Calixarenes as Hosts for Ammonium Cations: A Quantum Chemical Study and Mass‐Spectrometric Investigations

Rozhenko, Alexander; Schoeller, Wolfgang W.; Letzel, Matthias C.; Decker, Björn; Agena, Ceno; Mattay, Jochen

doi:10.1002/chem.200501520

Cited by 23 publications

(19 citation statements)

References 50 publications

(42 reference statements)

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“…In addition, from the inverse slope of the loading-rate dependency, the molecular lengths can be extracted, yielding χ β = 0.22 nm for ammonium and χ β = 0.38 nm for the trimethyl ammonium ions. These results correspond with the calculated van der Waals diameters of 0.3 nm for ammonium and 0.6 nm for trimethyl ammonium [18]. Summarizing this section, we could show for an artificial host-guest couple that the specific interaction and dissociation are measurable at a single-molecule level for forces in the 100 pN range.…”

Section: Single-molecule Processes Studied By Afm: State Of the Art-tsupporting

confidence: 82%

On the way to supramolecular photochemistry at the single-molecule level

Schäfer

Decker

Letzel

et al. 2006

Pure and Applied Chemistry

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Two examples of artificial supramolecular host-guest systems derived from resorc[4]arenes (calix[n]arenes based on resorcinol) and ammonium ions as guests have been studied by atomic force microscopy (AFM). For the first time, real single-molecule events have been determined for this type of supramolecular complexes and off-rates as well as molecular parameters of single-molecule aggregates such as the depths of the binding pocket (molecular length parameter) could be measured by applying the methods of dynamic force spectroscopy. In addition, this technique was also applied to differentiate between the two states (open and closed) of a photoswitchable resorc[4]arene-anthracene tweezer. An investigation of the exchange rates of various complexes in the gas phase by means of Fourier transform ion cyclotron resonance (FTICR) mass spectrometry confirmed the results of the AFM study.

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Section: Single-molecule Processes Studied By Afm: State Of the Art-tsupporting

confidence: 82%

On the way to supramolecular photochemistry at the single-molecule level

Schäfer

Decker

Letzel

et al. 2006

Pure and Applied Chemistry

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“…These values are qualitatively comparable with calculated van der Waals diameters of 0.3 nm for ammonium and 0.6 nm for trimethyl ammonium. [9] Therefore we can conclude that the steric complementarity of the host and guest plays an important role in the interaction, with cation-p interactions contributing considerably to the molecular binding mechanism. This finding is also consistent for the interaction of the trimethyl ammonium residue with the cavitand because a the positive-charge distribution has been shown to reside on the hydrogen atoms of the methyl groups.…”

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confidence: 90%

“…The binding of cations to the resorc [4]arene cavitand is facilitated by iondipole interactions, although hydrogen bonds and cationp interactions between the positive charge of the ion and the cavitand with the aromatic rings also have considerable influence. [9] The specificity of the binding is governed by the steric complementarity of the host and guest: only cations small enough to fit into the tailored cavity are recognized by the resorc [4]arene cavitand receptor. In our experiments the 2,8,14,20-tetra-(10-(decylthio)decyl) cavitand, which has a calculated cavity width of 0.7 nm, serves as a host and its specific recognition of ammonium ions and ammonium-ion derivatives is tested (Figure 1).…”

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confidence: 99%

“…In our experiments the 2,8,14,20-tetra-(10-(decylthio)decyl) cavitand, which has a calculated cavity width of 0.7 nm, serves as a host and its specific recognition of ammonium ions and ammonium-ion derivatives is tested (Figure 1). [9] To investigate these interactions we applied single-molecule force spectroscopy, a method which uses the deflection of an AFM cantilever to measure minute forces in the picoNewton (pN) range under physiological conditions. In combination with its sub-nanometer spatial resolution, single-molecule force spectroscopy provides, in contrast to standard ensemble experiments, a potent tool to address and manipulate single molecules and investigate forces within and between individual molecules, to yield information about the molecular energy landscape.…”

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Supramolecular Chemistry at the Single‐Molecule Level

et al. 2004

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In supramolecular chemistry [1] synthetically designed organic constituents interact noncovalently, in a directed and specific way to form host-guest complexes of higher complexity. The ability to tailor the molecular interplay with respect of chemical design, specificity, and molecular switching opens up the development of new molecular materials for artificial molecular recognition, molecular organization, and selfassembly. We have used mechanical single-molecule force spectroscopy to investigate the binding of individual resorc-[4]arene-ligand host-guest complexes. By using diluted samples of the host and guest molecules that are modified with a long linker which is attached to an atomic force microscope (AFM) tip, we were able to prevent multiple binding and to observe single host-guest unbinding events in a supramolecular system for the first time. The molecular binding forces, their dependence on external loading rates, the rate of dissociation, and the molecular cavity length directly relate to the molecular properties of the supramolecular species and are consistent with an activated decay of a metastable bound state, a finding already established for biological receptor-ligand complexes. This result allows new insights into the mechanisms, kinetics, and thermodynamics of intermolecular association in chemistry and biology, and opens new possibilities in the investigation, design, and development of synthetic receptor systems.Calixarenes are model receptor systems providing synthetic receptor cavities for the inclusion of small cationic guests, such as alkali-metal or ammonium ions. [2][3][4][5] Organic cations, such as ammonium ions, play a significant role in molecular recognition processes in nature (e.g. in protein side chains). Calix[n]arenes, generally, are a class of macrocyclic compounds formed by the base-catalyzed condensation of nphenol derivatives and formaldehyde. [2,3] The resorc [4]arenes [6,7] considered herein are calixarenes formed from four

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“…Diese Werte sind vergleichbar mit den berechneten Van-derWaals-Durchmessern von 0.3 nm für den Ammonium-und 0.6 nm für den Trimethylammoniumrest. [9] Es lässt sich also schließen, dass der Passgenauigkeit (sterischen Komplementarität), mit der sich das Gastmolekül in den Rezeptorhohlraum einfügt, eine große Bedeutung bei der Wechselwirkung zukommt, wobei Kation-p-Wechselwirkungen beträcht-lich zum molekularen Bindungsmechanismus beitragen. Dieser Sachverhalt trifft auch für den Trimethylammoniumrest zu, da gezeigt werden konnte, dass an den Wasserstoffatomen der Methylgruppen eine positive Partialladung vorliegt.…”

Section: Angewandte Chemieunclassified