High-resolution 13C NMR Spectroscopy Research Articles

1-(Dicyanomethylene)-3-hydroxy-1H-indene-2-carboxylic Acid

Bulk heterojunction solar cells are among the most promising organic solar cells (OSCs). One of the two important parts of OSCs are acceptors, and the development of the design and synthesis of non-fullerene acceptors involves an electron-deficient heterocyclic central core and anchor acceptor malonitrile derivatives of 3-methylene-2,3-dihydro-1H-inden-1-ones. In this communication, an intermediate for the synthesis of this compound, 1-(dicyanomethylene)-3-hydroxy-1H-indene-2-carboxylic acid, was prepared by the Perkin reaction of 2-(3-oxoisobenzofuran-1(3H)-ylidene)malononitrile with tert-butyl acetoacetate in the presence of acetic anhydride and triethylamine. The structure of the newly synthesized compound was established by means of elemental analysis, high-resolution mass spectrometry, 1H NMR, 13C NMR and IR spectroscopy, and mass spectrometry.

Understanding the Solid-State Structure of Riboflavin through a Multitechnique Approach.

Crystalline riboflavin (vitamin B2) performs an important biological role as an optically functional material in the tapetum lucidum of certain animals, notably lemurs and cats. The tapetum lucidum is a reflecting layer behind the retina, which serves to enhance photon capture and vision in low-light settings. Motivated by the aim of rationalizing its biological role, and given that the structure of biogenic solid-state riboflavin remains unknown, we have used a range of experimental and computational techniques to determine the solid-state structure of synthetic riboflavin. Our multitechnique approach included microcrystal XRD, powder XRD, three-dimensional electron diffraction (3D-ED), high-resolution solid-state 13C NMR spectroscopy, and dispersion-augmented density functional theory (DFT-D) calculations. Although an independent report of the crystal structure of riboflavin was published recently, our structural investigations reported herein provide a different interpretation of the intermolecular hydrogen-bonding arrangement in this material, supported by all the experimental and computational approaches utilized in our study. We also discuss, more generally, potential pitfalls that may arise in applying DFT-D geometry optimization as a bridging step between structure solution and Rietveld refinement in the structure determination of hydrogen-bonded materials from powder XRD data. Finally, we report experimental and computational values for the refractive index of riboflavin, with implications for its optical function.

4,4-Bis(2-ethylhexyl)-6-(9-(2-ethylhexyl)-2,3,4,4a,9,9a-hexahydro-1H-carbazol-6-yl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2-carbaldehyde

Dyes with a donor–π–spacer–acceptor (D-π-A) structure containing a dicyanovinyl group as an acceptor have recently been of interest for the production of single-component organic solar cells. The most convenient precursors for their synthesis are the corresponding aldehydes. In this communication, 4,4-bis(2-ethylhexyl)-6-(9-(2-ethylhexyl)-2,3,4,4a,9,9a-hexahydro-1H-carbazol-6-yl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2-carbaldehyde was synthesized by the Suzuki cross-coupling reaction between 4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-dicarbaldehyde and 9-(2-ethylhexyl)-6-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-2,3,4,4a,9,9a-hexahydro-1H-carbazole in the presence of tetrakis(triphenylphosphine)palladium(0). The structure of the newly synthesized compound was established by means of high-resolution mass spectrometry, 1H, 13C NMR, IR, and UV spectroscopy.

4,7-Bis(2,3,3a,8b-tetrahydrocyclopenta[b]indol-4(1H)-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine

Donor-acceptor-donor (D-A-D) type molecules are of interest as components in organic light emitting diodes (OLEDs). In this communication, 4,7-bis(2,3,3a,8b-tetrahydrocyclopenta[b]indol-4(1H)-yl)-[1,2,5]thiadiazolo[3,4-c]pyridine was obtained by two successive reactions—aromatic nucleophilic substitution SNAr and Buchwald-Hartwig cross-coupling reaction. The structure of newly synthesized compounds was established by elemental analysis, high resolution mass-spectrometry, 1H, 13C NMR, IR and UV spectroscopy and mass-spectrometry. The luminescent properties of the title compound were studied.

