VT <sup>1</sup>H NMR Investigations of Resonance-Assisted Intramolecular Hydrogen Bonding in 4-(Dimethylamino)-2‘-hydroxychalcone

Wachter-Jurcsak, Nanette; Detmer, Charles A.

doi:10.1021/ol990770j

Cited by 15 publications

(6 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The 1 H NMR spectra of 1 and 2 in toluene- d 8 at 25 °C contain OH hydrogen peaks at 8.8 and 8.3 ppm, respectively. Their low magnetic field positions are ascribed to intramolecular hydrogen bonding in the complexes, similar to the reported platina- and palladasilsesquioxane complexes. − As can be expected, the signals are shifted to low magnetic field with decreasing temperature and reach 11.6 ppm ( 1 ) and 10.1 ppm ( 2 ) at −80 °C. Change of the concentration of 1 from 40 mM to 5 mM at 25 °C causes a shift of the OH hydrogen peak from 8.54 ppm to 8.23 ppm.…”

Section: Resultssupporting

confidence: 84%

Synthesis and Characterization of Platinasilsesquioxane Complexes and Their Reaction with Arylboronic Acid

2010

View full text Add to dashboard Cite

Phenyl(iodo)platinum complexes having a 2,2 0bipyridine (bpy) or 1,2-bis(diphenylphosphino)ethane (dppe) ligand react with incompletely condensed silsesquioxane (c-C 5 H 9 ) 7 Si 7 O 9 (OH) 3 in the presence of Ag 2 O to yield platinasilsesquioxane complexes [Pt{(c-C 5 H 9 ) 7 Si 7 O 10 (OH) 2 }(C 6 H 5 )-(L)] (1, L = bpy; 2, L = dppe). NMR spectroscopy revealed their square-planar structures with an O-coordinated silsesquioxanate ligand and O-H 3 3 3 O hydrogen bonds within the ligand. Both complexes undergo transmetalation of p-methoxyphenylboronic acid to afford unsymmetrical diarylplatinum complexes [Pt(C 6 H 4 OCH 3 -p)(C 6 H 5 )(L)] (3, L=bpy; 4, L=dppe).

show abstract

Section: Resultssupporting

confidence: 84%

Synthesis and Characterization of Platinasilsesquioxane Complexes and Their Reaction with Arylboronic Acid

2010

View full text Add to dashboard Cite

show abstract

“…13 The chemical shifts for the protons involved in the intramolecular hydrogen bonds are temperature-dependent. 37 This is also the case for the enolimine forms studied. The signal of the hydroxy proton moves downfield as the temperature is lowered (Table 5).…”

Section: Temperature Effect On Tautomeric Equilibriamentioning

confidence: 61%

Substituent and temperature controlled tautomerism of 2-phenacylpyridine: the hydrogen bond as a configurational lock of (Z )-2-(2-hydroxy-2-phenylvinyl)pyridine

Kolehmainen

Ośmiałowski²,

Nissinen

et al. 2000

J. Chem. Soc., Perkin Trans. 2

View full text Add to dashboard Cite

2-Phenacylpyridines substituted in the benzene ring are in equilibrium with (Z)-2-(2-hydroxy-2-phenylvinyl)pyridines when dissolved in chloroform. The substituent affects significantly the tautomeric equilibrium [the amount of the enolimine form stabilized by the intramolecular hydrogen bond is 1 and 92% for R = p-N(CH 2 ) 4 and p-NO 2 , respectively]. The negative logarithm of the tautomeric equilibrium constant, K T , is linearly dependent on the Hammett σ substituent constants. The dependence of K T vs. temperature is exponential in character: the more electronwithdrawing is the substituent, the more distinct is the influence of temperature. Unexpectedly, the tautomer present in the crystalline state is not the same for all compounds studied (it is the ketimine one for those carrying strong electron-donor groups). Among the different ab initio methods used to calculate the enthalpy of the proton transfer in chloroform solution, MP2/6-31G** gives the best results.

