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The formation of host–guest complexes between surfactants and cyclodextrins

Valente, Artur J. M.; Söderman, Olle
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.53%
Cyclodextrins are able to act as host molecules in supramolecular chemistry with applications ranging from pharmaceutics to detergency. Among guest molecules surfactants play an important role with both fundamental and practical applications. The formation of cyclodextrin/surfactant host–guest compounds leads to an increase in the critical micelle concentration and in the solubility of surfactants. The possibility of changing the balance between several intermolecular forces, and thus allowing the study of, e.g., dehydration and steric hindrance effects upon association, makes surfactants ideal guest molecules for fundamental studies. Therefore, these systems allow for obtaining a deep insight into the host–guest association mechanism. In this paper, we review the influence on the thermodynamic properties of CD–surfactant association by highlighting the effect of different surfactant architectures (single tail, double-tailed, gemini and bolaform), with special emphasis on cationic surfactants. This is complemented with an assessment of the most common analytical techniques used to follow the association process. The applied methods for computation of the association stoichiometry and stability constants are also reviewed and discussed; this is an important point since there are significant discrepancies and scattered data for similar systems in the literature. In general...

Host-guest interactions between xanthones and water: the role of O-H center dot center dot center dot O, C-H center dot center dot center dot O, and pi center dot center dot center dot pi contacts in the channel- and cage-type frameworks

Correa, Rodrigo S.; dos Santos, Marcelo H.; Nagem, Tanus J.; Ellena, Javier
Fonte: SPRINGER/PLENUM PUBLISHERS; NEW YORK Publicador: SPRINGER/PLENUM PUBLISHERS; NEW YORK
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
66.43%
In this article were studied two xanthone derivatives known as 1,5-dihydroxy-8-methoxyxanthone (I) and 1,3,7-trihydroxy-8-methoxyxanthone (II), which show one water molecule into their crystal structures. In xanthone I, there are water wires contributing to build up channel-like cavities along the c axis, whereas in xanthone II the water is surrounded by three xanthone molecules forming a cage-type structure. The geometries of I and II were optimized using the density functional theory method with B3LYP functional, and the results were compared with crystal structure. Both theoretical and experimental investigations reveal a concordance between structural parameters, with the xanthone core presenting an almost flat conformation and substituents adopting the more stable orientations. In the two compounds, the hydroxyl group linked at position 1 is involved in a resonance-assisted hydrogen bond with the carbonyl group. Besides, the supramolecular arrangement of the host/guest systems are stabilized mainly by classical intermolecular hydrogen bonds (O-H center dot center dot center dot O) involving xanthone-to-water and xanthone-to-xanthone. In addition, C-H center dot center dot center dot O weak hydrogen bonds, as well as pi-pi interactions play an important role to stabilize the crystal self-assembly of xanthones I and II. The results reported here underline the role of inclusion of water molecules and their different arrangement into the crystal structure of two xanthone host/guest systems.; CNPq; CNPq; Capes; CAPES; FAPEMIG (Minas Gerais); FAPEMIG (Minas Gerais); FAPESP (Sao Paulo); FAPESP (Sao Paulo)

Kinetics of photoinduced birefringence in the guest-host system of poly(methyl methacrylate) doped with azobenzene-containing crown ethers

Shimizu, Flavio Makoto; Volpati, Diogo; Giacometti, Jose Alberto; Sworakowski, Juliusz; Janus, Krzysztof; Luboch, Elzbieta
Fonte: Wiley-Blackwell Publicador: Wiley-Blackwell
Tipo: Artigo de Revista Científica Formato: 130-136
ENG
Relevância na Pesquisa
56.33%
The kinetics of the buildup and decay of photoinduced birefringence was examined in a series of host-guest systems: azobenzene-containing crown ethers, differing in the size of the crowns, dissolved in a poly (methyl methacrylate) matrix. In all samples, the kinetics of the buildup of the birefringence was reasonably described by a sum of two exponential functions, the time constants being inversely proportional to the intensity of the pumping light and the magnitudes of the signals at the saturation level depending on the pumping light intensity and sample thickness. The dark decays were best described by the stretched exponential function, with the characteristic parameters (time constant and stretch coefficient) being practically independent of the type of crown ether. The time constants of the signal decay were orders of magnitude shorter than the respective constants of the dark isomerization of the azo crown ethers, thus indicating that the process controlling the decay was a relaxation of the polymer matrix and/or a rearrangement of the flexible parts of the crowns. (C) 2007 Wiley Periodicals, Inc.