4-Amino-3-(1-{[amino(3-methyl-2-oxido-1,2,5-oxadiazol-4-yl)methylene]hydrazinylidene}ethyl)-1,2,5-oxadiazole 2-Oxide

Functionally substituted 1,2,5-oxadiazole 2-oxides (furoxans) are important pharmaceutical scaffolds used for the preparation of various pharmacologically active substances. Furoxans bearing hydrazone functionality are considered as promising drug candidates for the treatment of neglected diseases. However, pharmacologically oriented hydrazones derived from (furoxanyl)amidrazones and acetylfuroxans have remained unknown so far. In this communication, a simple method for the synthesis of 4-amino-3-(1-{[amino(3-methyl-2-oxido-1,2,5-oxadiazol-4-yl)methylene]hydrazinylidene}ethyl)-1,2,5-oxadiazole 2-oxide is described. The structure of the synthesized compound was established by elemental analysis, high-resolution mass spectrometry, 1H, 13C NMR and IR spectroscopy.

5,5′-(Piperazine-1,4-diyl)bis(4-chloro-3H-1,2-dithiol-3-one)

Conjugates of 3H-1,2-dithiol-3-ones with various biologically active compounds are intensively investigated. Although many derivatives of this class have been described in the literature, the compounds containing two dithiole cycles have been explored much less. In this communication, it was shown that the reaction of 4,5-dichloro-3H-1,2-dithiol-3-one with piperazine can selectively lead to the mono-product, 4-chloro-5-piperazin-1-yl-3H-1,2-dithiol-3-one and bis-product, 5,5′-(piperazine-1,4-diyl)bis(4-chloro-3H-1,2-dithiol-3-one). The structure of the synthesized compounds was established by elemental analysis, high resolution mass-spectrometry, 1H, 13C NMR and IR spectroscopy, and mass-spectrometry.

N-[3-(Chloromethyl)-1,2-benzisoxazol-5-yl]acetamide

Functionally substituted 1,2-benzisoxazoles are very important and promising heterocycles with various pharmacological activities. Benzoxazoles containing reactive 3-chloromethyl and 5-amino groups are practically unexplored derivatives in this series. In this communication, the simple method for the synthesis of N-[3-(chloromethyl)-1,2-benzisoxazol-5-yl]acetamide which is an interesting precursor for the preparation of a series of 3,5-disubstituted benzoxazoles was described. The structure of the synthesized compound was established by elemental analysis, high-resolution mass spectrometry, 1H, 13C NMR and IR spectroscopy, and mass spectrometry.

5,5′-Thiobis(4-chloro-3H-1,2-dithiole-3-thione)

3H-1,2-Dithiole-3-thiones are important compounds with many types of significant pharmacological activity. Although many derivatives of this class have been described in the literature, their thioethers have not previously been obtained. In this communication, it is shown that the reaction of 4,5-dichloro-3H-1,2-dithiole-3-thione with potassium isocyanate unexpectedly gave 5,5′-thiobis(4-chloro-3H-1,2-dithiole-3-thione). The structure of the synthesized compound was established by elemental analysis, high-resolution mass spectrometry, 13C NMR and IR spectroscopy, and mass spectrometry.

4-Bromobenzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole)

Bromoderivatives of benzofused 1,2,5-thiadiazoles are important precursors for the synthesis of dyes, which are widely used to design effective photovoltaic materials. In this study, 4-bromobenzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole was selectively obtained from the bromination of benzo[1,2-d:4,5-d′]bis([1,2,3]thiadiazole. The structure of the newly synthesized compound was established by means of elemental analysis, high-resolution mass spectrometry, 1H-, 13C-NMR, IR and UV spectroscopy and mass spectrometry.

