DMSO-d6 Solution Research Articles

Crystal structure and NMR spectroscopic characterization of 1,5-bis(2-hydroxy-3-methoxybenzylidene)carbonohydrazide

The solid-state structure of a symmetrical carbohydrazone, namely 1,5-bis(2-hydroxy-3-methoxybenzylidene)carbonohydrazide was determined by X-ray single crystal diffraction method. Compound 1 crystallizes in the monoclinic space group P21/n with unit cell parameters a= 10.1198(6), b= 22.7847(11), c= 15.1738(10) Å, β= 100.458(6)°, Z= 4, V= 3440.6(3) Å3, R1= 0.0540. Crystal structure of 1 is defined by two crystallographic independent molecules, which are bonded via N–H···O hydrogen bond. The organic molecules are as keto tautomers with respect to the carbamide fragment, and adopt the anti conformation. 1D and 2D NMR experiments have argued on the presence of the title compound in DMSO-d6 solution mostly as keto tautomer in syn conformation, and enol-imino form when considering o-vanillin residue.

Synthesis, X-Ray, Spectral Characterization, DFT, and Molecular Docking Calculations of 2-(5-Nitro-1-H-Indazol-1-yl) Acetic Acid

In this work, theoretical and experimental studies of a new Indazole derivative named 2-(5-nitro-1-H-indazol-1-yl) acetic acid (3), including the synthesis and characterization by 1H and 13C-NMR, FT-IR, UV spectroscopies are reported together with its X-ray crystal structure. The compound crystallizes in the monoclinic crystal system of P21/c space group and unit cell constants: a = 7.8541(10) Å, b = 7.9274(11) Å, c = 15.877(2) Å, β = 101.149(5)°. In the crystal, O–H···N and C–H···O hydrogen bonds form a 3-D network structure containing small channels running parallel to the b-axis. B3LYP/6-311++G** calculations in the gas phase and ethanol solution suggest the existence of C1 and C2 conformers where the structure of C1 in both media is in agreement with that observed by X-ray diffraction. Probably, the high values observed in the dipole moments of C1 justify its presence in gas and solution phases. The stabilities of both forms were justified by NBO and AIM calculations where C1 is more stable than C2. C1 shows a higher solvation energy, dipole moment, and higher hydration than C2 while the frontier orbitals suggest a higher reactivity of C1 over C2. Force fields and complete vibrational assignments were performed for the C1 conformer because it was detected in the solid phase. Scaled force constants for both forms are also reported. Calculated chemical shifts for (3) are consistent with the experimental 1H and 13C-NMR spectra in the DMSO-d6 solution. The anti-COVID activity of 3 is investigated by its molecular docking into the binding site of SARS CoV-2 3CLpro (3 C-like protease). It shows a moderate binding affinity into the binding site of 3 C-like protease with a maximum binding energy of −5.57 kcal mol−1.

Quantum Chemical Investigation of the Interaction of Thalidomide Monomeric, Dimeric, Trimeric, and Tetrameric Forms with Guanine DNA Nucleotide Basis in DMSO and Water Solution: A Thermodynamic and NMR Spectroscopy Analysis.

Thalidomide (TLD) was used worldwide as a sedative, but it was revealed to cause teratogenicity when taken during early pregnancy. It has been stated that the (R) enantiomer of TLD has therapeutic effects, while the (S) form is teratogenic. Clinical studies, however, demonstrated the therapeutic efficacy of thalidomide in several intractable diseases, so TLD and its derivatives have played an important role in the development and therapy of anticancer drugs. Therefore, it is important to know the molecular mechanism of action of the TLD, although this is still not clear. In what molecular interactions are concerned, it is known that drug molecules can interact with DNA in different ways, for example, by intercalation between base pairs. Furthermore, the ability of the TLD to interact with DNA has been confirmed experimentally. In this work, we report a theoretical investigation of the interaction of the R and S enantiomers of TLD, in its monomeric, dimeric, trimeric, and tetrameric forms, with guanine (GUA) DNA nucleotide basis in solution using density functional theory (DFT). Our initial objective was to evaluate the interaction of TLD-R/S with GUA through thermodynamic and spectroscopic study in dimethyl sulfoxide (DMSO) solvent and an aqueous solution. Comparison of the experimental 1H nuclear magnetic resonance (NMR) spectrum in DMSO-d6 solution with calculated DFT-PCM-DMSO chemical shifts revealed that TLD can undergo molecular association in solution, and interaction of its dimeric form with a DNA base ((TLD)2-GUA and (TLD)2-2GUA, for example) through H-bond formation is likely to take place. Our results strongly indicated that we must consider the plausibility of the existence of TLD associations in solution when modeling the complexation of the TLD with biological targets. This is new information that may provide further insight into our understanding of drug binding to biological targets at the molecular level.

