Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

Abstract

Polarimetry was used to investigate the binding abilities of a chiral calix[4]resorcinarene derivative, bearing L-proline subunits, towards a set of suitably selected organic guests. The simultaneous formation of 1:1 and 2:1 host–guest inclusion complexes was observed in several cases, depending on both the charge status of the host and the structure of the guest. Thus, the use of the polarimetric method was thoroughly revisited, in order to keep into account the occurrence of multiple equilibria. Our data indicate that the stability of the host–guest complexes is affected by an interplay between Coulomb interactions, π–π interactions, desolvation effects and entropy-unfavorable conformational dynamic restraints. Polarimetry is confirmed as a very useful and versatile tool for the investigation of supramolecular interactions with chiral hosts, even in complex systems involving multiple equilibria.

Polyaminoazide mixtures for the synthesis of pH-responsive calixarene nanosponges

“…These molecules were chosen as representative of different structural classes of possible guests, and show significant variations in their molecular properties such as volume, steric hindrance, hydrophobic character or charge status as a function of pH. Indeed, the same guests were already used to test the binding properties of CaNSs examined in our previous work [22], because they have been considered good models of organic pollutants [26–30]; moreover, they have been largely used as probes to investigate the microscopic interactions involved in the binding equilibria with other classes of supramolecular hosts such as calixresorcinarenes and cyclodextrins [31–38]. The results obtained (percent of guest absorbed under the operational conditions chosen, see Experimental) are summarized in Table 1.…”

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

“…A first set of experiments was devoted to p -nitroaniline derivatives 1 – 5 . These substrates, indeed, have been considered a class of probe guests of choice for investigating the formation of host–guest inclusion complexes with cyclodextrins [38–41] and calixresorcinarenes [42], because of both their easy accessibility and the fact that their molecular properties can be largely varied though maintaining a fixed chromophore moiety. The results obtained, expressed in terms of percent of guest absorbed, are summarized in Table 1.…”

“…Thus, everything considered, the affinity of the guest for Ca NSs is confirmed to depend on a fine balance between different factors, namely Coulomb and π···π interactions, and steric effects. The importance of a compromise between these factors for the complexation into calixresorcinarenes has been recently assessed [42]. Moreover, in analogy with the bahavior observed for Cy NSs and CyCa NSs, such a balance seems significantly affected by the reduced dynamic flexibility of the host monomer unit, which is less prone to optimize its conformation upon the structure of the guest, owing to the hyper-reticulated nature of the material.…”

Aminomethylated Calix[4]resorcinarenes as Modifying Agents for Glycidyl Methacrylate (GMA) Rigid Copolymers Surface

“…As a result of these efforts, studies have recently been initiated with the calix[4]resorcinarenes macrocycles as modifiers of polymeric surfaces, mainly because they possess a variety of functional groups that allow selective functionalization, increasing the degree of interaction with the analytes [9]. The versatility of the functionalization of calix[4]resorcinarenes has led to potential applications in other fields, such as chiral nuclear magnetic resonance solvating agents [10,11], chemical receptors for molecules and ions [12,13,14], molecular encapsulation [15,16,17], selective complexation of metal ions and neutral substances [18,19,20], catalysis [21,22], and liquid crystals [23], among others.…”