Supramolecular recognition: On the kinetic lability of thermodynamically stable host–guest association complexes

Goshe, Andrew J.; Steele, Ian M.; Ceccarelli, Christopher; Rheingold, Arnold L.; Bosnich, B.
Fonte: National Academy of Sciences Publicador: National Academy of Sciences
Tipo: Artigo de Revista Científica
Publicado em 16/04/2002 EN
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46.53%
A molecular receptor consisting of a spacer bearing two cofacially disposed terpyridyl–palladium–ligand (terpy-Pd-L) units rigidly separated by about 7 Å has been investigated for molecular recognition of planar aromatic molecules. It is found that although the receptor forms stable 1:2 host–guest association complexes with 9-methylanthracene (9-MA), the guest undergoes very rapid site exchange within the receptor and with external free 9-MA. A crystal structure of the 2:1 adduct shows one 9-MA in the molecular cleft defined by the two terpy-Pd-L units and the other resides on an outside face of one terpy-Pd-L unit. To establish the site residency time of the guests, a number of tethered molecules were prepared. These involve an anthracene molecule tethered to a pyridine ligand bound to the palladium atoms to form intramolecular host–guest adducts. Rotating-frame Overhauser effects were used to infer the site residency of the anthracene guests in the receptor. Variable-temperature 1H NMR spectroscopy of the intramolecular host–guest complexes has revealed that the site residency time of the anthracene guests is 1.6 × 10−5 sec at 20°C and 1.3 sec at −90°C in acetone solution. Whereas the guests are thermodynamically stable...

A Structural Model of Polyglutamine Determined from a Host-Guest Method Combining Experiments and Landscape Theory

Finke, John M.; Cheung, Margaret S.; Onuchic, José N.
Fonte: Biophysical Society Publicador: Biophysical Society
Tipo: Artigo de Revista Científica
Publicado em /09/2004 EN
Relevância na Pesquisa
46.62%
Modeling the structure of natively disordered peptides has proved difficult due to the lack of structural information on these peptides. In this work, we use a novel application of the host-guest method, combining folding theory with experiments, to model the structure of natively disordered polyglutamine peptides. Initially, a minimalist molecular model (CαCβ) of CI2 is developed with a structurally based potential and captures many of the folding properties of CI2 determined from experiments. Next, polyglutamine “guest” inserts of increasing length are introduced into the CI2 “host” model and the polyglutamine is modeled to match the resultant change in CI2 thermodynamic stability between simulations and experiments. The polyglutamine model that best mimics the experimental changes in CI2 thermodynamic stability has 1), a β-strand dihedral preference and 2), an attractive energy between polyglutamine atoms 0.75-times the attractive energy between the CI2 host Go-contacts. When free-energy differences in the CI2 host-guest system are correctly modeled at varying lengths of polyglutamine guest inserts, the kinetic folding rates and structural perturbation of these CI2 insert mutants are also correctly captured in simulations without any additional parameter adjustment. In agreement with experiments...

Cyclic Tetranuclear and Hexanuclear Palladium(II) Complexes and Their Host-Guest Chemistry