Structural Studies of Monounsaturated and ω-3 Polyunsaturated Free Fatty Acids in Solution with the Combined Use οf NMR and DFT Calculations-Comparison with the Liquid State.

Molecular structures, in chloroform and DMSO solution, of the free fatty acids (FFAs) caproleic acid, oleic acid, α-linolenic acid, eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA) are reported with the combined use of NMR and DFT calculations. Variable temperature and concentration chemical shifts of the COOH protons, transient 1D NOE experiments and DFT calculations demonstrate the major contribution of low molecular weight aggregates of dimerized fatty acids through intermolecular hydrogen bond interactions of the carboxylic groups, with parallel and antiparallel interdigitated structures even at the low concentration of 20 mM in CDCl3. For the dimeric DHA, a structural model of an intermolecular hydrogen bond through carboxylic groups and an intermolecular hydrogen bond between the carboxylic group of one molecule and the ω-3 double bond of a second molecule is shown to play a role. In DMSO-d6 solution, NMR and DFT studies show that the carboxylic groups form strong intermolecular hydrogen bond interactions with a single discrete solvation molecule of DMSO. These solvation species form parallel and antiparallel interdigitated structures of low molecular weight, as in chloroform solution. This structural motif, therefore, is an intrinsic property of the FFAs, which is not strongly affected by the length and degree of unsaturation of the chain and the hydrogen bond ability of the solvent.

The Effect of Sample Preparation Techniques on Lignin Fourier Transform Infrared Spectroscopy.

The characterization and quantification of functional groups in technical lignins are among the chief obstacles of the utilization of this highly abundant biopolymer. Although several techniques were developed for this purpose, there is still a need for quick, cost-efficient, and reliable quantification methods for lignin. In this paper, three sampling techniques for fourier transform infrared (FTIR) spectroscopy were assessed both qualitatively and quantitatively, delineating how these affected the resultant spectra. The attenuated total reflectance (ATR) of neat powders and DMSO-d6 solutions, as well as transmission FTIR using the KBr pelleting method (0.5 wt%), were investigated and compared for eight lignin samples. The ATR of neat lignins provided a quick and easy method, but the signal-to-noise ratios in the afforded spectra were limited. The ATR of the DMSO-d6 solutions was highly concentration dependent, but at a 30 wt%, acceptable signal-to-noise ratios were obtained, allowing for the lignins to be studied in the dissolved state. The KBr pelleting method gave a significant improvement in the smoothness and resolution of the resultant spectra compared to the ATR techniques. Subsequently, the content of phenolic OH groups was calculated from each FTIR mode, and the best correlation was seen between the transmission mode using KBr pellets and the ATR of the neat samples (R2 = 0.9995). Using the titration measurements, the total OH and the phenolic OH group content of the lignin samples were determined as well. These results were then compared to the FTIR results, which revealed an under-estimation of the phenolic OH groups from the non-aqueous potentiometric titration, which was likely due to the differences in the pKa between the lignin and the calibration standard 4-hydroxybenzoic acid. Further, a clear correlation was found between the lower Mn and the increased phenolic OH group content via SEC analyses. The work outlined in this paper give complementary views on the characterization and quantification of technical lignin samples via FTIR.

