Matrix Effects on the Chiral Recognition Determined by the Relative Peak Intensity of Diastereomeric Host-Guest Complex Ions Using the FAB Mass Spectrometry/Enantiomer Labeled Guest Method.

The 1:1 inclusion complex of β-cyclodextrin (βCD) with 5-methoxytryptamine (5MTA) hydrochloride was studied by mass spectrometry (MS) and tandem-MS with fast atom bombardment (FAB), electrospray (ES) and ionspray (IS) ionisation and triple quadrupole or ion trap analysers. A protonated 1:1 βCD/MTA gaseous association was always observed; the protonated species of deaminated 5MTA and of some typical βCD fragments were obtained, in addition to the expected protonated 5MTA, as tandem-MS dissociation products. A reaction pattern starting from the deamination of protonated 5MTA, as a recently described high pressure chemical ionisation or ES process of primary amines, was suggested, which accounts for the formation of excited protonated βCD and its fragmentation by tandem-MS, even under unimolecular conditions.

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Cucurbit[7]uril host-guest complexes with cationic bis(4,5-dihydro-1H-imidazol-2-yl) guests in aqueous solution

Canadian Journal of Chemistry ◽

10.1139/v06-099 ◽

2006 ◽

Vol 84 (6) ◽

pp. 905-914 ◽

Cited By ~ 22

Author(s):

D Saroja N Hettiarachchi ◽

Donal H Macartney

Keyword(s):

Mass Spectrometry ◽

Aqueous Solution ◽

Nmr Spectroscopy ◽

Stability Constants ◽

Electrospray Mass Spectrometry ◽

Hydrophobic Core ◽

Guest Complex ◽

H Nmr ◽

Host Guest Complex ◽

Proton Resonances

The host–guest interactions between cucurbit[7]uril and a series of novel cationic bis(4,5-dihydro-1H-imidazol-2-yl)arene and 1-(4,5-dihydro-1H-imidazol-2-yl)- and 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)-adamantane guests have been investigated in aqueous solution using UV–vis and NMR spectroscopy, and electrospray mass spectrometry. With the exception of the 1,3-bis(4,5-dihydro-1H-imidazol-2-yl)adamantane (which binds externally to the CB[7]), these guests form very stable inclusion complexes with slow exchange on the 1H NMR timescale. The direction and magnitude of the complexation-induced shifts (CIS) in the proton resonances of the guests are indicative of the residence of the hydrophobic core of the guest within the CB[7] cavity and the charged 4,5-dihydro-1H-imidazol-2-yl units outside the cavity adjacent to the carbonyl-lined portals of the host. The CIS values and the inclusion stability constants have been correlated with the nature of the guest core and with the distance between the charges on the terminal 4,5-dihydro-1H-imidazol-2-yl rings.Key words: cucurbit[7]uril, host–guest complex, dihydroimidazolyl, inclusion stability constants.

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A study of formation and fragmentation of ionic metal complexes of substituted benzoic and cinnamic acids with Al(III)–glycerol by fast atom bombardment mass spectrometry

Canadian Journal of Chemistry ◽

10.1139/v97-045 ◽

1997 ◽

Vol 75 (4) ◽

pp. 398-404

Author(s):

Mandapati Saraswathi ◽

Jack M. Miller

Keyword(s):

Mass Spectrometry ◽

Carboxylic Acid ◽

Metal Complexes ◽

Spectral Data ◽

Fast Atom Bombardment ◽

Complex Ions ◽

Cinnamic Acids ◽

Collisionally Activated Dissociation ◽

Fab Mass Spectrometry

Substituted benzoic and cinnamic acids were studied by FAB mass spectrometry using matrix-based Al(III) ions. Complex ions derived from these acids, such as ( M + 117 )+ ( 117 = (Al + glycerol − 2H)+ ), ( M + 159 )+ ( 159 = [2Al + 2glycerol − 5H − 74(epoxypropanol)]+), and ( M + 233)+ ( 233 = (2Al + 2glycerol − 5H)+), when subjected to collisionally activated dissociation (CAD), gave an ion corresponding to ( M − OH)+. Formation of this ion was explained by the transfer of the carboxylic -OH group to the ( Al + glycerol − 2H)+, ( 2Al + 2glycerol − 5H − 74 )+, and ( 2Al + 2glycerol − 5H )+ portion of the complexes. This transfer is more pronounced in the case of meta- and para-substituted acids. The CAD of the ( M + 117 )+ ions yielded ( M + Al(III) )+ ions resulting from the insertion of Al(III) into the carboxylic acid, which was followed by the elimination of CO to produce ( M + Al(III) − CO)+ ions. Interpretation of spectral data was clarified by study of the formation and fragmentation of ions produced from deuterated benzoic and cinnamic acids. Keywords: substituted benzoic and trans-cinnamic acids, Al(III)–glycerol, FAB mass spectrometry, ionic metal complexes, collisionally induced dissociation, Al(III) insertion, carbonyl cations.

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Metalloporphyrin Dimers Bridged by a Peptoid Helix: Host-Guest Interaction and Chiral Recognition

Molecules ◽

10.3390/molecules23112741 ◽

2018 ◽

Vol 23 (11) ◽

pp. 2741 ◽

Cited By ~ 7

Author(s):

Yen Lee ◽

Boyeong Kang ◽

Jiwon Seo

Keyword(s):

Drug Delivery ◽

Molecular Recognition ◽

Complex Formation ◽

Asymmetric Catalysis ◽

Spectroscopic Data ◽

Chiral Recognition ◽

Guest Complex ◽

Molecular Sensing ◽

Host Guest Complex ◽

Chirality Induction

Co-facial porphyrins have been designed to construct porphyrin tweezers with versatile molecular recognition capabilities. In this study, we synthesized metalloporphyrin–peptoid conjugates (MPPCs) displaying two metalloporphyrins on a peptoid scaffold with either achiral unfolded (1) or helical (2 and 3) secondary structures. Host–guest complexation of MPPCs was realized with various guests of different lengths and basicities, and the extent of complexation was measured by UV-vis and circular dichroism (CD) spectroscopic titration. Intermolecular and intramolecular chirality induction were observed on achiral and chiral peptoid backbones, respectively. Spectroscopic data indicated that a broad scope of achiral guests can be recognized by chiral 2; in particular, longer and more flexible guests were seen to bind more tightly on 2. In addition, chiral 2 provided a distinct CD couplet with dl-, d-, or l-Lys-OMe, which was a result of the diastereomeric host–guest complex formation. Our results indicated that MPPCs can recognize, contrast, and analyze various achiral, chiral, or racemic molecules. Based on co-facial metalloporphyrins present on peptoid scaffolds, we developed a novel class of porphyrin tweezers, which can be further utilized in asymmetric catalysis, molecular sensing, and drug delivery.

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