Dynamic Formation of Noncovalent Calixsalen Aggregates

Abstract

A procedure for studying "dynamic structural behavior" of large chiral macrocycles is presented. Ion mobility MS, diffusion-ordered NMR spectroscopy (DOSY NMR), and optical rotation (OR) measurements, supported by calculations, are used together as effective complementary methods to study dynamic formation of noncovalent aggregates. It is shown that the monomer-dimer equilibrium is driven by π-π or CH-π interactions and controlled largely by the substitution pattern of the calixsalen skeleton.

Specific Noncovalent Association of Chiral Large‐Ring Hexaimines: Ion Mobility Mass Spectrometry and PM7 Study

“…[21] Data processing was carried out with Drift-Scope 2.7 mobility environment software, and the experimental collision cross sections were calculated by using the available spreadsheet. IM cell calibration was carried out by using protonated monomers and dimers of calixsalen with known collision cross sections.…”

“…[40] To make this procedure as accurate as possible the reference compounds should fulfill requirementss uch as appropriate charges tate and molecular similarity to the measured species. Therefore, due to the very limited conformational flexibility of calixsalens, [21] they should be good standards forI Mm easurements, and hence the [M+ +H] + and [2 M+ +H] + ions of calixsalens were used as reference ions. In general, flexible molecules with aw ide range of stable conformationst hat depends trongly on the experimental conditions are not good candidates as standards for IM-MS measurements.…”

Awkwardly‐Shaped Dimers, Capsules and Tetramers: Molecular and Supramolecular Motifs in C5‐Arylated Chiral Calixsalens

“…Macrocycles substituted at the C‐5 position by small and/or polar groups such as halogens form mostly tail‐to‐tail dimers (Figure b) by mutual insertion of one aromatic moiety of each monomer into the cavity of a partner. The formation of the tail‐to‐tail dimers is highly stereoselective and is driven solely by noncovalent interactions, such as dipole–dipole and π–π stacking , . Calixsalens having bulky groups of spherical symmetry at the C‐5 position crystallize as capsules (head‐to‐head dimers) capable of solvent molecule entrapment (Figure c).…”

“…Calixsalens having bulky groups of spherical symmetry at the C‐5 position crystallize as capsules (head‐to‐head dimers) capable of solvent molecule entrapment (Figure c). The capsules are only stable in the solid state and decompose immediately after dissolution …”

Ca2+‐Assisted DOSY NMR: An Unexpected Tool for Anomeric Identification for d‐Glucopyranose

“…In our research group DOSY NMR has been used to obtain otherwise inaccessible information, e. g. structural information of labile glycosylation intermediates studied using low temperature 1 H‐ and 19 F‐DOSY NMR, the complex formation between a Lewis acid catalyst and a reactant . With the aid of a matrix, such as surfactants or polymers, an improved separation of signals in the diffusion dimension has expanded the DOSY technique into an interesting and sophisticated analytical tool to obtain to study aggregation status in solution, detect the host‐guest complex formation and capture of reactive intermediates in situ ,. A draw‐back of using matrix assisted DOSY is the additional NMR signals from the matrix, which potentially can overlap with the peaks of interest and hence complicate the analysis.…”