A nuclear magnetic resonance-based study of the behavior of the tautomers of triclabendazole in DMSO-d6, in the presence of water

The benzimidazole antihelmintic agent triclabendazole (TCB) exhibits tautomeric polymorphism. It has been claimed that DMSO-d6 solutions prepared from the polymorphs of TCB display different NMR behavior. Therefore, a comprehensive NMR study was undertaken, in order to unveil the causes behind this unusual observation.In a first instance, 1H and 13C spectra of TCB were unequivocally assigned. Then, isothermal and variable temperature 1H NMR experiments were conducted in order to explore the relationship between the spectral changes with system variables: time, temperature and amount of water. Solutions prepared from both polymorphs experienced water-dependent spectral changes related to a tautomerization process at 298 K, and EXSY experiments confirmed the participation of H2O in the NH exchange. The tautomerization constant (KT = 1.14 ± 0.07) was determined from the signals of H4 at 298 K.On the other hand, variable temperature 1H NMR enabled estimation of coalescence temperatures (Tc) for the signals of H4, H6’ and NH, where a water-dependence was found for H4 (Tc = 298→334 K when H2O:TCB = 8:1→16:1). The exchange constants at coalescence (kc = 111.8 s−1 at 303 K, H2O:TCB = 9:1 and kc = 179.7 s−1 at 334 K, H2O:TCB = 16:1) were also determined. Thermodynamic data of the tautomerization, including free energy (ΔG‡ = 15.03 Kcal mol−1 at 300 K), enthalpy (ΔH‡ = 7.75 Kcal mol−1) and entropy (ΔS‡ = –0.0244 Kcal mol−1 K at 300 K) were obtained from the Eyring graph of linewidth-corrected exchange constant values of H4, while the activation energy (Eact = 8.48 Kcal mol−1) was obtained from an Arrhenius plot. A 1H NMR/chemometric approach demonstrated the reversibility of the temperature-driven changes in the range 298–355 K. Finally, a novel mechanism was proposed to account for the observations and dismiss the original claim, taking the presence of water in the system as the agent responsible for the detected variations.

Acrylamide derivatives: A dynamic nuclear magnetic resonance study.

Substituted acrylamides have found an extensive application in organic and medical chemistry; therefore, it is very important to get insight into their features such as electronic structure, spectral properties, and stereochemical transformations. A correct interpretation of the chemical behavior and biological activity of these heteroatomic systems is impossible without knowledge of the structure of stereodynamic forms and factors determining their relative stability. The structure and peculiarities of stereodynamic behavior of substituted acrylamides and their model compounds were studied by dynamic and multinuclear 1 H, 13 C, and 15 N nuclear magnetic resonance (NMR) spectroscopy in CDCl3 and DMSO-d6 solution. It has been established that acrylamides in solution are realized as Z- and E-isomers, with the E-rotamer being somewhat predominant. The obtained experimental values of the free activation energy of rotamers vary within 15-17 kcal/mol, depending on the stereochemical structure of the molecule. 15 N NMR spectroscopy is the most reliable and fastest method for determining the structural and stereochemical features of nitrogen-containing compounds.

Succinyl and Adipoyl Dihydrazones: A Solid-State, Solution and Antibacterial Study

A series of aryl-functionalized alkyl dihydrazones was prepared by condensation of succinyl or adipoyl dihydrazide and selected ortho-hydroxybenzaldehydes (2-hydroxybenzaldehyde, 2-hydroxy-1-naphthaldehyde, 2,3-dihydroxybenzaldehyde, and 2,4-dihydroxybenzaldehyde) in solution. The obtained products were structurally characterized in the solid state by single-crystal X-ray diffraction (SC-XRD), thermal analysis (TGA-DSC), and Fourier transform infrared (FTIR) spectroscopy and in DMSO-d6 solution by nuclear magnetic resonance (NMR) techniques. Combined FTIR and crystal structure data point to a N–NH–C=O tautomeric form of the hydrazone parts as well as the enol-imino tautomeric form of the aldehyde residues and a robust trans-syn conformation for the structurally investigated ones. While the molecules retain the same tautomeric form in the DMSO-d6 solution, they adopt several conformations, due to rotations around Car–C, C–N, and N–N bonds. The compounds show exceptional thermal stability, with a complex degradation pattern. Slight differences in thermal behavior correlate to alkyl chain length and aryl substituents. The in vitro cytotoxic activity of prepared dihydrazones was evaluated on THP-1 and HepG2 cell lines, while their antibacterial activity was tested against Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Moraxella catarrhalis bacteria. All compounds proved to be non-cytotoxic, and some exhibited moderate antibacterial activity.

