1H NMR Signals Research Articles

A Genetically Engineered Reporter System Designed for 2H-MRI Allows Quantitative In Vivo Mapping of Transgene Expression.

The ability to obtain quantitative spatial information on subcellular processes of deep tissues in vivo has been a long-standing challenge for molecular magnetic resonance imaging (MRI) approaches. This challenge remains even more so for quantifying readouts of genetically engineered MRI reporters. Here, we set to overcome this challenge with a molecular system designed to obtain quantitative 2H-MRI maps of a gene reporter. To this end, we synthesized deuterated thymidine, d3-thy, with three magnetically equivalent deuterons at its methyl group (-CD3), showing a singlet peak with a characteristic 2H-NMR frequency (δ = 1.7 ppm). The upfield 3.0 ppm offset from the chemical shift of the HDO signal (δ = 4.7 ppm) allows for spectrally resolving the two 2H NMR signals and quantifying the concentration of d3-thy based on the known concentration of a tissue's HDO. Following systemic administration of d3-thy, its accumulation as d3-thy monophosphate in cells expressing the human thymidine kinase 1 (hTK1) transgene was mapped with 2H-MRI. The data obtained in vivo show the ability to use the d3-thy/hTK1 pair as a reporter probe/reporter gene system to quantitatively map transgene expression with MRI. Relying on a structurally unmodified reporter probe (d3-thy) to image the expression of unmutated human protein (hTK1) shows the potential of molecular imaging with 2H-MRI to monitor gene reporters and other relevant biological targets.

Absolute Quantification of Phenylbutanoids in Zingiber cassumunar Roxb. Rhizome by Quantitative 1H NMR.

Quantitative determination of pharmacologically active constituents in medicinal plants is critical for quality control. Due to the chemical complexity of the crude plant extracts, the presence of interfering compounds is often problematic for the unambiguous quantitation of the designed bioactive compounds. Considering the method of quantification, quantitative NMR spectroscopy (qNMR) has gained substantial popularity as a powerful and effective technique for both qualitative and quantitative analyses of natural products. The aim of this study is to develop a quantitative NMR method for quantifying the bioactive phenylbutanoids in Zingiber cassumunar rhizome crude extract. Quantitative 1H NMR (qHNMR) measurements were performed on a 600 MHz NMR spectrometer using an internal standard for the determination of the absolute quantities of four phenylbutanoids in Z. cassumunar rhizome crude extract. The direct quantification of four characteristic phenylbutanoids, i.e., (E)-1-(3',4'-dimethoxyphenyl)butadiene (DMPBD), (E)-1-(2',4',5'-trimethoxyphenyl)butadiene (TMPBD), (E)-4-(3',4'-dimethoxyphenyl)but-3-en-1-ol, and (E)-4-(3',4'-dimethoxyphenyl)but-3-en-1-yl acetate, in crude extract by qHNMR using an internal standard was achieved, with high specificity and sensitivity. The selected 1H NMR signals could unambiguously be assigned and did not overlap with other resonances, including the highly similar compounds DMPBD and TMPBD. The method is linear in the concentration range of 0.70-14.52 mg/mL, with a limit of quantification of 0.46-0.68 mg/mL. The RSD values of intraday and interday precisions are in the range of 0.23%-0.74% and 0.29%-0.52%, respectively. The average recoveries are 99.54%-100.18%. A rapid, accurate, and precise method using 1H NMR for the simultaneous quantitation of four phenylbutanoids in the crude extract of Z. cassumunar rhizome was developed and validated.

Quantitative estimation and validation of Alectinib hydrochloride drug substance using quantitative nuclear magnetic resonance spectroscopy

Nuclear magnetic resonance spectroscopy has been recently used for quantitative estimation of drug substance which has numerous merits in pharmaceutical applications when compared to traditional methods of chromatography. Present study focuses on method development and validation of quantitative proton nuclear magnetic spectroscopy method for estimation of alectinib hydrochloride drug substance. This method involves use of internal standard in presence of alectinib hydrochloride. For quantitation, 1H NMR signals at 8.4 ppm and 6.7 ppm corresponding to analyte proton of alectinib and ethyl 4-(dimethyl amino) benzoate internal standard respectively were used. Moreover, this method was validated as per ICH guidelines for accuracy, precision, linearity, limit of detection, limit of quantitation, range and robustness. Assay estimation by Q-NMR is facile and time-efficient which does not require reference standard of analyte and yet accurate and precise alternative as compared to estimation by other chromatographic techniques.