Walmsley, Judith A.; Zhu, Shourong; Matilla, Antonio; Donowick, Tiffanee G.; Cramp, Jessica E.; Tercero, Jose Manuel; Dalrymple, Tatyana
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.57%
Cyclic tetrameric complexes have been prepared by the reaction of Pd(en)Cl2 or Pd(dapol)Cl2, or their nitrato analogs, with Na2(5′GMP) in aqueous solution, where en = 1,2-diaminoethane, dapol = 1,3-diamino-2-propanol, 5′-GMP = guanosine 5′-monophosphate. Addition of certain small molecules containing hydrophobic groups resulted in the expansion of the tetramer to a cyclic hexamer with strong bonding of one guest per hexameric host. At pH 5-6, the guest molecule can be a cation, anion, or neutral, and those species containing trimetylsilyl and t-butyl groups bonded the most strongly. The size of the central cavity of the [Pd(en)(5′GMP)]6 host has been estimated to be 5.2 Ǻ. Formation of the host-guest complex caused a large upfield shift (Δδ) of 2.5-2.9 ppm in the 1H NMR spectrum of the most highly affected guest protons, which were those in closest proximity to the guanine nucleobases. NOESY spectra were used to determine the interaction sites between the host and the guest. Apparent association constants determined at 26 °C and pD 5.4 for the [Pd(en)(5′GMP)]6-DSS and [Pd(en)(5′GMP)]6 -t-butanol systems, where DSS is 3-(trimethylsilyl)-1-propanesulfonate anion, were 1.36 ± 0.11 × 104 and 2.74 ± 0.95 × 104 M−3/2...

The SAMPL4 host–guest blind prediction challenge: an overview

Muddana, Hari S.; Fenley, Andrew T.; Mobley, David L.; Gilson, Michael K.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.55%
Prospective validation of methods for computing binding affinities can help assess their predictive power and thus set reasonable expectations for their performance in drug design applications. Supramolecular host–guest systems are excellent model systems for testing such affinity prediction methods, because their small size and limited conformational flexibility, relative to proteins, allows higher throughput and better numerical convergence. The SAMPL4 prediction challenge therefore included a series of host–guest systems, based on two hosts, cucurbit[7]uril and octa-acid. Binding affinities in aqueous solution were measured experimentally for a total of 23 guest molecules. Participants submitted 35 sets of computational predictions for these host–guest systems, based on methods ranging from simple docking, to extensive free energy simulations, to quantum mechanical calculations. Over half of the predictions provided better correlations with experiment than two simple null models, but most methods underperformed the null models in terms of root mean squared error and linear regression slope. Interestingly, the overall performance across all SAMPL4 submissions was similar to that for the prior SAMPL3 host–guest challenge, although the experimentalists took steps to simplify the current challenge. While some methods performed fairly consistently across both hosts...

Beta-cyclodextrin modification and host-guest complexation.

Pham, Duc-Truc
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2008
Relevância na Pesquisa
66.64%
A series of five linked β-cyclodextrin (βCD) dimers N,N-bis(6 [superscript]A-deoxy-6[superscript]A-β-cyclodextrinyl)-succinamide, 66βCD₂su, N-((2[superscript]A S,3 [superscript]A S)-3 [superscript]A-deoxy-3 [superscript]A-β-cyclodextrinyl)-N’-(6 [superscript]A-deoxy-6 [superscript]A -β-cyclodextrinyl)-urea, 36βCD₂su, N,N-bis((2 [superscript]A S,3 [superscript]A S)-3 [superscript]A -deoxy-3 [superscript]A-β-cyclodextrinyl)-succinamide, 33βCD₂su, N,N-bis(6[superscript]A-deoxy-6[superscript]A-β-cyclodextrinyl)-urea, 66βCD₂ur, and N-((2 [superscript]A S,3 [superscript]A S)-3 [superscript]A-deoxy-3 [superscript]A-β-cyclodextrinyl)-N’-(6 [superscript]A -deoxy-6 [superscript]A -β-cyclodextrinyl)urea, 36βCD₂ur, has been prepared. The complexation of 6-(4’-(toluidinyl)naphthalene-2-sulphonate, TNS⁻, by βCD and the five linked βCD dimers was characterized by UV, fluorescence and 2D ¹H ROESY NMR spectroscopy. In aqueous phosphate buffer at pH 7.0, I = 0.10 mol dm⁻³ and 298.2 K, TNS⁻ forms host-guest complexes with βCD of stoichiometry βCD.TNS⁻ (K₁ = 3020 and 3320 dm³ mol⁻¹) and βCD₂.TNS⁻ (K₂ = 57 and 11 dm³ mol⁻¹) where the first and second values were determined in UV and fluorescence studies...

Supramolecular chemistry of beta- and gamma- cyclodextrin dimers.

