The AAAA·DDDD Hydrogen Bond Dimer. Synthesis of a Soluble Sulfurane as AAAA Domain and Generation of a DDDD Counterpart

2009 ◽  
Vol 62 (11) ◽  
pp. 1550 ◽  
Author(s):  
Jörg Taubitz ◽  
Ulrich Lüning
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Association Constant ◽  
Recognition Site ◽  
Nmr Titration ◽  
Quadruple Hydrogen Bond

Sulfurane 5b with solubility enhancing substituents has been synthesized to be used as an AAAA recognition site in quadruple hydrogen bond heterodimers. A complementary DDDD partner [4b + H+] has been generated from a DDAD domain 4b by protonation. The association constant for the heterodimer complex formation has been determined by NMR titration in chloroform.

Anion effect on alkali ion-crown complex formation in a moderately concentrated solutions: A sensitive probe of hidden interionic interactions operating in dissociating protic solvents

1990 ◽  
Vol 55 (5) ◽  
pp. 1149-1161
Author(s):  
Jiří Závada ◽  
Václav Pechanec ◽  
Oldřich Kocián
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Charge Density ◽  
Macrocyclic Ligand ◽  
Simple Explanation ◽  
Anion Effect ◽  
Protic Solvents ◽  
The Individual ◽  
Alkali Salts ◽  
Alkali Ion

A powerful anion effect destabilizing alkali ion-crown complex formation has been found to operate in moderately concentrated protic (H2O, CH3OH, C2H5OH) solution, following the order HO- > AcO- > Cl- > Br- > NO3- > I- > NCS-. Evidence is provided that the observed effect does not originate from ion-pairing. A simple explanation is provided in terms of concordant hydrogen bond bridges of exalted stability between the gegenions, M+···OR-H···(OR-H)n···OR-H···A-. It is proposed that encapsulation of alkali ion by the macrocyclic ligand leads to a dissipation of the cation charge density destroying its ability to participate in the hydrogen bond bridge. An opposition against the alkali ion-crown complex formation arises accordingly in the solution in dependence on strength of the hydrogen bridge; for a given cation, the hydrogen bond strength increases with increasing anion charge density from NCS- to HO-(RO-). It is pointed out, at the same time, that the observed anion effect does not correlate with the known values of activity coefficients of the individual alkali salts which are almost insensitive to anion variation under the investigated conditions. As a resolution of the apparent paradoxon it is proposed that, in absence of the macrocyclic ligand, the stabilizing (concordant) bonding between the gegenions is nearly balanced by a destabilizing (discordant) hydrogen bonding between the ions of same charge (co-ions). Intrinsic differences among the individual salts are thus submerged in protic solvents and become apparent only when the concordant bonding is suppressed in the alkali ion-crown complex formation.

Simultaneous membrane transport of two active pharmaceutical ingredients by charge assisted hydrogen bond complex formation

2014 ◽  
Vol 5 (9) ◽  
pp. 3449 ◽  
Author(s):  
Hui Wang ◽  
Gabriela Gurau ◽  
Julia Shamshina ◽  
O. Andreea Cojocaru ◽  
Judith Janikowski ◽  
...  
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Membrane Transport ◽  
Active Pharmaceutical Ingredients ◽  
Pharmaceutical Ingredients

A theoretical and experimental investigation of some unusual intermolecular hydrogen-bond IR bands — Appearances can be deceptive

2006 ◽  
Vol 84 (10) ◽  
pp. 1371-1379 ◽  
Author(s):  
Grzegorz Litwinienko ◽  
Gino A DiLabio ◽  
K U Ingold
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Ethylene Oxide ◽  
Potential Energy ◽  
Potential Energy Surfaces ◽  
Intermolecular Hydrogen Bond ◽  
Phenyl Group ◽  
Fermi Resonance ◽  
Energy Surfaces ◽  
Ir Bands

The IR spectra of the O-H stretch for hydrogen bonds (HBs) arising from complex formation between the HB donor (HBD), 4-fluorophenol, and the HB acceptors, peroxides and ethers, frequently show asymmetry that appears to arise from two incompletely resolved bands from two different complexes, but the O-H HB bands with the HBD methanol are symmetric (M. Berthelot, F. Bessau, and C. Laurence. Eur. J. Org. Chem. 925 (1998)). The present studies show that this difference in O-H HB band shapes also is true for other phenols and alcohols. However with ethylene oxide, 4-fluorophenol gives an almost symmetric O-H HB band with a very broad maximum, while alcohols give symmetric O-H HB bands with well-defined maxima. It is shown by experiment that the unusual O-H HB band shapes for the phenols are not due to Fermi resonance and are unrelated to the enthalpies of HB complex formation. Theoretical exploration of the potential energy (PE) surfaces for complexes of 4-fluorophenol and methanol with tert-butyl methyl ether and ethylene oxide reveals that O-H HB band asymmetry or broadness cannot be ascribed to the presence of two different HB complexes. For this ether, the PE surfaces for rotation about the HB and for up-and-down motion of the HBD with respect to the COC plane of the ether are relatively symmetric for methanol, but are strongly asymmetric for 4-fluorophenol, hence the differences in the O-H HB band shapes. The PE surfaces for the epoxide are effectively symmetric, but the PE for rotation about the HB has a single broad minimum for methanol, whereas with 4-fluorophenol there are two minima owing to attractive interactions between the phenyl group and the CH2 groups of the epoxide. The previously unknown β2H values for ethylene oxide and tetramethylethylene oxide are 0.36 and 0.58, respectively.Key words: asymmetric IR O-H bands, asymmetric potential energy surfaces, hydrogen-bonded complexes, hydrogen bond enthalpy, O-H frequency shift.