Spectrochemical Insights into Aromatic Hydrocarbons in 1,2-Disubstituted Naphthalenes: Investigations Using 1D and 2D NMR Spectroscopy and X-Ray Crystallography Analysis

Naphthalene and its derivatives are often determined as markers of environmental pollution, although they are also recognized as crucial building blocks in many beneficial compounds. In the course of this study, a range of 1,2-disubstituted naphthalenes bearing nitro, amine, sulfonate, chlorine, and hydroxyl substituents were synthesized and characterized using several spectroscopic techniques, including FT-IR,1H NMR,13C NMR, DEPT-90, DEPT-135, DEPTq, elemental analysis, and high-resolution mass (HRMs). The NMR analysis of the aromatic hydrocarbon moiety in these compounds emphasized the impact of substituent variations on the appearance of 1H and 13C NMR signals. To resolve the issue of overlapping one-dimensional (1D) 1H NMR signals and determine the connectivity of hydrogen and carbon atoms from the aromatic naphtayl ring, we employed a “two-dimensional” experiment, using homonuclear correlation spectroscopy (2D 1H-1H COSY) and heteronuclear single quantum correlation (2D 1H - 13C HSQC) and heteronuclear multiple‐bond correlation spectroscopy (2D 1H - 13C HMBC). This work also investigated the correlation between 1H NMR signals and thin-layer chromatography (TLC) data. X-ray crystallography data validates that the presence of a specific group, not aligned coplanarly with the naphthyl ring, exerts a spatial influence on the manifestation of 1H NMR signals, alongside other electronic effects. This study will offer NMR data, providing insights into the potential applications and analyses of naphthalene derivatives across various theoretical and practical domains.

Three-Component Synthesis of 1-Substituted 5-Aminotetrazoles Promoted by Bismuth Nitrate.

A nontoxic bismuth-promoted multicomponent synthesis of 5-aminotetrazoles and bistetrazoles is reported. The reaction of phenyl isothiocyanate, NaN3, and amine (primary aliphatic, aromatic, and aliphatic diamine) promoted by Bi(NO3)3·5H2O under microwave heating affords good yields, short reaction times, simple workup, and purification without column chromatography. A set of diagnostic 1H NMR signals was identified as a guide for quickly elucidating the exclusive (or main) regioisomer formed, with the stronger electron donor group located at heterocyclic nitrogen 1. This regioselectivity is strongly dependent on the electronic density of the amine. It is opposite to that obtained by several thiourea desulfurization methods promoted by thiophilic metals and metal-free protocols.

Development and Validation of 1H Nuclear Magnetic Resonance Quantitative Method for Efavirenz API Quality Control

Background: The pharmaceutical industry is constantly looking for a better way to ensure and improve its products' safety, quality, and effectiveness. Since there are many attributes of the drug substance and excipients that could potentially affect the Critical Quality Attributes (CQAs) of the intermediates and the final product, the evaluation of the raw material's physicochemical characteristics is crucial as they directly affect the quality, safety, efficacy, and lot-to-lot consistency. Scientists rely on methods, like HPLC, HPTLC, LC-MS, GC-MS, and NMR, to analyze these substances. The advantage of NMR is that it is considered a primary analytical method compared to other analytical techniques. Objective: This work aimed to present a simple, rapid, specific, and accurate method by proton Nuclear Magnetic Resonance spectroscopy (1H-NMR) developed to determine the activity of the antiretroviral Efavirenz’s (EFZ) Active Pharmaceutical Ingredient (API). The method was based on quantitative NMR spectroscopy (qNMR). Methods: A Bruker Avance spectrometer (11.7 Tesla, 500 MHz for 1H) with a 5mm probe was used. The 1H-NMR signal at 7.54 ppm corresponding to the analyte of interest was employed to quantify the drug. The method was validated for specificity, selectivity, intermediate precision, linearity, range of work, accuracy, and robustness. Results: The method developed was specific and linear (r2 = 0.9998) with a value between 4.30 mg/mL and 12.40 mg/mL. The relative standard deviation for accuracy and precision was 0.4% or less. The method's robustness was demonstrated by changing four different parameters, and the difference among each was 1.2% or less. The results of this work have been found to be in agreement with those obtained from High-performance Liquid Chromatography (HPLC) analysis. Conclusion: The proposed method has been found to be a valuable and practical tool for quality control. Its applicability to determining many APIs and saving solvent use and time is highlighted.