Phosphate buffer-catalyzed kinetics of mutarotation of glucosamine investigated by NMR spectroscopy

Glucosamine (2-amino-2-deoxy-d-glucose, GlcN) is a naturally occurring amino monosaccharide that is essential for a variety of biological functions, it is mainly involved in the formation of polysaccharide structures. It was recently reported to enable the imaging of cancerous tumors as an exogenous contrast agent using the MRI technique of chemical exchange saturation transfer (CEST). In preparation for the clinical use of GlcN, its anomeric equilibrium and mutarotation rate constants were directly investigated in this study utilizing high resolution 1H and 13C NMR spectroscopy. The effects of GlcN concentration, temperature, pH and buffer on the mutarotation rate constant and mutarotation equilibrium were measured. The mutarotation rate constant increased markedly with increasing GlcN concentrations. The rate constant of mutarotation of GlcN at room temperature was 2.2 × 10−4 - 5.0 × 10−4 s−1 at concentrations of 0.02–0.5 M, corresponding to a time of 3.8–1.7 h to reach 95% equilibrium. The anomeric ratio was strongly pH-dependent. The influence of phosphate buffer on the apparent rate constant of GlcN mutarotation was investigated. For phosphate buffer saline values between 0 and 50 mM, there was a six-fold increase in rate at pH 7.0. The mutarotation rate constant rose rapidly with pH at a phosphate concentration of 50 mM: from 0.4 × 10−3 s−1 at pH 5.0 to 7.8 × 10−3 s−1 at pH 9.4, suggesting that the catalysis is due to the HPO42− and PO43− ions. These findings might help researchers design the experimental setting for employing GlcN for cancer detection using GlcN-CEST MRI.

FUNCTIONAL MATERIALS FROM WASTE PAPER. IV. COMPARATIVE STUDY OF FUNCTIONAL COMPOSITION, SUPRAMOLECULAR STRUCTURE AND MORPHOLOGY OF POWDER CELLULOSES ISOLATED FROM WASTE PAPER, PLANT CELLULOSES AND UNCONVENTIONAL RAW MATERIALS

A comparative study of the supramolecular structure, physico-chemical properties and morphology of powder celluloses (PCs) obtained from the waste paper of newsprint and cardboard, plant cellulose and unconventional raw materials was conducted using the methods of FTIR spectroscopy, high-resolution 13C NMR spectroscopy in the solid phase, wide-angle X-ray scattering and scanning electron microscopy (SEM). According to the results of FTIR and 13C NMR spectroscopy, the functional composition of PCs is similar to that of wood PCs and matches highly purified cellulose samples. The crystallographic structure of powder samples corresponds to the structure of cellulose I. The crystallinity and transverse dimensions of crystallites are 39.4% and 40.2% and 45 Å [110] and 54 Å [110] for PC from newsprint paper and cardboard, respectively. These values considerably exceed the analogous values for the initial waste paper samples. A comparative analysis of the SEM results showed a significant similarity of PCs fibers of different origin. The results of the study of the physico-chemical properties of PCs isolated from waste paper make it possible to predict their competitive application in comparison with plant PCs.

4,7-Bis(5-(9-hexyl-9H-carbazol-3-yl)thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-d]pyridazine

Donor molecules of the D-π-A-π-D type structure are often used for applications in organic photovoltaics. In this communication, bromination of 4,7-di(thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-d]pyridazine followed by Suzuki cross-coupling with carbazoleboronic acid gave 4,7-bis( 5-(9-hexyl-9H-carbazol-3-yl)thiophen-2-yl)-[1,2,5]thiadiazolo[3,4-d]pyridazine. The structure of the newly synthesized compounds was established by high resolution mass-spectrometry, 1H, 13C NMR, IR, and UV spectroscopy and mass-spectrometry. A study of the luminescent properties of the dye showed that it exhibits fluorescence in the near infrared region of the spectrum, which makes it a promising compound for use as an active emitting layer in NIR OLED as well as for other possible applications as an IR luminophore.