Liquid Co-crystals of Dual-Active Phenothiazine-NSAID Drugs: Synthesis, Spectroscopic, and Thermal Characterization.

Four aliphatic phenothiazine cations (promazinium, promethazinium, chlorpromazinium, and triflupromazinium) were each paired with docusate anions and three different NSAID anions (ibuprofen, salicylate, and naproxen) to form fifteen glassy materials and one solid. The compounds were prepared via the metathesis reaction between the corresponding phenothiazine hydrochloride salts and sodium docusate or sodium NSAID salts and were obtained as liquid co-crystals with various degrees of ionization. The self-diffusion coefficients of several derivatives in 0.06 M DMSO-d6 solutions were determined using DOSY NMR spectroscopy. The influence of the size, shape of the compounds, and intermolecular forces has been investigated by using the four promazine and the four ibuprofen co-crystals. The ion pairs (or aggregates) were found to be maintained in six out of the seven compounds examined. All fifteen glassy compounds showed reversible glass transitions in the −25 to 10 °C range with the docusate derivatives exhibiting the highest thermal stability (Tonset values being at least 40 °C higher than those of the corresponding phenothiazine hydrochlorides).

Barrier Potential, Structure (Monomer and Dimer), Inter- and Intra-Molecular Interactions, Vibrational Analysis, Fukui Functions, MESP, NBO, UV and NMR Analysis of Pyridine-3-Carboxylic Acid Using Spectroscopic and DFT Approach

Pyridine-3-carboxylic (or nicotinic) (P3CA) acid has been recorded by using different spectroscopic tools like NMR (13C, 1H), UV–Vis, FT-IR and FT-Raman spectral analysis. The structural conformation examined by potential energy scan for the titled compound was obtained by using DFT computations through B3LYP method with 6–311++G(d,p) basis set. Using optimized monomer structure, the dimeric structures (head-to-tail and tail-to-tail) are obtained. The title compound exhibits inter-molecular as well as intra-molecular hydrogen bonding forming a supramolecular network. The geometrical parameters of both monomer and dimer are coinciding with the observed ones. Using vibrational frequencies, Infrared and Raman intensities were computed. The rms error between the experimental and scaled quantum mechanical frequencies is 9.77 cm−1 for P3CA. From the scaled quantum mechanical method, reliable vibrational assignments were made using PED. The site of chemical reactivity and selectivity of the title compound were estimated from frontier molecular orbitals and local reactivity descriptors. The reactive areas around the compound were evaluated by using MESP. The interactions of donor and acceptor are studied by NBO analysis. The 13C and 1H NMR chemical shifts of the title compound were determined using the gauge independent atomic orbital (GIAO) method in DMSO-d6 solution. By using UV–visible spectrum, the maximum absorption wavelength was obtained and compared with the TD-DFT method.

Bispidine Platform as a Tool for Studying Amide Configuration Stability.