A difunctional NMR&CD probe for specific detection and enantiomeric recognition of biothiols in complex mixtures

BackgroundBiothiols are important for numerous cellular processes, such as resisting oxidative stress and protecting cell health. Their abnormal levels and molecular configurations have been associated with various diseases. So, establishing an effective and reliable method for the specific detection and enantiomeric discrimination of diverse biothiols is highly meaningful. ResultsWe have developed a new NMR and CD probe using 1,4-dinitroimidazole, specifically targeting the thiol group. This probe allows for the specific detection and enantiomeric recognition of biothiols in complex mixtures. We achieved this by identifying the distinguishable 1H NMR signals of 2nd in imidazole-ring of the resulting 4NI-biothiols in the downfield region at 7–8 ppm and newly discovered induced CD signals within 290-430 nm. Using this probe, the limits of detection of Cys, GSH, and Hcy, the recovery rates, and the concentration of GSH extracted from HEK293T cells were determined by measuring the unique downfield 1H NMR signals. Moreover, Cys, GSH, and Hcy can be discriminated simultaneously in complicated samples at a pH range of 2–3.5. Furthermore, this probe can also be utilized to sense chiral thiol-drugs. SignificanceThis method offers a cost-effective and accurate sensing solution for the specific detection of biothiols in complex mixtures, with stereochemical recognition.

Identification and characterization of phytochemicals in methanolic extract of roots of Datura fastuosa using various techniques

BackgroundPlant extracts have attracted significant interest among researchers due to their potential bioactivity and crucial contribution to the production of pharmaceutical compounds. In this study, the primary objective was to extract, analyze and characterize the bioactive compounds found in the methanol root extract of Datura fastuosa (D. fastuosa). This was achieved using various analytical techniques such as gas chromatography/mass spectrometry (GC–MS), ultra-violet visible spectrophotometry, Fourier-transform infrared (FT-IR), nuclear magnetic radiation spectrometry (NMR) and DPPH free radical scavenging activity assay.ResultsGC–MS analysis of the methanol root crude extract identified 49 compounds. Three compounds were isolated via column chromatography; one was pure, with a sharp melting point and clean IR spectrum, while the other two showed broad melting points and IR interferences. Comprehensive investigation of the pure extract revealed a UV profile with two distinct bands (300–800 nm) and confirmed functional groups (alcohol, alkanes, alkenes, carbonyl, methylene, and methyl) through FT-IR analysis. The 1HNMR (proton nuclear magnetic resonance spectroscopy) signal confirmed the presence of forty-nine non-equivalent protons, 13CNMR (Carbon-13 nuclear magnetic resonance spectroscopy) signal confirmed the presence of 32 non-equivalent carbons and DEPT-135 (distortionless enhancement by polarization transfer-135) signal confirmed the presence of 24 carbons (17 for odd and 7 for even) which are protons containing carbons in the compound. Combining the above mentioned analyses with data obtained from the GC/MS analysis of National Institute of Standards and Technology (NIST) library, the isolated pure compound exhibited a structural similarity to 1-(7-(3-hydroxyphenyl)-1,1,4a,5,6,9,10a,10b-octamethyl-1,2,3,4,4a,4b,6a,7,8,9,10,10a,10b,11,12,12a-hexadecahydrochrysen-2-yl)propan-1-one, with a chemical formula of C35H50O2.ConclusionsThe presence of various notable compounds, including phenolics, flavonoids, alkaloids, steroids etc., within the methanol root extract of D. fastuosa signifies its pharmacological potential. The methanol crude extract demonstrated antioxidant potential compared to standard ascorbic acid, exhibiting DPPH scavenging activity. Previous research has demonstrated the bioactivity of some of these compounds, further elucidating the plant’s medicinal properties. These findings not only suggest opportunities for developing synthetic drugs but also underscore its direct therapeutic potential in addressing diverse ailments.

