Color Compounds Removal from Tequila Vinasses Using Silica Gel Adsorbents Functionalized with Thiol Moieties: Equilibrium and Kinetics Studies.

Tequila vinasses are organic wastes generated during ethanol fermentation at elevated temperatures (≥90 °C) and pH ≤ 4.0, making them hazardous to the environment. This paper describes a new, simplified UV-vis spectroscopy-based procedure for monitoring the adsorption of color compounds in tequila vinasses onto silica-based adsorbents, along with an optimized synthesis method to produce the most efficient sol-gel synthesized thiol-functionalized adsorbent.

Keep Your TEMPO Up: Nitroxide Radicals as Sensors of Intermolecular Interactions.

This study examines experimental data on the influence of the surrounding medium and non-covalent interactions on the isotropic hyperfine coupling constant, A(N), of the stable nitroxide radical 2,2,6,6-Tetramethylpiperidin-1-yl)oxyl (TEMPO) in solution. The data were used to identify a density functional theory functional/basis set combination that accurately reproduces the experimental A(N) values. The variations in A(N) due to external factors are two orders of magnitude greater than the accuracy of its experimental measurements, making A(N) a highly sensitive experimental probe for quantifying these effects.

Monitoring structure and coordination chemistry of CoO-based oxygen evolution catalysts by nitrogen-14/-15 and cobalt-59 NMR spectroscopy.

The structural features of cobalt-based oxygen evolution catalysts are elucidated by combining high-field MAS NMR spectroscopy and DFT calculations. The superior photocatalytic activity of the heterogeneous system over its homogeneous counterpart is rationalised by the structural features. The higher activity is caused by a more favourable electron-withdrawing character of the framework.

Probing the Isolobal Relation between Cp'''NiP and White Phosphorus by Experimental Charge Density Analysis.

An in-depth analysis of the description of bonding within Cp'''Ni-cyclo-P (Cp'''=1,2,4-tri-tert-butylcyclopentadienyl, [Ni]P) employing X-ray diffraction based multipolar modeling, density functional theory (DFT) as well as an "experimental wavefunction" obtained from X-ray restrained wavefunction (XRW) fitting is presented. The results are compared to DFT calculations on white phosphorus - an isolobal analogue to [Ni]P. A complementary bonding analysis shows insights into the reactivity of [Ni]P.

The Scope of the Applicability of Non-relativistic DFT Calculations of NMR Chemical Shifts in Pyridine-Metal Complexes for Applied Applications.

Heavy metals are toxic, but it is impossible to stop using them. Considering the variety of molecular systems in which they can be present, the multicomponent nature and disorder of the structure of such systems, one of the most effective methods for studying them is NMR spectroscopy. This determines the need to calculate NMR chemical shifts for expected model systems.

Weak, Broken, but Working-Intramolecular Hydrogen Bond in 2,2'-bipyridine.

From an academic and practical point of view, it is desirable to be able to assess the possibility of the proton exchange of a given molecular system just by knowing the positions of the proton acceptor and the proton donor. This study addresses the difference between intramolecular hydrogen bonds in 2,2'-bipyridinium and 1,10-phenanthrolinium. Solid-state N NMR and model calculations show that these hydrogen bonds are weak; their energies are 25 kJ/mol and 15 kJ/mol, respectively.

Experimentally Established N NMR Absolute Shielding Scale for Theoretical Calculations.

The nitrogen atom of 2,6-di--butyl-,-diethylpyridin-4-amine (DEAP) is not available for non-covalent interactions. This molecule has been used to define the reference N NMR absolute chemical shielding (σ) required to convert between the chemical shift scale used in experiments and the absolute shielding scale used in theoretical calculations. The accuracy of the obtained σ was tested for solid samples of acetanilide-N, the protonated homodimer of pyridine-N, and poly(4-vinylpyridine-N).

Synthesis of a carborane-substituted bis(phosphanido) cobaltate(i), ligand substitution, and unusual P fragmentation.