Solvent-mediated pseudo-quadruple hydrogen-bond motifs in three lamotrigine–carboxylic acid complexes

2013 ◽  
Vol 69 (10) ◽  
pp. 1164-1169 ◽  
Author(s):  
Balasubramanian Sridhar ◽  
Jagadeesh Babu Nanubolu ◽  
Krishnan Ravikumar
Keyword(s):  
Hydrogen Bond ◽  
Hydrogen Bonding ◽  
Carboxylic Acid ◽  
Proton Transfer ◽  
Antiepileptic Drug ◽  
Carboxylic Acids ◽  
Solvent Interactions ◽  
Partial Transfer ◽  
Quadruple Hydrogen Bonding ◽  
Quadruple Hydrogen Bond

Lamotrigine, an antiepileptic drug, has been complexed with three aromatic carboxylic acids. All three compounds crystallize with the inclusion ofN,N-dimethylformamide (DMF) solvent,viz.lamotriginium [3,5-diamino-6-(2,3-dichlorophenyl)-1,2,4-triazin-2-ium] 4-iodobenzoateN,N-dimethylformamide monosolvate, C9H8Cl2N5+·C7H4IO2−·C3H7NO, (I), lamotriginium 4-methylbenzoateN,N-dimethylformamide monosolvate, C9H7Cl2N5+·C8H8O2−·C3H7NO, (II), and lamotriginium 3,5-dinitro-2-hydroxybenzoateN,N-dimethylformamide monosolvate, C9H8Cl2N5+·C7H3N2O7−·C3H7NO, (III). In all three structures, proton transfer takes place from the acid to the lamotrigine molecule. However, in (I) and (II), the acidic H atom is disordered over two sites and there is only partial transfer of the H atom from O to N. In (III), the corresponding H atom is ordered and complete proton transfer has occurred. Lamotrigine–lamotrigine, lamotrigine–acid and lamotrigine–solvent interactions are observed in all three structures and they thereby exhibit isostructurality. The DMF solvent extends the lamotrigine–lamotrigine dimers into a pseudo-quadruple hydrogen-bonding motif.

Interaction of Antitumor Agent Mitoxantrone with Double Helical Synthetic Polyribonucleotides Poly(G)⋅Poly(C) and Poly(I)⋅Poly(C)

2017 ◽  
Vol 12 (04) ◽  
pp. 165-176
Author(s):  
Yuri S. Babayan ◽  
Sergey N. Hakobyan ◽  
Rusanna S. Ghazaryan ◽  
Mariam A. Shahinyan
Keyword(s):  
Complex Formation ◽  
Association Constant ◽  
Antitumor Agent ◽  
Visible Absorption ◽  
Double Stranded Rna ◽  
Base Specificity ◽  
Enthalpy And Entropy ◽  
Uv Visible ◽  
Bromide Interaction ◽  
System Entropy

The interaction of antitumor drug mitoxantrone (MTX) with double-stranded synthetic RNA homopolymers has been studied by means of spectroscopic (UV-Visible absorption, circular dichroism) techniques. The results show a base specificity in this interaction: the association constant with poly(G)[Formula: see text]poly(C) is higher than with poly(I)[Formula: see text]poly(C).Values of changes of the system enthalpy and entropy due to complex-formation were determined through the temperature dependence of the binding constant. Calculations show that due to the intercalation interaction of MTX, the values of changes of the system entropy and enthalpy differ from those obtained at ehtidium bromide interaction with synthetic polyribonucleotides, which shows that the intercalation interaction of MTX with double-stranded RNA significantly differs from that of ethidium bromide with RNA.

scholarly journals Proton transfer equilibria, temperature and substituent effects on hydrogen bonded complexes between chloranilic acid and anilines

2000 ◽  
Vol 14 (3) ◽  
pp. 99-107 ◽  
Author(s):  
Gamal A. Gohar ◽  
Moustafa M. Habeeb
Keyword(s):  
Hydrogen Bond ◽  
Complex Formation ◽  
Proton Transfer ◽  
Equilibrium Constants ◽  
Bond Formation ◽  
Substituent Effects ◽  
Substituted Anilines ◽  
Chloranilic Acid ◽  
Hydrogen Bond Formation ◽  
Linear Relationships

The proton transfer equilibrium constants (KPT) for 1 : 1 complex formation between Chloranilic Acid (CA) and a series ofp- andm‒substituted anilines have been measured in 1,4-dioxane spectrophotometrically. The results supported the concept of amine-solvent hydrogen bond formation (short range solvation effect). Beside, this effect, theKPTvalues were apparently affected by the electron donation power of the aniline ring substituent, which was transmitted to the interaction center via resonance and inductive effects. Linear relationships betweenKPTand σ-Hammett substituent constants, or pKvalues formandpanilines,were obtained verifying the above conclusions. The solute-solvent hydrogen bond formation might increase the reactivity of the aniline nitrogen than would the inductive effect of the alkyl group, in case of CA-N-alkyl aniline complexes. The thermodynamic parameters for the proton transfer complex formation were estimated and it was indicated that the solvent–aniline hydrogen bond formation was preferred in the case ofp-substituted aniline complexes more than in the case of the correspondingm‒isomer. It has been found that the proton transfer process was enthalpy and entropy controlled.

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