Binding of group 15 and group 16 oxides by a concave host containing an isophthalamide unit

• Jens Eckelmann,
• Vittorio Saggiomo,
• Svenja Fischmann and
• Ulrich Lüning

Beilstein J. Org. Chem. 2012, 8, 11–17, doi:10.3762/bjoc.8.2

• halide anions. A general method for a quick estimation of the strength of binding derived from only a few data points is presented and gives an estimated Kass of pyridine-N-oxide of ca. 40 M−1, NMR titration confirms 25 M−1. Keywords: anion binding; association constant; estimation of binding constants

• constants were identified. Estimation rather than an exact determination of Kass would be fair enough. Once a good candidate is recognized, a standard determination of the association constant, for example, by NMR titration, can be done. With Δδmax unknown, the magnitude of the CIS cannot distinguish

• Supporting Information File 1, page S12), Kass for the best binder to 1, pyridine-N-oxide (PyNO), was estimated to be ca. 40 M−1. A subsequent NMR titration of host 1 with PyNO provided an association constant of 25 M−1 (see Supporting Information File 1). Remarkably, chloride ions are only very weakly bound

NMR studies of anion-induced conformational changes in diindolylureas and diindolylthioureas

• Damjan Makuc,
• Jennifer R. Hiscock,
• Mark E. Light,
• Philip A. Gale and
• Janez Plavec

Beilstein J. Org. Chem. 2011, 7, 1205–1214, doi:10.3762/bjoc.7.140

• mode for the 3·AcO− 1:1 complex. Stability constants of compound 1 measured in DMSO-d6/0.5% water, DMSO-d6/10% water and DMSO-d6/25% water and compound 2 in DMSO-d6/0.5% water at 298 K by 1H NMR titration techniques [37]. Selected 1H and 15N NMR chemical shifts for 1–4 (in ppm).a Selected NOE

A new fluorescent chemosensor for fluoride anion based on a pyrrole–isoxazole derivative

• Zhipei Yang,
• Kai Zhang,
• Fangbin Gong,
• Shayu Li,
• Jun Chen,
• Jin Shi Ma,
• Lyubov N. Sobenina,
• Albina I. Mikhaleva,
• Guoqiang Yang and
• Boris A. Trofimov

Beilstein J. Org. Chem. 2011, 7, 46–52, doi:10.3762/bjoc.7.8

• emission spectra upon the addition of F−, resulting in highly selectivity for fluoride detection over other anions, such as Cl−, Br−, I−, HSO4−, H2PO4− and AcO− in CH3CN. 1H NMR titration, time-dependent density functional theory (TDDFT) calculations and other experiments confirm that the sensing process

• recognize fluoride anion (F−) with high selectivity and sensitivity over other anions (Cl−, Br−, I−, HSO4−, H2PO4− and AcO−). Both 1H NMR titration experiments and time-dependent density functional theory (TDDFT) calculations demonstrated that the mechanism is deprotonation of the pyrrole-NH. Results and

• −. 1H NMR titration 1H NMR titration was also carried out to confirm the deprotonation of receptor 1 by F−. Figure 9 shows the series of 1H NMR spectra of 1 upon the addition of increasing amounts of TBAF in DMSO-d6. As discussed above, HF2− anion was formed when the receptor was deprotonated by F− via

Preparation, structures and preliminary host–guest studies of fluorinated syn-bis-quinoxaline molecular tweezers

• Markus Etzkorn,
• Jacob C. Timmerman,
• Matthew D. Brooker,
• Xin Yu and
• Michael Gerken

Beilstein J. Org. Chem. 2010, 6, No. 39, doi:10.3762/bjoc.6.39

• –c, depicting the inversion of the electrostatic potential in the pincer subunits upon increasing the degree of fluorination. NMR titration experiments with electron-rich arenes (1,4-dimethoxybenzene, 1,3,5-trimethoxybenzene, N,N-dimethylaniline, N,N,N′,N′-tetramethyl-p-phenylenediamine) were carried

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• ion binding processes are direct absorption and emission measurements utilizing chromophores in the receptor or analyte molecule, displacement assays with suitable dyes, NMR titration experiments, isothermal titration calorimetry and transport through an organic phase monitored by HPLC, NMR [37][38

• and (S)-1-methyl-1,2-propanediol for the enantiomeric recognition of amino acid ester derivatives [161]. The four similar macrocycles have been shown to be complexing agents for primary organic ammonium salts by 1H NMR titration. The best example, the depicted host 29, exhibited enantioselective