5,18‐Dimesitylorangarin: a Stable Antiaromatic [20]Pentaphyrin(1.0.1.0.0) Displaying Remarkable Oxidative Self‐Coupling Reactions

Abstract5,18‐Dimesitylorangarin and its BF2 complex were synthesized by double SNAr reaction of 3,5‐dibromo‐BODIPY with 2‐pyrrolydipyrrin as the first examples of meso‐aryl‐substituted orangarin. These orangarins, delineated as [20]pentaphyrin(1.0.1.0.0), are strongly antiaromatic but rather stable. The free base orangarin was coupled by oxidation with MnO2 to give a 11,11′‐linked dimer, a cyclooctatetraene(COT)‐centered trimer, and a spiro‐trimer. Fused COT‐centered 3H‐orangarin dimer was oxidized to the corresponding 2H‐orangarin dimer, which was further coupled to give a triply COT‐centered 2H‐orangarin tetramer. 3H‐Orangarin oligomers are all antiaromatic as evinced by extremely low‐field‐shifted 1H NMR signals of the inner NH and ill‐defined absorption spectra with broad tails. In contrast, COT‐centered 2H‐orangarin dimer and tetramer show moderately low‐field‐shifted NH signals and intense NIR absorbance over 900 nm, suggesting effective π‐conjugation through the COT bridge and almost non‐antiaromatic character. These orangarin oligomers exhibit many reversible redox potentials owing to the intramolecular electronic interactions. Regardless of the different aromatic characters, all the orangarin monomers and oligomers exhibit very rapid excited‐state decays.

5,18-Dimesitylorangarin: a Stable Antiaromatic [20]Pentaphyrin(1.0.1.0.0) Displaying Remarkable Oxidative Self-Coupling Reactions.

5,18-Dimesitylorangarin and its BF2 complex were synthesized by double SNAr reaction of 3,5-dibromo-BODIPY with 2-pyrrolydipyrrin as the first examples of meso-aryl-substituted orangarin. These orangarins, delineated as [20]pentaphyrin(1.0.1.0.0), are strongly antiaromatic but rather stable. The free base orangarin was coupled by oxidation with MnO2 to give a 11,11'-linked dimer, a cyclooctatetraene(COT)-centered trimer, and a spiro-trimer. Fused COT-centered 3H-orangarin dimer was oxidized to the corresponding 2H-orangarin dimer, which was further coupled to give a triply COT-centered 2H-orangarin tetramer. 3H-Orangarin oligomers are all antiaromatic as evinced by extremely low-field-shifted 1H NMR signals of the inner NH and ill-defined absorption spectra with broad tails. In contrast, COT-centered 2H-orangarin dimer and tetramer show moderately low-field-shifted NH signals and intense NIR absorbance over 900 nm, suggesting effective π-conjugation through the COT bridge and almost non-antiaromatic character. These orangarin oligomers exhibit many reversible redox potentials owing to the intramolecular electronic interactions. Regardless of the different aromatic characters, all the orangarin monomers and oligomers exhibit very rapid excited-state decays.

Self-assembly via hydrogen bonding of bis(18-crown-6)-1,3-distyrylbenzene and [2 + 2] photocycloaddition: Stereoselective synthesis of [2.2]metacyclophanes and butterfly-type thermal isomerization

The photochemistry of bis(18-crown-6)-containing 1,3-distyrylbenzene and its 2 : 2 bis-pseudo-sandwich complex with ethane-1,2-diammonium was studied. The UV irradiation of the supramolecular complex resulted in the formation of three geometric isomers of tetracrown-containing dicyclobutano[2.2]metacyclopane, differing in the orientation of the cyclobutane moieties, with the unsymmetrical isomer (>50 %) predominating. The diammonium cations used as the template could be removed after photolysis by simple extraction, and the product was obtained in high yield (82 %). The 1H NMR signals of a mixture of geometric isomers of [2.2]metacyclophane derivative were assigned resorting to quantum chemistry methods (DFT). The kinetic and thermodynamic parameters of thermal isomerization between the endo,endo- and exo,exo-isomers were measured. Tetracrown-containing dicyclobutano[2.2]metacyclophanes are homotetratopic ligands that contain four binding sites for metal and ammonium cations, which is of interest for the design of photo- and thermo-switchable supramolecular devices with a variable complex formation behavior and supramolecular machines owing to the butterfly-type thermal isomerization.