Ngo, Huy Tien
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado
Publicado em //2010
Relevância na Pesquisa
46.57%
Native and modified cyclodextrins (CDs) act as robust hosts for a variety of guest species in water, and therefore are at the centre of supramolecular chemistry. Covalently linked CD dimers provide many advantages over native CDs in complexation of guest species in terms of their stability, selectivity or flexibility. The studies underpinning this thesis are based on the β-cyclodextrin dimers, N,N’-bis((2AS,3AS)-3A-deoxy-β-cyclodextrin-3A-yl) succinamide, 33βCD₂suc, and N,N′-bis(6A-deoxy-B-cyclodextrin-6A-yl) succinamide, 66βCD₂suc, and the γ-cyclodextrin dimers, N,N′-bis((2AS,3AS)-3A-deoxy-γ-cyclodextrin-3A-yl) succinamide, 33γCD2suc, and N,N′’-bis(6A-deoxy-γ-cyclodextrin-6A-yl) succinamide, 66γCD2suc, in which the two βCD or γCD cavities are joined together through either the C₃A or C₆A carbons of altropyranose or glucopyranose units, respectively. Often in supramolecular systems, several competing equilibria exist, as exemplified by host–guest complexation and guest aggregation. The complexation of dimerising cationic pyronines B and Y, PB⁺ and PY⁺, by βCD and the βCD dimers, 33βC₂suc and 66βCD₂suc, has been studied by UV–vis, fluorescence and ¹H NMR spectroscopy. The complexation constants for the 1:1 host–guest complexes are reported as are the dimerisation constants for PB⁺ and PY⁺. The modes of complexation...

Tailoring polymeric hydrogels through cyclodextrin host-guest complexation

Guo, X.; Wang, J.; Li, L.; Pham, D.T.; Clements, P.; Lincoln, S.; May, B.; Chen, Q.; Zheng, L.; Prud'homme, R.
Fonte: Wiley-V C H Verlag GMBH Publicador: Wiley-V C H Verlag GMBH
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
66.43%
A close correllation between molecular-level interactions and macroscopic characteristics of polymer networks exists. The characteristics of the polymeric hydrogels assembled from β-cyclodextrin (β-CD) and adamantyl (AD) substituted poly(acrylate)s can be tailored through selective host–guest complexation between β-CD and AD substituents and their tethers. Dominantly, steric effects and competitive intra- and intermolecular host–guest complexation are found to control poly(acrylate) isomeric inter-strand linkage in polymer network formation. This understanding of the factors involved in polymeric hydrogel formation points the way towards the construction of increasingly sophisticated biocompatible materials.; Xuhong Guo, Jie Wang, Li Li, Duc-Truc Pham, Philip Clements, Stephen F. Lincoln, Bruce L. May, Qingchuan Chen, Li Zheng, Robert K. Prud'homme

Steric effects and competitive intra- and intermolecular host-guest complexation between beta-cyclodextrin and adamantyl substituted poly(acrylate)s in water: a 1H NMR, rheological and preparative study

Guo, X.; Wang, J.; Li, L.; Pham, D.T.; Clements, P.; Lincoln, S.; May, B.; Chen, Q.; Zheng, L.; Prud'homme, R.
Fonte: John Wiley & Sons Inc Publicador: John Wiley & Sons Inc
Tipo: Artigo de Revista Científica
Publicado em //2010 EN
Relevância na Pesquisa
66.55%
A 1H NMR and rheological study of host-guest complexation interactions between three -cyclodextrin and three adamantyl substituted poly(acrylate)s, and also between them and adamantan-1-carboxylate and native -cyclodextrin, respectively, is reported. A close correllation between molecular level interactions and macroscopic characteristics of polymer networks in aqueous solution exists. It is found that intra- and intermolecular host-guest complexation between the host -cyclodextrin and guest adamantyl substituents and the length of the aliphatic tether between them and the poly(acrylate) backbone have important roles. Dominantly, steric effects and competitive intra- and intermolecular host-guest complexation are found to control poly(acrylate) isomeric interstrand linkage in polymer network formation. The preparations of five new 3% randomly substituted poly(acrylate)s are reported.; Xuhong Guo, Jie Wang, Li Li, Duc-Truc Pham, Philip Clements, Stephen F. Lincoln, Bruce L. May, Qingchuan Chen, Li Zheng and Robert K. Prud'homme