show abstract

“…Experimental evidence of the involvement of NH amide protons in intramolecular hydrogen bonds can be obtained from the temperature coefficients of the amide protons (Δδ/Δ T ) . These measurements were widely used to study conformational changes induced by intramolecular hydrogen bonds in peptides and protein. , In fact, the NH group sheltered from its environment at low temperature, will become exposed to the solvent when the temperature increase . Strong variations (Δδ/Δ T ≥ −4.6 ppb K −1 ) indicate low solvent accessibility of the amide protons and, hence, of their involvement in intramolecular hydrogen bonds, although other factors have to be taken into account .…”

Section: Resultsmentioning

confidence: 99%

Anion Recognition by a Macrobicycle Based on a Tetraoxadiaza Macrocycle and an Isophthalamide Head Unit

Bernier

Carvalho

et al. 2009

J. Org. Chem.

View full text Add to dashboard Cite

A macrobicycle formed by a tetraoxadiaza macrocycle containing a dibenzofuran (DBF) spacer and an isophthalamide head unit, named DBF-bz, was used as receptor for anion recognition. The molecular structure of DBF-bz was established in solution by NMR and ESI-MS spectroscopies and in single crystal by X-ray diffraction analysis. The X-ray structure showed a water molecule encapsulated into the macrobicyclic cavity by four hydrogen bonds, two of them involving the two N-H amide binding sites and the oxygen of the water molecule (N-H...O hydrogen bonds) and the other two (O-H...N) involving the amine groups as hydrogen bonding acceptors. (1)H NMR temperature dependence studies demonstrated that the same structure exists in solution. The ability of this ditopic receptor to recognize alkali halide salts was evaluated by extraction studies followed by (1)H NMR and ESI-MS spectroscopies. The macrobicycle showed a capacity to extract halide salts from aqueous solutions into organic phases. The binding ability of this macrobicycle for halides was also quantitatively investigated using (1)H NMR titrations in CDCl(3) (and DMSO-d(6)) solution, and in acidic D(2)O solution. The largest binding association constant was found for the chloride anion and the completely protonated receptor. The results suggest that the diammonium-diamide unit of the receptor strongly bind the anionic substrate via multiple N-H...Cl(-) hydrogen bonds and electrostatic interactions. The binding trend follows the order Cl(-) > Br(-) > I(-) approximately F(-) established from the best fit between the size of the anion and the cavity size of the protonated macrobicycle. Molecular dynamics (MD) simulations of the DBF-bz in CHCl(3) solution allowed a detailed insight into the structural and binding properties of the receptor.

show abstract

VT ¹H NMR Investigations of Resonance-Assisted Intramolecular Hydrogen Bonding in 4-(Dimethylamino)-2‘-hydroxychalcone

Cited by 15 publications

References 14 publications

Synthesis and Characterization of Platinasilsesquioxane Complexes and Their Reaction with Arylboronic Acid

Synthesis and Characterization of Platinasilsesquioxane Complexes and Their Reaction with Arylboronic Acid

Substituent and temperature controlled tautomerism of 2-phenacylpyridine: the hydrogen bond as a configurational lock of (Z )-2-(2-hydroxy-2-phenylvinyl)pyridine

Anion Recognition by a Macrobicycle Based on a Tetraoxadiaza Macrocycle and an Isophthalamide Head Unit

Contact Info

Product

Resources

About

VT 1H NMR Investigations of Resonance-Assisted Intramolecular Hydrogen Bonding in 4-(Dimethylamino)-2‘-hydroxychalcone

Cited by 15 publications

References 14 publications

Synthesis and Characterization of Platinasilsesquioxane Complexes and Their Reaction with Arylboronic Acid

Synthesis and Characterization of Platinasilsesquioxane Complexes and Their Reaction with Arylboronic Acid

Substituent and temperature controlled tautomerism of 2-phenacylpyridine: the hydrogen bond as a configurational lock of (Z )-2-(2-hydroxy-2-phenylvinyl)pyridine

Anion Recognition by a Macrobicycle Based on a Tetraoxadiaza Macrocycle and an Isophthalamide Head Unit

Contact Info

Product

Resources

About

VT ¹H NMR Investigations of Resonance-Assisted Intramolecular Hydrogen Bonding in 4-(Dimethylamino)-2‘-hydroxychalcone