In this work, the solution conformations of seventeen 3,7-diacyl bispidines were studied by means of NMR spectroscopy including VT NMR experiments. The acyl groups included alkyl, alkenyl, aryl, hetaryl, and ferrocene moieties. The presence of syn/anti-isomers and their ratios were estimated, and some reasons explaining experimental facts were formulated. In particular, all aliphatic and heterocyclic units in the acylic R(CO) fragments led to an increased content of the syn-form in DMSO-d6 solutions. In contrast, only the anti-form was detected in DMSO-d6 and CDCl3 in the case when R = Ph, ferrocenyl, (R)-myrtenyl. In the case of a chiral compound derived from the natural terpene myrtene, a new dynamic process was found in addition to the expected inversion around the amide N-C(O) bond. Here, rotation around the CO-C=C bond in the acylic R fragment was detected, and its energy was estimated. For this compound, ΔG for amide N-C(O) inversion was found to be equal to 15.0 ± 0.2 kcal/mol, and for the rotation around the N(CO)–C2′ bond, it was equal to 15.6 ± 0.3 kcal/mol. NMR analysis of the chiral bispidine-based bis-amide was conducted for the first time. Two X-ray structures are reported. For the first time, the unique syn-form was found in the crystal of an acyclic bispidine-based bis-amide. Quantum chemical calculations revealed the unexpected mechanism for amide bond inversion. It was found that the reaction does not proceed as direct N-C(O) bond inversion in the double-chair (CC) conformation but rather requires the conformational transformation into the chair–boat (CB) form first. The amide bond inversion in the latter requires less energy than in the CC form.

Solvation of the Boc–Val–Phe–nPr peptide characterized by VCD spectroscopy and DFT calculations

The conformational preferences of peptides are strongly determined by hydrogen bonding interactions. Intermolecular solute-solvent interactions compete with intramolecular interactions, which typically stabilize the secondary structure of the peptide. The analysis of vibrational circular dichroism (VCD) spectra can give insights into solvation-induced changes in the conformational distribution of small peptides. Here we describe the VCD spectroscopic characterization of the model peptide Boc-Val-Phe-nPr in chloroform as representative for a weakly interacting solvent and dimethyl sulfoxide (DMSO-d6) as a strongly hydrogen bonding solvent. We show that the conformational preferences of the peptide in chloroform are well-described by the computationally predicted distribution of the isolated molecule assuming only implicit solvation effects through a continuum solvation model. In order to simulate the spectra recorded in DMSO-d6, solvation was accounted for explicitly by computed microsolvated structures containing one to three solvent molecules. A good match of the computed spectra with the experimental data is obtained by this method. Comparing the conformational distributions in deuterated chloroform-d1 and DMSO-d6, structures with intramolecular hydrogen bonds such as the (δ,δ)-conformer family contribute to the conformational distribution only when there is no strong interaction with the solvent. This is in contrast to the results for the related Boc-Pro-Phe-nPr studied before, for which the intramolecular interaction was found to persist in DMSO-d6. Furthermore, we discuss the influence of hydrogen bonding to different numbers of solvent molecules on the spectral signatures and show that the structure of the peptide in DMSO-d6 is best described as a mixture of twofold-solvated (δ,β)- and threefold-solvated (β,β)-conformers.

Supramolecular self-associating amphiphiles: determination of molecular self-association properties and calculation of critical micelle concentration using a high-throughput, optical density based methodology.

Supramolecular self-associating amphiphiles are a class of amphiphilic salt, the anionic component of which is 'frustrated' in nature, meaning multiple hydrogen bonding modes can be accessed simultaneously. Here we derive critical micelle concentration values for four supramolecular self-associating amphiphiles using the standard pendant drop approach and present a new high-throughput, optical density measurement based methodology, to enable the estimation of critical micelle concentrations over multiple temperatures. In addition, we characterise the low-level hydrogen bonded self-association events in the solid state, through single crystal X-ray diffraction, and in polar organic DMSO-d6 solutions using a combination of 1H NMR techniques. Moving into aqueous ethanol solutions (EtOH/H2O or EtOH/D2O (1 : 19 v/v)), we also show these amphiphilic compounds to form higher-order self-associated species through a combination of 1H NMR, dynamic light scattering and zeta potential studies.