Host-guest chemistry between cucurbit[7]uril and neutral and cationic guests

WYMAN, IAN
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 7145551 bytes; application/pdf
EN; EN
Relevância na Pesquisa
66.59%
This thesis describes the host-guest chemistry between cucurbit[7]uril (CB[7]) and various series of guests, including neutral polar organic solvents, bis(pyridinium)alkane dications, local anaesthetics, acetylcholine analogues, as well as succinylcholine and decamethonium analogues, in aqueous solution. A focus of this thesis is the effects of varying the chemical structures within different series of guests upon the nature of the host-guest chemistry, such as the relative position and orientation of the guest relative to the CB[7] cavity, and the strengths of the binding affinities. The binding affinities of polar organic solvents with CB[7] depend upon the hydrophobic effect and dipole-quadrupole interactions. The polar guests align themselves so that their dipole moment is perpendicular to the quadrupole moment of CB[7]. The binding strengths of acetone and acetophenone to CB[7] decrease in the presence of alkali metals. Discrete 1:1 and 2:1 host-guest complexes are formed between CB[7] and a series of bis(pyridinium)alkane guests. In most cases the CB[7] initially occupies the aliphatic linker when the 1:1 complex is formed and migrates to the terminal regions as the second CB[7] is added. When bulky, hydrophobic tert-butyl substituents are present...

HOST-GUEST CHEMISTRY BETWEEN CUCURBIT[7]URIL AND CATIONIC AND NEUTRAL GUESTS

MacGillivray, BRENDAN
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
EN; EN
Relevância na Pesquisa
46.65%
This thesis describes the use of electrospray mass spectrometry, 1H NMR, and UV-visible spectroscopy, along with molecular modeling studies, to characterize the host-guest complexes that are formed between the cucurbit[7]uril (CB[7]) host molecule and a series of cationic alkylammonium (benzethonium), biguanidinium (metformin, phenformin, chlorhexidine and alexidine), amidinium (berenil, pentamidine, and 4-hydroxy- and 4-aminobenzamidines), and flavylium (4’- and 6-methoxyflavylium and 6,4’-dimethoxyflavylium) guests in aqueous solution. The stoichiometries and binding strengths of the CB[7] host-guest complexes with these series of drug and dye molecules were determined, and have been rationalized in terms of the specific ion-dipole interactions and hydrophobic effects involved. The potential uses of CB[7] as a slow-release drug delivery agent and molecular stabilizing agent are indicated from kinetic and spectroscopic studies on the reactivities of the host-guest complexes. CB[7] forms 1:1 and 2:1 host-guest complexes with the benzethonium cation by sequential binding to the hydrophilic benzyldimethylammonium group and the hydrophobic 2,4,4-trimethylpentyl group, respectively. The binding strength at the former site is consistent with data for other CB[7]-benzylammonium guests...

HOST-GUEST COMPLEXATION BASED ON CUCURBITURILS

Yuan, Lina
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 2478877 bytes; application/pdf
EN; EN
Relevância na Pesquisa
46.59%
This thesis deals with the effects of host-guest complexation, based on cucurbit[n]uril (CB[n], n = 6, 7 and 8) host molecule, on the chemical, electrochemical and spectroscopic properties of the included guests. Both CB[6] and CB[7] form 1:1 complexes with [CH3bpy(CH2)6bpyCH]4+3, encapsulating the central hexamethylene chain. With its relatively larger cavity, a second CB[7] host will include one of the viologen units, forcing, through steric and electronic repulsions, the first CB[7] to abandon the inclusion of the central chain and move to the other viologen unit, thus forming a [3]pseudorotaxane. The inclusion of the two enantiomers of protonated N-benzyl-1-(1-naphthyl)ethylamine in the achiral CB[7] results in a five-fold increase in the molar optical rotation of {BNEAH•CB[7]}+ and significant changes in the longer wavelength band in the circular dichroism spectra, attributed to a restricted rotation of the naphthyl group about the chiral center upon inclusion of the benzyl portion of the guest in the CB[7] cavity. The effects of host-guest complexation of the (trimethylammonio)- methylferrocene(+/2+) couple (FcTMA+/2+) by CB[7] on the kinetics of its electron self-exchange and electron transfer reactions were investigated. The slow exchange of the ferrocene guest...

