Molecular beads on a charged molecular string: α,ω-alkyldiammonium complexes of cucurbit[6]uril in the gas phase

Zhang, Haizhen; Ferrell, Tyler A.; Asplund, Matthew C.; Dearden, David V.

doi:10.1016/j.ijms.2007.02.002

Cited by 38 publications

(38 citation statements)

References 16 publications

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“…In the present study, for the first time, we report on the noncovalent interaction of CB [6] with anionic molecules on its exterior, and their chemical reactions in the gas phase using electrospray ionization mass spectrometry (ESI-MS). ESI-MS is a proven technology to study the intrinsic chemistry of supramolecular complexes in the absence of solvent effects [19], including host-guest chemistry of CB[n] supramolecular complexes [20][21][22][23][24][25]. Especially, interfacing ion mobility spectrometry with ESI-MS has become a powerful tool for screening the structures of supramolecular complexes [26][27][28][29][30].…”

mentioning

confidence: 99%

Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

Choi

Heo

et al. 2012

J. Am. Soc. Mass Spectrom.

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Noncovalent interactions of cucurbit [6]uril (CB[6]) with haloacetate and halide anions are investigated in the gas phase using electrospray ionization ion mobility mass spectrometry. Strong noncovalent interactions of monoiodoacetate, monobromoacetate, monochloroacetate, dichloroacetate, and trichloroacetate on the exterior surface of CB [6] are observed in the negative mode electrospray ionization mass spectra. The strong binding energy of the complex allows intramolecular S N 2 reaction of haloacetate, which yields externally bound CB[6]-halide complex, by collisional activation. Utilizing ion mobility technique, structures of exteriorly bound CB[6] complexes of haloacetate and halide anions are confirmed. Theoretically determined low energy structures using density functional theory (DFT) further support results from ion mobility studies. The DFT calculation reveals that the binding energy and conformation of haloacetate on the CB[6] surface affect the efficiency of the intramolecular S N 2 reaction of haloacetate, which correlate well with the experimental observation.

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mentioning

confidence: 99%

Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

Choi

Heo

et al. 2012

J. Am. Soc. Mass Spectrom.

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“…Analogous reorientations of remote groups in ion-molecule complexes have been reported by Longevialle to occur in ion dissociations of bifunctional steroids [53][54][55][56], and the phenomenon has been analyzed by Morton [57,58]. We investigated a "bead-on-the-string" mechanism [7] in which the alkanediamine chain slides through the (DBCE ϩ H) · ligand and thus brings it close to the opposite ammonium end to displace the DBCE ligand. We used Ar instead of an alkylamine chain because Ar has a similar van der Waals radius (1.88 Å) as methylene and amino groups (1.89 and 1.76 Å, respectively) [59], and the calculations were aided by symmetry.…”

Section: Electronic Properties Of Dbce-ammonium Complexes and Dissocimentioning

confidence: 79%

Host-guest hydrogen atom transfer induced by electron capture

Hao

Tureček

2008

J. Am. Soc. Mass Spectrom.

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1,n-Alkanediammonium cations in noncovalent complexes with two dibenzo-18-crown-6-ether (DBCE) ligands undergo an unusual intramolecular tandem hydrogen atom and proton transfer to the crown ether ligand upon charge reduction by electron capture. Deuterium labeling established that both migrating hydrogens originated from the ammonium groups. The double hydrogen transfer was found to depend on the length of the alkane chain connecting the ammonium groups. Ab initio calculations provided structures for select alkanediammonium.dibenzo-18-crown-6-ether complexes and dissociation products. This first observation of an intra-complex hydrogen transfer is explained by the unusual electronic properties of the complexes and the substantial hydrogen atom affinity of the aromatic rings in the crown ligand.

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“…[25] This inconsistency between the calculated gasphase data and experimental solution-phaser esults triggered us to more carefullyc onsider the solvation effect, especially toward the a/b-anomer discriminationb yC B [7].I ndeed, recent literatureh as documented differentb inding behaviors in the gas and solution phases for CB[n]c omplexes. [41][42][43][44] In the gas phase, bindingp roperties mostly depend on the direct hostguest interactions, whereas in solution they are strongly affected by the mediation of water molecules. [45][46][47] Because amino saccharides have multiple hydrophilic groups that can form hydrogen bonds with water molecules, the interaction with water may dominate the host-guest complex formationm echanism ande nergetics.…”

Section: Gas-phase Structures and Bindingfree Energiesmentioning

confidence: 99%

How Does Solvation Affect the Binding of Hydrophilic Amino Saccharides to Cucurbit[7]uril with Exceptional Anomeric Selectivity?

Wang

Jang

Khedkar

et al. 2016

Chemistry A European J

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Cucurbit[7]uril (CB[7]) is known to bind strongly to hydrophilic amino saccharide guests with exceptional α-anomer selectivities under aqueous conditions. Single-crystal X-ray crystallography and computational methods were used to elucidate the reason behind this interesting phenomenon. The crystal structures of protonated galactosamine (GalN) and glucosamine (GluN) complexes confirm the inclusion of α anomers inside CB[7] and disclose the details of the host-guest binding. Whereas computed gas-phase structures agree with these crystal structures, gas-phase binding free energies show preferences for the β-anomer complexes over their α counterparts, in striking contrast to the experimental results under aqueous conditions. However, when the solvation effect is considered, the binding structures drastically change and the preference for the α anomers is recovered. The α anomers also tend to bind more tightly and leave less space in the CB[7] cavity toward inclusion of only one water molecule, whereas loosely bound β anomers leave more space toward accommodating two water molecules, with markedly different hydrogen-bonding natures. Surprisingly, entropy seems to contribute significantly to both anomeric discrimination and binding. This suggests that of all the driving factors for the strong complexation of the hydrophilic amino saccharide guests, water mediation plays a crucial role in the anomer discrimination.

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Molecular beads on a charged molecular string: α,ω-alkyldiammonium complexes of cucurbit[6]uril in the gas phase

Cited by 38 publications

References 16 publications

Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

Unusual Complex Formation and Chemical Reaction of Haloacetate Anion on the Exterior Surface of Cucurbit[6]uril in the Gas Phase

Host-guest hydrogen atom transfer induced by electron capture

How Does Solvation Affect the Binding of Hydrophilic Amino Saccharides to Cucurbit[7]uril with Exceptional Anomeric Selectivity?

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