Neutral glycoconjugated amide-based calix[4]arenes: complexation of alkali metal cations in water

Abstract

Cation complexation in water presents a unique challenge in calixarene chemistry, mostly due to the fact that a vast majority of calixarene-based cation receptors is not soluble in water or their solubility has been achieved by introducing functionalities capable of (de)protonation. Such an approach inevitably involves the presence of counterions which compete with target cations for the calixarene binding site, and also rather often requires the use of ion-containing buffer solutions in order to control the pH. Herein we devised a new strategy towards the solution of this problem, based on introducing carbohydrate units at the lower or upper rim of calix[4]arenes which comprise efficient cation binding sites. In this context, we prepared neutral, water-soluble receptors with secondary or tertiary amide coordinating groups, and studied their complexation with alkali metal cations in aqueous and methanol (for the comparison purpose) solutions. Complexation thermodynamics was quantitatively characterized by UV spectrometry and isothermal titration calorimetry, revealing that one of the prepared tertiary amide derivatives is capable of remarkably efficient (log K ≈ 5) and selective binding of sodium cations among alkali metal cations in water. Given the ease of the synthetic procedure used, and thus the variety of accessible analogues, this study can serve as a platform for the development of reagents for diverse purposes in aqueous media.

Design of a Thiosemicarbazide-Functionalized Calix[4]arene Ligand and Related Transition Metal Complexes: Synthesis, Characterization, and Biological Studies

“…As the third generation of supramolecular hosts, calix[ n ]arenes have attracted considerable attention in a wide range of either demonstrated or potential applications on the basis of their molecular recognition capabilities (Gutsche, 2008; Neri et al, 2016). These applications most notably include direct chemical sensing systems for both ions and neutral molecules (Sliwa and Girek, 2010; Brunetti et al, 2016; Sun et al, 2016; Yeon et al, 2016; Teixeira et al, 2017; Augusto et al, 2018; Cindro et al, 2018; Sarkar et al, 2018), but the host–guest chemistry of calix[ n ]arenes has also been investigated for use in chemical extraction (Du et al, 2018), catalysis (Homden and Redshaw, 2008; Shirakawa and Shimizu, 2018), and various biological/biomedical uses (Perret and Coleman, 2011; Nimse and Kim, 2013; Durso et al, 2016).…”

The Role of Triazole and Glucose Moieties in Alkali Metal Cation Complexation by Lower-Rim Tertiary-Amide Calix[4]arene Derivatives

“…The calixarenes are a class of macrocyclic compounds that can serve as a proof of point [1][2][3][4][5][6]. Their stiff frame and the possibility of both upper-and lower-rim functionalization have led to preparation of exceptional ligands for charged and neutral species in a range of media but very rarely in water [7][8][9][10][11][12][13][14][15][16]. With the aim of overcoming this obstacle, we have recently introduced a new class of water-soluble glycocalixarenes designed for efficient hosting of first-group cations [16].…”

“…Their stiff frame and the possibility of both upper-and lower-rim functionalization have led to preparation of exceptional ligands for charged and neutral species in a range of media but very rarely in water [7][8][9][10][11][12][13][14][15][16]. With the aim of overcoming this obstacle, we have recently introduced a new class of water-soluble glycocalixarenes designed for efficient hosting of first-group cations [16]. These were lower-rim derivatives possessing tertiary amide groups and triazole-sugar subunits (Scheme 1, compound l).…”

“…A simple click-coupling via triazole subunits provides a path for synthesis of calixarene-based receptors for a variety of chemical species in water [23][24][25][26][27]. This is important in the design of selective ligands for metal cations [16], calixarene-based biomimetic compounds [12,28,29], and supramolecular systems, which could be potentially used as biologically active species [30,31]. On the other hand, the role of triazole subunits in alkali metal cation recognition by corresponding lower-rim tertiary amide glycocalixarenes was not previously investigated.…”

Synthesis of Fluorescent Diphenylantracene-Based Calix[4]arene Derivatives and their Complexation with Alkali Metal Cations

“…Apart from that, the complexation process is strongly influenced by the solvation of both reactants and complexes formed. [4,[17][18][19][20][21][22][23][24][25] In this context, the inclusion of solvent molecules in the macrocycle hydrophobic cavity can play an important role in the cation hosting. [20][21][22]24,26,27] The extent of complexation reactions in non-aqueous solvents can also be significantly affected by the process of ion pairing.…”