Selective Carboxylate Recognition Using Urea-Functionalized Unclosed Cryptands: Mild Synthesis and Complexation Studies

Abstract

Herein we present the synthesis and evaluation of anion-binding properties of 12 new receptors from the unclosed cryptand family. Their core is built on the stable 26-membered tetraamidic macrocyclic scaffold, whereas various alkyl and aryl urea substituents were introduced after a yield-limiting macrocyclization step (65–98%). The receptors strongly bind anions, in particular carboxylates, even in a highly competitive solvent mixture (DMSO- d 6 + H 2 O 95:5 v/v).

One-Pot Parallel Synthesis of Unclosed Cryptands—Searching for Selective Anion Receptors via Static Combinatorial Chemistry Techniques

“…The use of combinatorial chemistry methods has allowed significant progress to be made in the synthesis of demanding supramolecular systems. In our previous works, 14 we presented efficient synthesis of unclosed cryptands (UCs) by postfunctionalization of the lariat arm after yield-limiting macrocyclization. Therefore, in this work, we decided to apply our well-established knowledge in the design and synthesis of supramolecular ion receptors while harnessing the advantages of static combinatorial chemistry.…”

Anion Recognition by a Pincer-Type Host Constructed from Two Polyamide Macrocyclic Frameworks Jointed by a Photo-Addressable Azobenzene Switch

“…The lariat arm, apart from bringing extra hydrogen bond functionality, introduces a steric hindrance to the binding cavity and further pre-organizes the macrocyclic framework [41][42][43][44]. To date, this robust macrocyclic platform has been utilized for the construction of potent and selective anion receptors [41,[45][46][47][48][49], phase transfer catalysts (PTC) [50,51], and closely packed molecular hosts for solid-state stabilization of transient supramolecular assemblies such as water clusters [52][53][54] and S• • • S chalcogen bonds [55]. Recently, we have developed practical and productive methods for the synthesis of these systems, using templated-macrocyclization protocols [48,55,56] and post-macrocyclization incorporation of lariat arms under mild conditions [43,46,47,56,57].…”

“…To date, this robust macrocyclic platform has been utilized for the construction of potent and selective anion receptors [41,[45][46][47][48][49], phase transfer catalysts (PTC) [50,51], and closely packed molecular hosts for solid-state stabilization of transient supramolecular assemblies such as water clusters [52][53][54] and S• • • S chalcogen bonds [55]. Recently, we have developed practical and productive methods for the synthesis of these systems, using templated-macrocyclization protocols [48,55,56] and post-macrocyclization incorporation of lariat arms under mild conditions [43,46,47,56,57]. The latter strategy was utilized in the construction of a sterically crowded pincer-type system [57] acting as anion receptor for mono-and dicarboxylates.…”

Stabilization of Near Identical Hydrogen Bonded Octameric Water Clusters in Crystal Structures of Three Distinct Non-Charged Polyamide Macrocyclic Host Molecules

“…Unclosed cryptands (UCs) [22][23][24][25][26][27] belong to the class of fairly new macrocyclic receptors, structurally related to well-established cryptands [28][29][30][31][32]. They are, however, much more flexible than their rigid analogs, as they are built from the macroring of various sizes to which is connected a labile intrannular substituent-lariat arm.…”