Oxidative addition of the P-P single bond of an -carborane-derived 1,2-diphosphetane (1,2-C(PMes)BH) (Mes = 2,4,6-MeCH) to cobalt(-i) and nickel(0) sources affords the first heteroleptic complexes of a carborane-bridged bis(phosphanido) ligand. The complexes also incorporate labile ligands suitable for further functionalisation. Thus, the cobalt(i) complex [K([18]crown-6)][Co{1,2-(PMes)CBH}(cod)] (cod = 1,5-cyclooctadiene) bearing a labile cyclooctadiene ligand undergoes facile ligand exchange reactions with isonitriles and -butyl phosphaalkyne with retention of the bis(phosphanido) ligand.

Modeling of the Response of Hydrogen Bond Properties on an External Electric Field: Geometry, NMR Chemical Shift, Spin-Spin Scalar Coupling.

The response of the geometric and NMR properties of molecular systems to an external electric field has been studied theoretically in a wide field range. It has been shown that this adduct under field approach can be used to model the geometric and spectral changes experienced by molecular systems in polar media if the system in question has one and only one bond, the polarizability of which significantly exceeds the polarizability of other bonds. If this requirement is met, then it becomes possible to model even extreme cases, for example, proton dissociation in hydrogen halides.

1,3,5-Triaza-7-Phosphaadamantane (PTA) as a P NMR Probe for Organometallic Transition Metal Complexes in Solution.

Due to the rigid structure of 1,3,5-triaza-7-phosphaadamantane (PTA), its P chemical shift solely depends on non-covalent interactions in which the molecule is involved. The maximum range of change caused by the most common of these, hydrogen bonding, is only 6 ppm, because the active site is one of the PTA nitrogen atoms. In contrast, when the PTA phosphorus atom is coordinated to a metal, the range of change exceeds 100 ppm.

Modeling of Solute-Solvent Interactions Using an External Electric Field-From Tautomeric Equilibrium in Nonpolar Solvents to the Dissociation of Alkali Metal Halides.

An implicit account of the solvent effect can be carried out using traditional static quantum chemistry calculations by applying an external electric field to the studied molecular system. This approach allows one to distinguish between the effects of the macroscopic reaction field of the solvent and specific solute-solvent interactions. In this study, we report on the dependence of the simulation results on the use of the polarizable continuum approximation and on the importance of the solvent effect in nonpolar solvents.

Editorial to the Special Issue "Gulliver in the Country of Lilliput: An Interplay of Noncovalent Interactions".

Noncovalent interactions allow our world to exist [...

Electric field effect on P NMR magnetic shielding.

Magnetic shielding depends on molecular structure and noncovalent interactions. This study shows that it is also measurably dependent on the electric field generated by surrounding molecules. This effect has been observed explicitly for P nucleus using the adduct under field approach.

NMR Study of Intercalates and Grafted Organic Derivatives of HLaTiO.

The protonated perovskite-like titanate HLaTiO has been used to produce organic-inorganic hybrids with simple organic molecules: methylamine, methanol, monoethanolamine, and -butylamine. The optimal pathways for the preparation of such hybrids are summarized. Solid-state NMR, combined with thermal analysis, Raman, and IR spectroscopy, has been applied to determine the bonding type in the obtained organic-inorganic hybrids.

Complexation behaviour of LiCl and LiPF- model studies in the solid-state and in solution using a bidentate picolyl-based ligand.

Structural knowledge on ubiquitous lithium salts in solution and in the crystalline state is of paramount importance for our understanding of many chemical reactions and of the electrolyte behaviour in lithium ion batteries. A bulky bidentate Si-based ligand (6) was used to create simplified model systems suitable for correlating structures of LiCl and LiPF complexes in the solid-state and in solution by combining various experimental, spectroscopic, and computational methods. Solution studies were performed using H DOSY, multinuclear variable temperature NMR spectroscopy, and quantum chemical calculations.

Inter- vs. Intramolecular Hydrogen Bond Patterns and Proton Dynamics in Nitrophthalic Acid Associates.

Noncovalent interactions are among the main tools of molecular engineering. Rational molecular design requires knowledge about a result of interplay between given structural moieties within a given phase state. We herein report a study of intra- and intermolecular interactions of 3-nitrophthalic and 4-nitrophthalic acids in the gas, liquid, and solid phases.