Cucurbit[n]uril host-guest complexes: the effects of inclusion on the chemical reactivity and spectroscopic properties of aromatic guest molecules

Wang, Ruibing
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado Formato: 3935091 bytes; application/pdf
EN; EN
Relevância na Pesquisa
66.61%
This thesis deals primarily with supramolecular chemistry based on cucurbit[n]uril (CB[n], n = 7 and 8) host molecules. The research has been focused on the synthesis and characterization of host-guest complexes CB[n] with aromatic guest molecules, and the study of the effects of the host-guest complexation on the chemical reactivity and spectroscopic properties of the included guests, such as their photoreactivity and their UV-visible absorption and emission properties, in aqueous solution. The [4+4] photodimerization of protonated 2-aminopyridine (APH+) occurs stereoselectively to give the anti-trans product as the result of a preferred orientation of two APH+ guests in the cavity of CB[7]. The CB[7] host inhibits photohydration in the course of the photoisomerizations of protonated trans-1,2-bis(4-pyridyl)ethylene and trans-1,2-bis(1-methyl-4-pyridinium)ethylene by including the (4-pyridyl)ethylene portion of the guest, while this is not observed with trans-1,2-bis(1-hexyl-4-pyridinium)ethylene, as preferential inclusion of the hexyl groups leaves the vinyl group vulnerable to photohydration. Very strong CB[7] complexation of (E)-1-ferrocenyl-2-(1-methyl-4-pyridinium)ethylene completely inhibits the (E)→(Z) photoisomerization process. The H/D exchange rates and acidities of the C(2)-proton of cationic imidazolium and thiazolium (including thiamine and thiamine phosphates) carbon acids are decreased upon their complexation with CB[7]. Inclusion of protonated aromatic amines (and aromatic alcohols) in the cavity CB[7] significantly decreases their ground and excited state acidities...

Incommensurate host-guest structures in compressed elements: Hume-Rothery effects as origin

Degtyareva, Valentina F
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/10/2015
Relevância na Pesquisa
46.59%
Discovery of the incommensurate structure in the element Ba under pressure 15 years ago was followed by findings of a series of similar structures in other compressed elements. Incommensurately modulated structures of the host-guest type consist of a tetragonal host structure and a guest structure. The guest structure forms chains of atoms embedded in the channels of host atoms so that the axial ratio of these subcells along the c axis is not rational. Two types of the host-guest structures have been found so far: with the host cells containing 8 atoms and 16 atoms; in these both types the guest cells contain 2 atoms. These crystal structures contain a non-integer number of atom in their unit cell: tI11* in Bi, Sb, As, Ba, Sr, Sc and tI19* in Na, K, Rb. We consider here a close structural relationship of these host-guest structures with the binary alloy phase Au3Cd5-tI32. This phase is related to the family of the Hume-Rothery phases that is stabilized by the Fermi sphere - Brillouin zone interaction. From similar considerations for alkali and alkaline-earth elements a necessary condition for structural stability emerges in which the valence electrons band overlaps with the upper core electrons and the valence electron count increases under compression.; Comment: 8 pages...

Topological Analysis of Void Spaces in Tungstate Frameworks: Assessing Storage Properties for the Environmentally Important Guest Molecules and Ions: CO_2, UO_2, PuO_2, U, Pu, Sr^2+, Cs+, CH_4, and H_2