On the supramolecular interactions into a pH- and Metal-Actuated Molecular Shuttle: some insights from QTAIM modeling.

Supramolecular contacts responsible for chemical interaction of cucurbit[7]uril (CB[7]) macrocycle on a Tolyl-Viologen-Phenylene-Imidazole (T-VPI) molecular thread, at acid pH (T-VPI-H+) or after Ag+ cation addition (T-VPI-Ag+), are analytically addressed in a computational framework combining Quantum Theory of Atoms in Molecules (QTAIM) with Density Functional Theory (DFT). In this respect, the crystallographic structure (CCDC number 2217466) is taken as reference condition for addressing the nature of the chemical interactions driving the shuttling of the CB[7] between T and P stations recently observed in dilute water solutions. Beside the host(CB[7]) vs guest(T-VPI-H+ or T-VPI-Ag+) complexation, the coordination sphere of the Ag+ cation is also investigated by means of local electronic energy density - H(r) - descriptors. The derived non-covalent interaction patterns are found to support diagnostic 1H NMR signals used for detecting the mutual position of the CB[7] along the axle. This work highlights the potentialities of a QTAIM based approach in the characterization of supramolecular and metal-complexation effects in molecular aggregates such as not-interlocked synthetic molecular shuttles.

Quantifying the water saturation degree of cement-based materials by hydrogen nuclear magnetic resonance (1H NMR)

This study investigated the T2 spectrum of hydrogen nuclear magnetic resonance (1H NMR) signals in cement paste with water-to-cement ratios (w/c) of 0.2, 0.35, and 0.5 under three different saturation methods (natural soak, vacuum saturation, and vacuum saturation with high pressure). The saturation degree and pore structure of the cement paste under different saturation methods has been calculated through the linear relationship between water absorption and increment of NMR amplitude intensity. The results showed that the saturation degree of the cement paste increased progressively with the duration of saturation until it reached a state of equilibrium. It can increase saturation degree and reduce the saturation time by increasing the saturation pressure, and vacuum saturation with high pressure is necessary for cement paste with lower w/c. It is important to noted that conditions such as unsaturation, natural soak, and vacuum saturation may result in incomplete water saturation, leading to a partial loss of the 1H NMR signal amplitude intensity and underestimation of porosity measurements. Considering the duration of saturation and the degree of saturation, it is recommended a saturation duration of at least 4 h with a vacuum pressure of 8 MPa for cement paste with w/c ratio of 0.2 and 0.35. For cement paste with w/c of 0.5, a saturation duration of at least 0.5 h with a vacuum pressure of 8 MPa is suggested.

Synthesis and Conformational Analysis of α,β‐Dichlorocarbonyl Compounds

α,β‐Dichlorocarbonyl compounds were synthesized by facile dichlorination of α,β‐unsaturated amides with TCIA‐PPh3 and the resultant amides were converted to ketones. Conformational analyses of the products were performed to confirm our previous hypothesis regarding vicinal dichlorinated carbonyl compounds. The compounds exhibited 1H NMR signals with large coupling constants (7‐11 Hz) for the 1,2‐anti‐configuration and small coupling constants (3‐4 Hz) for the 1,2‐syn‐configuration. The syn‐pentane interaction enabled rational conformational analysis of the α,β‐dichlorinated carbonyl compounds, although some interesting exceptions were observed. Consideration of these conformations is helpful in assigning relative configurations of α,β‐dihalogenated carbonyl compounds in general.

Overcrowded 14,14'-Bidibenzo[a,j]anthracenes: Challenges in Syntheses and Atypical Property of Lacking Symmetry-Breaking Charge Transfer (SBCT).