• showed a considerable binding affinity and enantiomeric discrimination of aromatic amine salts [162]. The binding properties were evaluated by 1H NMR titration in acetonitrile. For the (R,R)- and (S,S)-configurated host with a phenyl residue, the highest differences in the Kass values were observed: (R

(Pseudo)amide-linked oligosaccharide mimetics: molecular recognition and supramolecular properties

• José L. Jiménez Blanco,
• Fernando Ortega-Caballero,
• Carmen Ortiz Mellet and
• José M. García Fernández

Beilstein J. Org. Chem. 2010, 6, No. 20, doi:10.3762/bjoc.6.20

• phosphate were obtained from NMR titration experiments for both series of glucooligomers. The binding affinity of the thiourea and guanidine oligomers was stronger than in the case of the urea analogues. Stimulated by the interesting supramolecular properties and applications of cyclodextrins (CDs), a range

• and evaluated as phosphate binders in water (Figure 20) [76]. Association constants (Kas) for binding with dimethyl and phenyl phosphate were obtained from NMR titration experiments for both compounds. The results indicated that the binding strength depends strongly on the acidity of the NH protons

Synthesis of indolo[3,2-b]carbazole-based new colorimetric receptor for anions: A unique color change for fluoride ions

• Ajit Kumar Mahapatra,
• Giridhari Hazra and
• Prithidipa Sahoo

Beilstein J. Org. Chem. 2010, 6, No. 12, doi:10.3762/bjoc.6.12

• ), and not hydrogen bonding to it, is responsible for the drastic color change [47], as a result of a change in the optical properties of chromogenic indolocarbazole skeleton. This is in agreement with the NMR titration data. Such deprotonation was related to the acidity of the H-bond donor site and the

Size selective recognition of small esters by a negative allosteric hemicarcerand

• Holger Staats and
• Arne Lützen

Beilstein J. Org. Chem. 2010, 6, No. 10, doi:10.3762/bjoc.6.10

• esters 5–7, however, did not result in any significant shifts indicating size-selective discrimination of the different esters. In order to evaluate this phenomenon further we performed an NMR titration to determine the association constant for the binding of the arguably best guest ethyl acetate

• as the internal standard. Analysis of the binding isotherms obtained from the NMR titration experiments was done by non-linear regression methods. Qualitative binding studies of 2 and the model substrates 3–7. 1H NMR spectra (500.1 MHz, 298 K in mesitylene-d12, c0(2) = 5 mmol/L) of a) 2, b) 2 and 15

• equiv of 3, c) 2 and 15 equiv of 4, d) 2 and 15 equiv of 5, e) 2 and 15 equiv of 6, f) 2 and 15 equiv of 7. Marked in red rectangles are the regions of the signals of the acetal and some of the bipyridine hydrogen atoms of 2. 1H NMR titration (500.1 MHz, 298 K, c0(2) = 5.3 mmol/L) of 2 with increasing

Recognition properties of receptors consisting of imidazole and indole recognition units towards carbohydrates

• Monika Mazik and
• André Hartmann

Beilstein J. Org. Chem. 2010, 6, No. 9, doi:10.3762/bjoc.6.9

• carbohydrates were investigated by 1H NMR spectroscopic titrations in CDCl3 and DMSO-d6/CDCl3 mixtures. The stoichiometry of the receptor–sugar complexes was determined by mole ratio plots [51][52] and by the curve-fitting analysis of the titration data [53]. The 1H NMR titration experiments [54] with octyl β

Synthesis and binding studies of two new macrocyclic receptors for the stereoselective recognition of dipeptides

• Ana Maria Castilla,
• M. Morgan Conn and
• Pablo Ballester

Beilstein J. Org. Chem. 2010, 6, No. 5, doi:10.3762/bjoc.6.5

• themselves can be regarded as strands 1 and 3 of a three-stranded β-sheet, with cross-linking between the chains through the 4-position of adjacent phenylalanine residues. We also report on the conformational equilibria of these receptors in solution as well as on their tendency to dimerize. 1H NMR titration

• study of the molecular recognition properties of the receptors toward the different guests. All binding constants were determined using 1H NMR titration experiments. As an example, Figure 10a shows a series of spectra acquired during the titration of receptor 2 with n-C6H13-D-Ala-D-Ala-NH2. We monitored

• temperature show that the variation in chemical shift fits a simple theoretical dimerization model, although higher order aggregation cannot be ruled out. Using 1H NMR titration experiments we have determined the association constant values of the 1:1 complexes formed between receptors 1, 2, 15, and 17 and a