New preparation protocols for coumarin-thiosemicarbazone hybrids: Solid state characterization, and in silico/NMR studies of the Z/E isomerization equilibria in solution

In this work, two improved experimental protocols for the preparation of eight coumarin-thiosemicarbazone hybrids are described. The novel methodologies, based on the use of a microwave-assisted protocol (MW) or a sealed vessel conventionally heated reactor (SVR) are faster, more efficient and render higher yields (average increase in yield = 11% and 16%, respectively). For the solid state characterization, infrared spectra of the obtained compounds were analyzed with the aid of computational tools for signal assignation. In addition, a new crystal structure for the E isomer of compound 2d was obtained and a thorough analysis of the intra and intermolecular interactions was performed by Hirshfeld surface analysis. On the other hand, the hybrids were characterized in DMSO-d6 solution by 1H and 13C NMR experiments. All of them showed a set of minor signals neither ascribable to the products nor described in the literature. Variable temperature 1H NMR experiments revealed that a single interconversion equilibrium was operative in the solution, having thermodynamic parameters compatible to those predicted for a Z/E isomerization process by a DFT model. The most stable configuration (E) was further confirmed by DFT, calculating the 13C NMR chemical shifts for both configurations. The computational model shows that the E configuration is stabilized through the formation of a non-conventional C-H···O=C intramolecular H-bond between the methyl and carbonyl groups, adopting a conformation less sterically strained. These findings allow to gain insights into the E/Z isomerization equilibria displayed by thiosemicarbazones in solution, a phenomenon usually under described in literature, which seems to be promoted by a balance between weak intramolecular interactions that modulate the relative isomeric stability in solution.

Why Chemical Stability of Anion-Exchange Membranes Depends on the Hydration of the Aemfcs

Anion-exchange membrane (AEM) fuel cells (AEMFCs) can potentially revolutionize energy storage and delivery; however, their commercial development is hampered by the chemical decomposition of the anion exchange membranes during operation. As the current density in the AEMFC increases, more water is consumed at the cathode side, reducing the hydration level and, in turn, increasing the nucleophilicity of hydroxide anions and its capability to attack the quaternary ammonium (QA) groups.1–3 Several new QA salts and ionomers have been proposed to address this challenge, but while they perform well in ex-situ chemical studies, their performance is very limited in real AEMFC studies.In this study we experimentally show that water concentration in the environment of the hydroxide anion significantly impact its reactivity. In particular, we compare different QA salts that have been previously studied and test their alkaline stability at different hydration levels, as well as different temperatures. We measure the kinetics of the hydroxide-QA chemical reaction and use the data as an experimental base to understand how microsolvation affects the hydroxide reactivity – as a nucleophile, a base, and a reducing agent.4,5 The results demonstrated a disparity in the water microsolvation effect of hydroxide through E2 and SN2 kinetic experiments with two stable QA salts, trimethylbenzyl ammonium bromide (TMBA) and 6-azonia-spiro [5,5] undecane bromide (ASU) – at high hydration levels, when hydroxide first solvation shell is fully hydrated, ASU is more stable than TMBA. However, at low hydration levels, when hydroxide ion presents low microsolvation, TMBA is significantly more stable than ASU (figure 1).6 The reaction rate constants indicate that the ASU reaction kinetics, which is a consequence of hydroxide basicity, is significantly more affected by the change in microsolvation than TMBA reaction kinetics, which depends on hydroxide nucleophilicity. These results have important implications for long term operation of AEMFCs. Figure 1. TMBA and ASU concentrations as a function of time in 0.6 M OH- in DMSO-d6 solutions for hydration level λ = 1 and 8.