14,14'-Bidibenzo[a,j]anthracenes (BDBAs) were prepared by iridium-catalyzed annulation of 5,5'-biterphenylene with alkynes. The molecular geometries of overcrowded BDBAs were verified by X-ray crystallography. The two dibenzo[a,j]anthryl moieties are connected through the sterically hindered 14 positions, resulting in highly distorted molecular halves. The conformation with a small twist angle between two molecular halves can minimize steric conflicts between the substituents at 1 and 13 positions and the carbon atoms of the central axis, as well as steric clashes between those substituents. One such example is octafluoro-substituted BDBA, where the interplanar angle between two anthryl moieties is approximately 31° (currently the lowest reported value, cf. 81° in 9,9'-bianthracene). The intramolecular interactions and electronic couplings between two molecular halves resulted in upfield 1H NMR signals, redshifted absorption and emission bands, and a reduced HOMO-LUMO gap. Photodynamic investigations on BDBAs indicated that the formation of the conventional symmetry-breaking charge transfer (SBCT) state was suspended by restricted rocking around the central C-C bond. Such a mechanism associated with this highly constrained conformation was examined for the first time.

Evaluation of DFT methods for predicting geometries and NMR spectra of Bi(III) dithiocarbamate complexes with antitumor properties.

Bismuth complexes with dithiocarbamate ligands have attracted attention because of their biological applications, such as antimicrobial, antileishmanial, and anticancer properties. These complexes have high cytotoxic activity against cancer cells, being more active than the standard drugs cisplatin, doxorubicin, and tamoxifen. In the present study, we investigated the ability of some DFT methods to reproduce the geometries and NMR spectra of the Bi(III) dithiocarbamate complexes, selected based on their proven antitumor activity. Our investigation revealed that the M06-L/def2-TZVP/ECP/CPCM method presented good accuracy in predicting geometries, while the TPSSh/def2-SVP/ECP/CPCM method proved effective in analyzing the 13C NMR spectra of these molecules. In general, all examined methods exhibited comparable performance in predicting 1H NMR signals. Calculations were performed with the Gaussian 09 program using the def2-SVP and def2-TZVP basis sets, employing relativistic effective core potential (ECP) for Bi and using the CPCM solvent model. The exchange-correlation functionals BP86, PBE, OLYP, M06-L, B3LYP, B3LYP-D3, M06-2X, TPSSh, CAM-B3LYP, and ωB97XD were used in the study. Geometry optimizations were started from crystallographic structures available at the Cambridge Structural Database. The theoretical results were compared with experimental data using the mean root-mean-square deviation (RMSD), mean absolute deviations (MAD), and linear correlation coefficient (R2).

Enantiospecific Analysis of Carboxylic Acids Using Cinchona Alkaloid Dimers as Chiral Solvating Agents.

Cinchona alkaloid derivatives as Brønsted base catalysts have attracted considerable attention in the field of asymmetric catalysis. However, their potential application as chiral solvating agents has not been described. In this research, we investigated the use of the Cinchona alkaloid dimer, namely, (DHQ)2PHAL, as a chiral solvating agent for discerning various mandelic acid derivatives through 1H NMR spectroscopy. The addition of catalytic amounts of DMAP facilitated this process. Our experimental results demonstrate that dimeric (DHQ)2PHAL exhibits remarkable chiral discrimination properties regarding the diagnostic split protons of 1H NMR signals (including 24 examples, up to 0.321 ppm). Furthermore, it serves as an excellent chiral discriminating agent and provides good resolution for racemic chiral phosphoric acid as determined by 31P NMR spectroscopy. The quality of enantiodifferentiation has also been evaluated by means of the parameter "resolution (Rs)". Significantly, this class of CSAs based on (alkaloid)2linker systems with an azaaromatic linker can be directly employed, which is commercially available in an enantiopure form at very low cost and exhibits promising potential in determining the enantiopurity of α-hydroxy acids by chemoselective and biocatalytic reactions.

