ,E t 4 N + , and 5-Spiro + guests (whicha re less hydrophobic) is mainly attributed to enthalpically favorable electrostatic and cation-p interactions between the highlya nionic and aromatic exterior of the host and the positively charged ammonium guests. Such attractive forces have been previously observed in solidstate [20] and diffusion NMR studies.…”

Calorimetric Investigation of Nano-Basket’s Binding

“…The comparison of log K for the first binding is more significant. (7,8) in cone conformation showed clear one-step binding. Derivatives (9-13) depicted two-step binding towards with log K differences of 1 to 3 between the first and second binding constants.…”

“…Influence of the conformation variation: Conformational variation had an important influence on cation binding affinity for conformers (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). As shown in Table-1, the log K values for sodium binding decreased from the 1,2-alternate conformation to the partial-cone conformers.…”

“…Isothermal titration calorimetry (ITC) as an analytical tool directly determines the binding heat of two species 1 and are used to characterize the binding thermodynamics in the chemical and the biological systems such as complexation of isoleucine by phosphorylated calix [4]arene 2 , solvation changes in cyclodextrin complexes 3 , complexation of glyco-and tauroconjugated bile salts with modified β-cyclodextrins 4 , association of surfactants with β-cyclodextrin 5 and proteins 6 . The other hosts:guests interactions of cations and anions 7 using isothermal titration calorimetry has been reported in the literatures. Not only isothermal titration calorimetry determines the binding stoichiometry and affinity as well as the binding entropy and enthalpy, but also it used to characterize the self-association of some polymers 8 and the binding constant of water-soluble calix [4,6]arene sulfonates towards acetylcholine 9 .…”

Anion binding to a tetracopper resorcinarene-based complex

“…These include the calix [4]arene that has cationic ammonium groups for binding (13) and a calix [4]arene with amidourea groups that is a colorimetric anion receptor (14). Along with these are calix [4]pyrroles with etheric handles which show a strong affinity for chloride (15,16), a zinc cyclen calix [4]arene that binds anions (17) and a resorcinarene compound that binds anions through C -H interactions (18).…”