A straightforward synthesis of neutral hexacoordinated silicon(IV) complexes with SiN6 skeleton

Three neutral hexacoordinate silicon(IV) complexes with SiN6 skeleton were obtained via one-pot synthesis by using tetra(thiocyanato-N)silane, Si(NCS)4 with an equimolar amount of 2,2′-bipyridyl (bipy), 4,4′-dimethyl-2,2′-dipyridyl (dmp) and 1,10-phenanthroline (phen) respectively. The complexes obtained; (bipy)Si(NCS)4 (1), (dmp)Si(NCS)4 (2), and (phen)Si(NCS)4 (3) belong to a family of neutral hexacoordinate silicon(IV) with SiN6 coordinating framework, which has been less studied both by single-crystal X-ray diffraction and 29Si NMR spectroscopies. All the complexes were characterized by single-crystal X-ray diffraction, solution 1H, 13C{H}, 29Si, solid-state 29Si CP/MAS NMR spectroscopies, and elemental analysis was used to confirm the structures. Comparison of the 29Si chemical shieldings of the complexes 1–3 in the solution and solid-state indicated that all complexes maintain the hexacoordination at silicon atom in DMSO-D6 solution. This works demonstrated the synthetic potential of Si(NCS)4 for the synthesis of new neutral hexacoordinate silicon complexes with SiN6 skeleton via one-pot synthesis.

Base-Catalyzed H/D Exchange Reaction of Difluoromethylarenes.

The budding deuteriodifluoromethyl group (CF2D) is a potentially significant functional group in medicinal chemistry. Herein, we investigated t-BuOK-catalyzed H/D exchange reaction of difluoromethylarenes in DMSO-d6 solution. The method provides excellent deuterium incorporation at the difluoromethyl group. Meanwhile, the effect of a trace amount of D2O in DMSO-d6 solution on the deuteration reaction was also investigated.

A structural analysis of 2,5-diaryl-4H-2,4-dihydro-3H-1,2,4-triazol-3-ones: NMR in the solid state, X-ray crystallography, and GIPAW calculations.

The 1 H, 13 C, 15 N, and 19 F nuclear magnetic resonance (NMR) spectra of 11 2,5-diaryl-2,4-dihydro-3H-1,2,4-triazol-3-ones have been acquired in DMSO-d6 solution and the 13 C, 15 N, and 19 F NMR spectra have also been acquired in the solid state (solid-state nuclear magnetic resonance [SSNMR] and magic angle spinning [MAS]). The X-ray structures of Compounds 3, 5, and 6 have been determined by X-ray diffraction. Theoretical calculations at the gauge-independent atomic orbital (GIAO)/B3LYP/6-311++G(d,p) level have provided a set of 321 chemical shifts that were compared with 310 experimental values in DMSO-d6 . To obtain good agreements, some effects need to be included. The SSNMR chemical shifts have been compared with gauge-including projector-augmented wave (GIPAW) calculations and with the heavy atom-light atom (HALA) effects.

Synthesis of 6-Mercaptohexanoylhydrazones of Mono- and Disaccharides as a Potential Glycoligands of Noble Metal Glyconanoparticles

The 1H and 13C NMR spectroscopy was used to study the structure of previously unknown aldose series condensation products (L-fucose, L-rhamnose, D-mannose, D-galactose, D-glucose, N-acetyl-D-glucosamine, N-acetyl-D-mannosamine, D-lactose and D-maltose) with 6-mercapto­hexanoic acid hydrazide—promising glycoligands of noble metal nanoparticles. It was shown that L-fucose, L-rhamnose, D-mannose, D-galactose and N-acetyl-D-mannosamine derivatives exist in solution in DMSO-d6 as a tautomeric mixture of open hydrazone and cyclic pyranose forms. The linear hydrazone form is represented by a set of Z′,E′-conformational isomers, which differ in the arrangement of substituents relative to the C–N amide bond in comparable amounts. The condensation products obtained on the basis of D-glucose, N-acetyl-D-glucosamine, D-lactose and D-maltose in the crystalline state and in solutions in DMSO-d6 have an exclusively cyclic pyranose structure represented by α,β-configurational isomers. A similar transition to the pyranose form is observed in solutions of all the studied compounds in D2O.

Urea-Based Macrocycle Selective for Sulfate and Structurally Sensitive to Water

An unsymmetrical semi-rigid tetraurea macrocycle, 1, selectively traps SO42- with high affinity in a 0.5% water:DMSO-d6 solution (Ka = 90,500 M-1). The macrocycle displays somewhat less affinity fo...