Two fields are better than one – A multifunctional (semi)automated setup for quantitative measurements of parahydrogen-induced signal enhancement at low and high fields

The rapid advancement of parahydrogen-induced hyperpolarization (PHIP) and its diverse array of applications highlights the critical need for enhanced signals in both 1H NMR and heteronuclear NMR spectroscopy. Simultaneously, there is an increasing interest in utilizing benchtop NMR analysis across various laboratory settings. However, due to their lower magnetic fields, benchtop NMR spectrometers inherently produce weaker signal intensities. Here, PHIP is a well-established solution to this challenge. Consequently, we are expanding our cost-effective PHIP setup from a high-field NMR spectrometer (11.7 T) to include an additional benchtop NMR spectrometer (1.4 T), thereby enabling concurrent execution of PHIP experiments and measurements. Through the implementation of automated experimental protocols, we aim to minimize experiment time while increasing reproducibility. In this work, a non-isotope labelled propargyl alcohol sample is used at low concentrations to demonstrate our setup’s capabilities. It could be shown that single-scan PASADENA experiments can be run with comparable signal enhancements at the benchtop as well as the high-field spectrometer. At 1.4 T, fully automated PHIP pseudo-2D measurements will also be demonstrated. Additionally, two different field profiles for the spin-order transfer of p-H2 to 13C at zero- to ultralow fields are elaborated upon. The setup facilitates the measurement of carbon signal enhancement of more than 2000 on the benchtop NMR spectrometer, employing a straightforward one-pulse, one-scan experiment.

Synthesis, NMR, electronic properties using DFT study and anticancer activity of 3-methyl-6-(m-tolylamine) quinazolin-4(3H)-one

3-methyl-6-(m-tolylamine) quinazolin-4(3H)-one (MTAQ) was synthesized. Its formation was ascertained with the help ESI mass spectroscopy in conjunction with 1HNMR spectroscopy. Anticancer activity of MTAQ was measured experimentally, for human carcinoma cell line pertaining to cervix (HeLa). Optimized structure parameters, Frontier molecular orbital (FMO) behavior, non linear optical (NLO) profile, molecular electrostatic potential surface (MESP), Fukui functions (FF) and thermodynamic parameters were evaluated for the molecule of interest employing DFT/B3LYP/6–311++G(d,p) formalism. TD-DFT was made use of to calculate absorption maxima (λmax) of electronic transitions for the molecule in CDCl3 solvent. Frontier molecular orbitals revealed the origin of UV–Vis spectrum and to comprehend chemical reactivity of the molecule. Good coincidence was noticed between measured and computed structure parameters, UV–Vis spectra, and 1HNMR signals. Fukui functions helped in identifying electrophilic and nucleophilic centers of MTAQ. The calculations showed that MTAQ exhibits significant NLO activity in addition to predicting existence of intramolecular hydrogen bond.

From Stilbenes to carbo-Stilbenes: an Encouraging Prospect.

Beyond previously described carbo-naphthalene and carbo-biphenyl, a novel type of bis-carbo-benzenic molecules is envisaged from the stilbene parent. The synthesis, structure, spectroscopic and electrochemical properties of two such carbo-stilbenes are described at complementary experimental and computational DFT levels. In the selected targets, the bare skeletal carbo-mer of carbo-stilbene is decorated by 8 or 10 phenyl groups, 0 or 2 tert-butyl groups, and 2 n-octyl chains, the later substituents being introduced to compensate anticipated solubility issues. As in the parent stilbene series, isomers of the phenylated carbo-stilbenes are characterized. The cis- and trans-isomers are, however, formed in almost equal amounts and could not be separated by either chromatography or crystallization. Nevertheless, due to a slow interconversion at the NMR time scale (up to 55 °C) the 1H NMR signals of both isomers of the two carbo-stilbenes could be tentatively assigned. The calculated structure of the cis-isomer exhibits a helical shape, consistent with the observed magnetic shielding of phenyl p-CH nuclei residing inside the shielding cone of the facing C18 ring. The presence of the two isomers in solution also gives rise to quite broad UV-vis absorption spectra with main bands at ca 460, 560 and 710 nm, and a significant bathochromic shift for the decaphenylated carbo-stilbene vs the di-tert-butyl-octaphenylated counterpart. Square wave voltammograms do not show any resolution of the two isomers, giving a reversible reduction wave at -0.65 or -0.58 V/SCE, and an irreversible oxidation peak at 1.11 V/SCE, those values being classical for most carbo-benzene derivatives. Calculated NICS values (NICS(1)=-12.5±0.2 ppm) also indicate that the aromatic nature of the C18 rings is not markedly affected by the dialkynylbutatriene (DAB) connector between them.