Synthesis of Oxadiazole-Based-Thiourea, Evaluation of Their β-Glucuronidase Inhibitory Potential, and Molecular Docking Study

Oxadiazole-based-thiourea analogs (1–18) were synthesized and evaluated for their β-glucuronidase inhibitory activity. All analogs showed extensive β-glucuronidase inhibitory potential ranging between (IC50 = 2.20 ± 0.01 µM) to (IC50 = 52.25 ± 1.20 µM) by comparing with the standard D-Saccharic acid 1,4-lactone (IC50 = 48.30 ± 1.25 µM). Among the series, analogue 7 having IC50 value (IC50 = 2.20 ± 0.01 µM)), 16 (IC50 = 4.40 ± 0.10 µM) and 4 (IC50 = 9.20 ± 0.20 µM) showed an excellent inhibitory potential greater than that of standard D-saccharic acid-1,4- lactone. Analogue 7 (IC50 = 2.20 ± 0.01 µM) of this series having flouro group at ortho-position of phenyl ring was recognized to be most active analogue due to involvement of flouro group in hydrogen bonding with the enzyme active site. In addition, all synthesized derivatives characterized by using High Resolution Mass Spectrometry (HR-MS), 13C-NMR and Nuclear Magnetic Resonance Spectroscopy (1H-NMR proton). For better understanding of binding mode of interactions of these active analogs molecular docking study was performed. Structure Activity relationship (SAR) was also discussed.

Mechanochemical synthesis of mechanical bonds in M12L8 poly-[n]-catenanes.

Using mechanochemistry by grinding TPB and ZnBr2, an amorphous poly-[n]-catenane of interlocked M12L8 nanocages is obtained in good yields (∼80%) and within 15 minutes. The mechanical bond among the icosahedral M12L8 cages in the amorphous phase has been demonstrated by single crystal XRD, powder XRD and FT-IR spectroscopy following an amorphous-to-crystalline transformation by guest uptake of the amorphous phase. High-resolution solid-state 13C NMR spectroscopy gives insights into the local structure of the amorphous catenane focusing on TPB aromatic-aromatic interactions.

7,7’-(4,4-Bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl)bis(4-bromobenzo[c][1,2,5]thiadiazole)

2,6-Bis(benzo[c][1,2,5]thiadiazol-4-yl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophenes are of interest for the synthesis of molecules which can be employed in optoelectronic devices. In this communication, 7,7’-(4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene-2,6-diyl)bis(4-bromobenzo[c][1,2,5]thiadiazole) was obtained by direct C–H cross-coupling of 4,7-dibromobenzo[c][1,2,5]thiadiazole with 4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b’]dithiophene in the presence of palladium(II)acetate and potassium pivalate. The structure of newly synthesized compound was established by means of elemental analysis, high-resolution mass spectrometry, 1H, 13C NMR, IR and UV spectroscopy.

6-(Chloromethyl)-N,1-dimethyl-1H-pyrazolo[3,4-d]pyrimidin-4-amine

Functionally 4,6-disubstituted 1H-pyrazolo[3,4-d]pyrimidines are important compounds with various pharmacological activities. 1-Substituted 4-chloro-6-(chloromethyl)-1H-pyrazolo[3,4-d]pyrimidines are practically unexplored derivatives in this series. In this paper, it was shown that the nucleophilic substitution of 4-Chloro-6-(chloromethyl)-1-methyl-1H-pyrazolo[3,4-d]pyrimidine with methylamine produced selectively 4-substituted product, 6-(chloromethyl)-N,1-dimethyl-1H-pyrazolo[3,4-d]pyrimidin-4-amine. The structure of the synthesized compound was established by elemental analysis, high resolution mass-spectrometry, 1H, 13C-NMR, and IR spectroscopy, mass-spectrometry, and X-ray analysis.