Cole, Jacqueline Manina; Cramer, Alisha J.; Zeidler, Anita
Fonte: ACS Publicador: ACS
Tipo: Article; accepted version
EN
Relevância na Pesquisa
56.45%
This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acssuschemeng.5b00369; The identification of inorganic materials, which are able to encapsulate environmentally important small molecules or ions via host-guest interactions, is crucial for the design and development of next-generation energy sources and for storing environmental waste. Especially sought after are molecular sponges with the ability to incorporate CO2, gas pollutants, or nuclear waste materials such as UO2 and PuO2 oxides or U, Pu, Sr2+ or Cs+ ions. Porous framework structures promise very attractive prospects for applications in environmental technologies, if they are able to incorporate CH4 for biogas energy applications, or to store H2, which is important for fuel cells e.g. in the automotive industry. All of these applications should benefit from the host being resistant to extreme conditions such as heat, nuclear radiation, rapid gas expansion, or wear and tear from heavy gas cycling. As inorganic tungstates are well known for their thermal stability, and their rigid open-framework networks, the potential of Na2O-Al2O3-WO3 and Na2O-WO3 phases for such applications was evaluated. To this end, all known experimentally-determined crystal structures with the stoichiometric formula MaM?bWcOd (M = any element) are surveyed together with all corresponding theoretically calculated NaaAlbWcOd and NaxWyOz structures that are statistically likely to form. Network descriptors that categorize these host structures are used to reveal topological patterns in the hosts...

Aqueous Desolvation and Molecular Recognition: Experimental and Computational Studies of a Novel Host-Guest System Based on Cucurbit[7]uril

Wang, Yi
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2012
Relevância na Pesquisa
56.26%

Molecular recognition is arguably the most elementary physical process essential for life that arises at the molecular scale. Molecular recognition drives events across virtually all length scales, from the folding of proteins and binding of ligands, to the organization of membranes and the function of muscles. Understanding such events at the molecular level is massively complicated by the unique medium in which life occurs: water. In contrast to recognition in non-aqueous solvents, which are driven largely by attractive interactions between binding partners, binding reactions in water are driven in large measure by the properties of the medium itself. Aqueous binding involves the loss of solute-solvent interactions (desolvation) and the concomitant formation of solute-solute interactions. Despite decades of research, aqueous binding remains poorly understood, a deficit that profoundly limits our ability to design effective pharmaceuticals and new enzymes. Particularly problematic is understanding the energetic consequences of aqueous desolvation, an area the Toone and Beratan groups have considered for many years.

In this dissertation, we embark on a quest to shed new light on aqueous desolvation from two perspectives. In one component of this research...

Molecular Recognition in Host-Guest Ionophore-Siderophore Assemblies

Tristani, Esther Marie
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação Formato: 29967873 bytes; application/pdf
Publicado em //2010 EN_US
Relevância na Pesquisa
56.68%

This work examines the characterization of supramolecular assemblies and, more specifically, host-guest complexes involved in molecular recognition events. The supramolecular assemblies studied take root from metal ion delivery in biological uptake pathways, specifically the delivery of iron to microbial cells. These assemblies are studied in an effort to further understand the nature of molecular recognition events, specifically the nature and strength of interactions between a host and a guest, and possible applications of these systems.

The development of a mass spectral method by which to characterize supramolecular assemblies involving the cation binding hosts 18-crown-6, benzo-18-crown-6, dicyclohexano-18-crown-6, and dibenzo-18-crown-6 macrocycles, and the linear ionophore lasalocid with cationic guests, including substituted protonated amines and the iron siderophore ferrioxamine B is presented. Methodology was developed using ESI-MS to successfully quantitate host-guest interactions in binary and complex mixtures. Binding constants were obtained in the range of log Ka = 3 - 5 and correspond to similar systems previously studied in the literature. The studies presented here further our understanding of the molecular recognition events that must occur between a siderophore and a receptor and provide an improved method by which to measure the strength of their interaction.

The effects of redox hosts on host-guest complex formation with ferrioxamine B and the characterization of the host-guest complexes formed and the strength of the interactions between them were studied using cyclic voltammetry...

A simple polarimetry technique for predicting the absolute configuration of the preferred enantiomer in chiral host-guest inclusion complexes

Barton,Benita; Pohl,Pieter
Fonte: South African Journal of Chemistry Publicador: South African Journal of Chemistry
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
66.53%
A method for predicting the configuration of the preferred guest enantiomer in an inclusion complex with an optically pure hosl compound was developed. The method involves simply measuring the optical rotation of the host-guest inclusion complex as a whole, by means of polarimetry, and using this value in a calculation in order to obtain information about the guest configuration. The availability of standard optically pure guest materials is not required, nor is the isolation of the guest species from the host crystal, resulting in an attractive, inexpensive, rapid and simple procedure for this purpose.