Stabilization of a Reactive Cationic Species by Supramolecular Encapsulation

Ziegler, Marco; Brumaghim, Julia L.; Raymond, Kenneth N.

doi:10.1002/1521-3773(20001117)39:22<4119::aid-anie4119>3.0.co;2-1

Cited by 210 publications

(128 citation statements)

References 21 publications

(24 reference statements)

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“…The examples shown here demonstrate that hostguest complexes containing both weak binding guests as well as sterically demanding guests can be analyzed using electrospray mass spectrometry. This opens up the possibility of using mass spectrometry to study reactive reaction intermediates stabilized via encapsulation [10,21,22], as well as giving insight into catalytic reaction pathways [23], both of which occur inside the cavity. It will also allow for using mass spectrometry as a screening technique to monitor the competitive binding of various guest molecules at lower concentrations than previously observable by NMR spectroscopy.…”

Section: Discussionmentioning

confidence: 99%

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Andersen

Seeber

Fiedler

et al. 2006

J. Am. Soc. Mass Spectrom.

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Self-assembled supramolecular host-guest complexes have been characterized by electrospray ionization mass spectrometry. The spectra obtained by use of a Q-TOF instrument equipped with a Z-spray ion source show primarily the 3-and 4-charge states of the assemblies. The assemblies have the general formula [guest ʚ Ga 4 L 6 ] 11Ϫ where L represents the chelating bidentate catechol ligand 1,5-bis(2=,3=-dihydroxy-benzamido)naphthalene and guests are tetramethyl ammonium (Me 4 N ϩ ), tetraethyl ammonium (Et 4 N ϩ ), tetra-n-propyl ammonium (Pr 4 N ϩ ) and decamethylcobaltocenium (Cp* 2 Co ϩ ) cations. For the first time, the mass spectrum of the empty assembly [Ga 4 L 6 ] 12Ϫ is reported. This article also reports that provided the electrospray ion source is capable of preserving noncovalent interactions, it is possible to observe host-guest complexes containing both weak binding guests as well as sterically demanding guests in the mass spectra. The present data suggest that electrospray mass spectrometry is a powerful tool for characterization of supramolecular host-guest complexes. ( I n the area of supramolecular chemistry, metal-ligand interactions have been exploited to design highly symmetric closed shell structures that selfassemble from simple metal and ligand components. The formation of discrete molecular architectures relies on labile coordinative bonds that allow for self-correction and exclusive formation of the thermodynamic product. A great variety of self-assembled structures of different molecular sizes and shapes is present in the literature [1][2][3][4][5]. Here, we focus on contributions to this field made by Raymond and coworkers [2, 6 -10]. The common theme in these metal-ligand assemblies is the presence of chelating bidentate catechol amide ligands, which bear certain geometric constraints upon coordination to octahedral metal centers resulting in M 4 L 6 coordination tetrahedra (Figure 1). The complexes are highly charged, rendering them soluble in polar solvents such as water and methanol, yet contain hydrophobic cavities of variable sizes. The presence of these hydrophobic cavities affords rich host-guest chemistry, enabling encapsulation of monocationic guest molecules [2, 6 -8]. Several analytical methods are necessary to efficiently characterize these host-guest complexes. 1 H-NMR spectroscopy shows remarkable upfield shifts in the proton signals of encapsulated guests within the cavities [2]. However, since the structures exhibit high point symmetry and the metal components are often paramagnetic, complete characterization by NMR is not always possible. Although solid-state structures may, in the best of cases, be determined by single crystal X-ray crystallography, intrinsically labile metal-ligand interactions do not always allow for unambiguous characterization of solution state structures. Additionally, mass spectrometry is more sensitive than NMR spectroscopy and allows analysis of lower concentrations, thus observing species with solubility properties insufficient for NMR measureme...

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Section: Discussionmentioning

confidence: 99%

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Andersen

Seeber

Fiedler

et al. 2006

J. Am. Soc. Mass Spectrom.

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“…For example, we have demonstrated the synthesis and stabilization of a reactive phosphonium-acetone adduct within the M 4 L 6 cavity in aqueous solution (27). The free adduct degrades rapidly in aqueous solution and would not be observed to form in water without the protection of the hydrophobic cavity of the molecular tetrahedron.…”

Section: Host-guest Chemistry and Nanoscale Reaction Vesselsmentioning

confidence: 98%

“…The use of supramolecular assemblies as reaction vessels is emerging as a new direction in the field (27)(28)(29)(30)(31)(32). The hostguest properties of each assembly dictate which chemical reactions will be suited for transfer from macroscale to nanoscale containers.…”

Section: Host-guest Chemistry and Nanoscale Reaction Vesselsmentioning

confidence: 99%

Supramolecular assembly dynamics

Davis

Yeh²,

Raymond³

2002

Proc. Natl. Acad. Sci. U.S.A.

226

132

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“…[65][66][67] Recently, Warmuth et al reported the generation and stabilization of cycloheptatetraene inside the cavity of a hemicarcerand, 68,69 and reactive cations have been stabilized by trapping them inside a tetrahedral gallium-ligand cluster. 70 Similarly, gases such as NO 2 have been chemically "fixated" and utilized as stable nitrosation reagents by encapsulating them within calixarenes. [71][72][73] …”

Section: Covalent Systemsmentioning

confidence: 99%

Self‐Assembled Nanoreactors

et al. 2005

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Stabilization of a Reactive Cationic Species by Supramolecular Encapsulation

Cited by 210 publications

References 21 publications

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Supramolecular assembly dynamics

Self‐Assembled Nanoreactors

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Stabilization of a Reactive Cationic Species by Supramolecular Encapsulation

Cited by 210 publications

References 21 publications

Characterization of self-assembled supramolecular [Ga4L6] host-guest complexes by electrospray ionization mass spectrometry

Characterization of self-assembled supramolecular [Ga4L6] host-guest complexes by electrospray ionization mass spectrometry

Supramolecular assembly dynamics

Self‐Assembled Nanoreactors

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Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry

Characterization of self-assembled supramolecular [Ga₄L₆] host-guest complexes by electrospray ionization mass spectrometry