N,N-Bis(4′-(hexyloxy)-[1,1′-biphenyl]-4-yl)thiophen-2-amine

N,N-Diarylthiophen-2-amine units are of great interest for the synthesis of optoelectronic devices. In this communication, N,N-bis (4′-(hexyloxy)-[1,1′-biphenyl]-4-yl)thiophen-2-amine was obtained by means of a Buchwald–Hartwig cross-coupling reaction of bis(4′-(hexyloxy)-[1,1′-biphenyl]-4-yl)amine and 2-bromothiophene in the presence of tris(dibenzylideneacetone)dipalladium(0), tri-tert-butyl phosphine and sodium tert-butanolate. The structure of newly synthesized compounds was established by means of elemental analysis, high-resolution mass spectrometry, 1H, 13C NMR, IR and UV spectroscopy and mass-spectrometry.

Methane storage in clathrate hydrates containing water‐miscible oxirane promoters

As the share of natural gas in the global demand for energy continues to increase, there is a growing need for sustainable, energy-efficient, and cost-effective natural gas storage and transportation technologies. This study investigates methane hydrates (MHs) containing two oxirane compounds, namely, propylene oxide (PO) and epoxyisobutane (EIB), for their potential use in hydrate-based methane storage (HBMS) applications. The microstructures of the MHs containing both PO and EIB were identified as the sII type by high-resolution powder diffraction (HRPD), 13C NMR, and Raman spectroscopy. Moreover, the addition of PO/EIB significantly improved the thermodynamic stability of simple MH. In particular, as EIB increased the equilibrium temperature by 15 K, the EIB + CH4 hydrate remained stable up to ambient temperature (19°C) even under a mild pressure (30 bar). It was also clearly demonstrated that PO and EIB act as simple hydrate formers (SHFs) with good water miscibility. The EIB + CH4 hydrate also showed a remarkable CH4 capacity of 0.117 mol CH4/mol H2O or 117 m3 CH4 (at STP)/m3 hydrate, nearly identical to the theoretical maximum. It is believed that both PO and EIB could potentially be employed to facilitate sustainable and energy-efficient HBMS technologies owing to the combined excellence of their high promotion capability and energy density, and good water miscibility. Novelty statements Both PO and EIB act as powerful promoters with good water miscibility. Both PO and EIB act as simple sII hydrate formers. Approximately 120 m3 of methane gas can be stored in 1 m3 of EIB hydrate.

(2,3-Dihydro-1H-indol-5-ylmethyl)amine

New (2,3-dihydro-1H-indol-5-ylmethyl)amine was synthesized from 2-((1-acetylindolin-5-yl)methyl)isoindoline-1,3-dione by simultaneous deprotection of phthalimide and acetyl groups. The structure of the newly synthesized compounds was established by elemental analysis, high resolution mass-spectrometry, 1H, 13C NMR and IR spectroscopy and mass-spectrometry. The resulting compound is a convenient intermediate for various disubstituted 1-(indolin-5-yl)methanamines, which may be of interest as substances with useful pharmacological properties.

Tert-Butyl Bis(4′-(Hexyloxy)-[1,1′-biphenyl]-4-yl)carbamate

New donor building blocks, i.e., triarylamino derivatives, are of great interest for the production of organic photovoltaic materials. In this communication, bis(4′-(hexyloxy)-[1,1′-biphenyl]-4-yl)amine was synthesized in a two-step process via hydrolysis of its tert-butyl carbamate derivative. tert-Butyl bis(4′-(hexyloxy)-[1,1′-biphenyl]-4-yl)carbamate was obtained by Suzuki cross-coupling reaction of tert-butyl bis(4-bromophenyl)carbamate and (4-(hexyloxy)phenyl)boronic acid in the presence of tetrakis(triphenylphosphine)palladium(0). The structure of newly synthesized compounds was established by means of elemental analysis, high resolution mass-spectrometry, 1H, 13C-NMR, IR and UV spectroscopy and mass-spectrometry.