Spectral Characteristics Related to Chemical Substructures and Structures Indicative of Organic Precursors from Fulvic Acids in Sediments by NMR and HPLC-ESI-MS.

The aim of this work was to determine Fulvic Acids (FAs) in sediments to better know their composition at the molecular level and to propose substructures and structures of organic precursors. The sediment samples were obtained from a priority area for the conservation of ecosystems and biodiversity in Mexico. FAs were extracted and purified using modifications to the International Humic Substances Society method.

Supramolecular arrangement and photophysical properties of a dinuclear cyanophenylboronic acid ester.

Boronic esters are useful building blocks for crystal engineering and the generation of supramolecular architectures, including macrocycles, cages and polymers (one-, two- and three-dimensional), with potential utility in diverse fields such as separation, storage and luminescent materials. The novel dinuclear cyanophenylboronic ester described herein, namely 4,4'-(2,4,8,10-tetraoxa-3,9-diboraspiro[5.5]undecane-3,9-diyl)dibenzonitrile, CHBNO, was prepared by condensation of 4-cyanophenylboronic acid and pentaerythritol and fully characterized by elemental analysis, IR and NMR (H and B) spectroscopy, single-crystal X-ray diffraction analysis and TG-DSC (thermogravimetry-differential scanning calorimetry) studies.

2,6-Dihy-droxy-4-oxo-2-(pyridin-1-ium-3-yl)-4H-1,3,2-benzodioxaborinin-2-ide 0.67-hydrate.

The asymmetric unit of the title compound, C12H10BNO5·0.67H2O, contains three independent pyridinylboronic acid esters adopting zwitterionic forms and two water mol-ecules. The six-membered heterocyclic rings in the boronic esters have half-chair conformations and the deviations of the B atoms from the boronate mean planes range from 0.

Substituent effects and pH profiles for stability constants of arylboronic acid diol esters.

Stability constants of boronic acid diol esters in aqueous solution have been determined potentiometrically for a series of meta-, para-substituted phenylboronic acids and diols of variable acidity. The constants β(11-1) for reactions between neutral forms of reactants producing the anionic ester plus proton follow the Hammett equation with ρ depending on pKa of diol and varying from 2.0 for glucose to 1.

4-[(E)-2-(Pyridin-2-yl)ethen-yl]pyridine-terephthalic acid (2/1).

The title 2:1 co-crystal, 2C12H10N2·C8H6O4, crystallizes with one mol-ecule of 4-[(E)-2-(pyridin-2-yl)ethen-yl]pyridine (A) and one half-mol-ecule of terephthalic acid (B) in the asymmetric unit. In the crystal, the components are linked through heterodimeric COOH⋯Npyridine synthons, forming linear aggregates of composition -A-B-A-B-. Further linkage through weak C-H⋯O and C-H⋯π inter-actions gives two-dimensional hydrogen-bonded undulating sheets propagating in the [100] and [010] directions.

Solvent-solvent and solvent-solute interactions in a 3D chloroform clathrate with diorganotin macrocycles in the nano-sized pores.

A 3D clathrate of deuterochloroform molecules was formed in the presence of nano-sized macrocyclic molecules.

Relative acidities and structure analysis of cis and trans isomers of 1,5-oxazaspiro[5.5] undecane derivatives by multinuclear magnetic resonance.

The relative acidities of the cis and trans isomers of a series of 1,5-oxazaspiro[5.5]undecane derivatives were determined by measuring DeltapK in acid-base titrations followed by (1)H NMR. Relative structural stabilities were determined by measuring substituent chemical shift and gamma-gauche effects in (13)C, (15)N, and (17)O NMR.

Macrocyclic diorganotin complexes of gamma-amino acid dithiocarbamates as hosts for ion-pair recognition.

The dimethyl-, di-n-butyl-, and diphenyltin(IV) dithiocarbamate (dtc) complexes [{R2Sn(L-dtc)}x] 1-7 (1, L = L1, R = Me; 2, L = L1, R = n-Bu; 3, L = L2, R = Me, x = infinity; 4, L = L2, R = n-Bu; 5, L = L3, R = Me, x = 2; 6, L = L3, R = n-Bu, x = 2; 7, L = L3, R = Ph, x = 2) have been prepared from a series of secondary amino acid (AA) homologues as starting materials: N-benzylglycine (alpha-AA derivative = L1), N-benzyl-3-aminopropionic acid (beta-AA derivative = L2), and N-benzyl-4-aminobutyric acid (gamma-AA derivative = L3). The resulting compounds have been characterized by elemental analysis, mass spectrometry, IR and NMR ((1)H, (13)C, and (119)Sn) spectroscopy, thermogravimetric analysis, and X-ray crystallography, showing that in all complexes both functional groups of the heteroleptic ligands are coordinated to the tin atoms. By X-ray diffraction analysis, it could be shown that [{Me2Sn(L2-dtc)}x] (3) is polymeric in the solid state, while the complexes derived from L3 (5-7) have dinuclear 18-membered macrocyclic structures of the composition [{R2Sn(L3-dtc)}2].

Theoretical study of the experimental coordination behavior of N-(2-aminophenyl)-D-glycero-D-gulo-heptonamide to Hg(II) ion.

The reactivity of N-(2-aminophenyl)-d-glycero-d-gulo-heptonamide (adgha), with the group 12 cations, Zn(II), Cd(II), and Hg(II), was studied in DMSO-d(6) solution. The studied system showed a selective coordination to Hg(II), and the products formed were characterized by (1)H and (13)C NMR in DMSO-d(6) solution and fast atom bombardment (FAB(+)) mass spectra. The expected coordination compounds, [Hg(adgha)](NO(3))(2) and [Hg(adgha)(2)](NO(3))(2), were observed as unstable intermediates that decompose to bis-[2-(d-glycero-d-gulo-hexahydroxyhexyl)-benzimidazole-κN]mercury(II) dinitrate, [Hg(ghbz)(2)](NO(3))(2).

Assignment of the relative configuration of spiro[4.5]decanes by 13C, 15N and 17O NMR.

The relative configuration of 11 1,4-diazaspiro[4.5]decanes (1a-1j and 1m), 15 1,4-oxazaspiro[4.5]decanes (2a-2o) and 10 1,4-dioxaspiro[4.