For Whom a Puddle Is the Sea? Adsorption of Organic Guests on Hydrated MCM-41 Silica.

Thermal and hydration effects on the mobility of compact and branched organic molecules and a bulky pharmaceutical substance loaded in submonolayer amounts onto mesoporous silica have been elucidated using H and P solid-state NMR. In all cases, the ambient hydration has a stronger effect than an increase in temperature to 370 K for water-free silica. The effect of hydration depends on the guest and ranges from complete solvation to a silica-water-guest sandwich structure to a silica-guest/silica-water pattern.

Adduct under Field-A Qualitative Approach to Account for Solvent Effect on Hydrogen Bonding.

The location of a mobile proton in acid-base complexes in aprotic solvents can be predicted using a simplified Adduct under Field (AuF) approach, where solute-solvent effects on the geometry of hydrogen bond are simulated using a fictitious external electric field. The parameters of the field have been estimated using experimental data on acid-base complexes in CDF/CDClF. With some limitations, they can be applied to the chemically similar CHCl and CHCl.

The Partner Does Matter: The Structure of Heteroaggregates of Acridine Orange in Water.

Self-assembly of organic molecules in aqueous solutions is governed by a delicate entropy/enthalpy balance. Even small changes in their intermolecular interactions can cause critical changes in the structure of the aggregates and their spectral properties. The experimental results reported here demonstrate that protonated cations of acridine orange, acridine, and acridin-9-amine form stable J-heteroaggregates when in water.

Compensation of London Dispersion in the Gas Phase and in Aprotic Solvents.

The importance of London dispersion for structure and stability of molecules with less than about 200 atoms has been established in recent years but the quantitative understanding is still largely based on computations because of a persistent lack of suitable experimental data. We herein report a comprehensive computational and experimental study of the compensation of London dispersion in proton-bound dimer dissociations showing that total compensation is largely invariant in both polar and nonpolar aprotic solvents spanning a wide range of bulk polarizabilities. Additionally, we find that compensation by solvent (which is about 40-80 %) largely dominates over compensation in the gas phase (which is about 0-40 %) for typical experimental temperatures.

Solvent effects on acid-base complexes. What is more important: A macroscopic reaction field or solute-solvent interactions?

Can the geometry of an acid-base complex in solution be reproduced in calculations using an implicit accounting for the solvent effect in the form of a macroscopic reaction field? The answer is, "Yes, it can." Is this field equal to the real electric field experienced by the complex in solution? The answer is, "No, it is not." How can the geometry be correct under wrong conditions? This question is answered using density functional theory modeling of geometric and NMR parameters of pyridine⋯HF⋯(HCF) adducts in the absence and presence of an external electric field.

Amine-Borane Dehydrogenation and Transfer Hydrogenation Catalyzed by α-Diimine Cobaltates.

Anionic α-diimine cobalt complexes, such as [K(thf) {( BIAN)Co(η -cod)}] (1; Dipp=2,6-diisopropylphenyl, cod=1,5-cyclooctadiene), catalyze the dehydrogenation of several amine-boranes. Based on the excellent catalytic properties, an especially effective transfer hydrogenation protocol for challenging olefins, imines, and N-heteroarenes was developed. NH BH was used as a dihydrogen surrogate, which transferred up to two equivalents of H per NH BH .

Simplified calculation approaches designed to reproduce the geometry of hydrogen bonds in molecular complexes in aprotic solvents.

The impact of the environment onto the geometry of hydrogen bonds can be critically important for the properties of the questioned molecular system. The paper reports on the design of calculation approaches capable to simulate the effect of aprotic polar solvents on the geometric and NMR parameters of intermolecular hydrogen bonds. A hydrogen fluoride and pyridine complex has been used as the main model system because the experimental estimates of these parameters are available for it.

NMR Study of Solvation Effect on the Geometry of Proton-Bound Homodimers of Increasing Size.

Hydrogen bond geometries in the proton-bound homodimers of quinoline and acridine derivatives in an aprotic polar solution have been experimentally studied using H NMR at 120 K. The reported results show that an increase of the dielectric permittivity of the medium results in contraction of the N···N distance. The degree of contraction depends on the homodimer's size and its substituent-specific solvation features.