Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the ...Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the absence of the first-order quadrupolar broadenings.In addition,^(14)N^(OT) allows selective manipulation of ^(14)N nuclei for each site.Despite extensive theoretical and experimental studies,the spin dynamics of ^(14)N^(OT) remains under debate.In this study,we conducted experimental investigations to assess the spin dynamics of ^(14)N^(OT) using the rotational-echo saturation-pulse double-resonance(RESPDOR)sequence,which monitors population transfer induced by a^(14)N^(OT) pulse.The ^(14)N^(OT) spin dynamics is well represented by a model of a two-energy-level system.Unlike spin-1/2,the maximum excitation efficiency of ^(14)N^(OT) coherences of powdered solids,denoted by p,depends on the radiofrequency field(rf-field)strength due to orientation dependence of effective nutation fields even when pulse lengths are optimized.It is also found that the p factor,contributing to the ^(14)N^(OT) spin dynamics,is nearly independent of the B0 field.Consequently,the filtering efficiency of RESPDOR experiments exhibits negligible dependence on B0 when the ^(14)N^(OT) pulse length is optimized.The study also identifies the optimal experimental conditions for ^(14)N^(OT)/^(1)H RESPDOR correlation experiments.展开更多
Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical...Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical shifts （δH（CH=N）） and 13C NMR chemical shifts （δc（CH=N）） of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show thatthe substituent specific cross-interaction effect parameter （△（∑σ）2） plays an important role in quantifying the δc（CH=N） values of XBAYs, but it is negligible for quantifying the δH （CH=N） values; the other substituent parameters also present different influences on the δc （CH=N） and （δH （CH=N）. On the whole, the contributions of X and Y to the δc （CH=N） of XBAYs are balanced, but the δH（CH=N） values of XBAYs mainly rely on the contributions of X.展开更多
To raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a noncrystalline two-component epoxy electrolyte system has been prepared. The diglycidyl ether ...To raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a noncrystalline two-component epoxy electrolyte system has been prepared. The diglycidyl ether of polyethylene glycols as precursors of the system were synthesized by a two-step process. The presumed structure of the product was characterized, by ^(13)C, ~1H NMR and IR spectroscopy. It was found that a side-reaction occurred between the secondary hydroxyl group of PEG-chlorohydrin and epichlorohydrin in some degree, resulting in a by- product containing—CH_2Cl side group. By selecting a characteristic signal, which is undistorted by the increase in the length of CH_2 CH_2—O segment, a ~1H NMR approach of determining the equivalent epoxy weight (EEW) was proposed. The method is valid to specimens even though the EEW is as high as 2,000. The examination of the specimens by DSC showed that epoxidation greatly depressed the crystallinity of the PEG's, whereas the T_g was raised.展开更多
Experiments including C-13 spin-lattice relaxation, C-13 heteronuclear dipolar dephasing and H-1 spin diffusion are performed on poly (2,6-dimethyl-1,4-phenylene oxide) (PPO). The results show that the rotation of the...Experiments including C-13 spin-lattice relaxation, C-13 heteronuclear dipolar dephasing and H-1 spin diffusion are performed on poly (2,6-dimethyl-1,4-phenylene oxide) (PPO). The results show that the rotation of the methyl groups in solid PPO is partially restricted, which results in a surprisingly efficient spin diffusion between the aromatic proton and methyl proton characterized by a diffusion time of 150 mu s. The results also show that the aromatic ring in solid PPO is rigid and twisted, which causes all aromatic carbons to be chemically unequivalent.展开更多
Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities an...Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities and degradation products whereas basic degradation studies show new impurity which has higher molecular weight than Lansoprazole. New impurity was identified, isolated using mass based auto purification system and characterised by 1H NMR, 13C NMR, HMBC, HSQC, NOE, COSY and HRMS experiments. Isolated impurity was showing molecular weight of 467.10, molecular formula of C23H16F3N5OS and its name is 7-(3-Methyl-4-(2,2,2-trifluoroethoxy) pyridin-2-yl)-7H-benzo[4,5]imidazo[2,1-b]benzo[4,5]imidazo[2,1-d][1,3,5]thiadiazine.展开更多
The polysaccharide was isolated from Hypnea pannosa which was grown in Okinawa, Japan. The yield of the polysaccharide was 17.2%, and the total carbohydrates, pyruvic acid, sulfuric acid and ash contents were 55.2%, 3...The polysaccharide was isolated from Hypnea pannosa which was grown in Okinawa, Japan. The yield of the polysaccharide was 17.2%, and the total carbohydrates, pyruvic acid, sulfuric acid and ash contents were 55.2%, 3.8%, 35.2% and 24.3%, respectively. 3,6-Anhydro-α-D-galactose, β-D-galactose, α-D-galactose and D-glucose were identified by liquid and thin-layer chromatography. Fourier transform infrared (FTIR) spectra of the polysaccharide resembled that of ι-carrageenan. From the <sup>1</sup>H- and <sup>13</sup>C-NMR spectra, 1,3-linked β-D-galactose, 1,4-linked anhydro-α-D-galactose, 1,4-linked α-D-galactose, 1,4-linked β-D-glucose and pyruvic acid (carboxyl acetal, methyl proton and methyl carbon) were assigned. Methylation analysis revealed terminal D-galactose 0.1 mol), 1,4-linked D-glucose (1.0 mol) and 1,2,3,4,6-linked D-galactose (3.7 mol) for native polysaccharide, and terminal D-galactose, 1,4-linked D-galactose (1.9 mol), 1,4-linked D-glucose (1.0 mol), 1,3- linked D-galactose (1.7 mol), and 1,3,4,6-linked D-galactose (0.3 mol) which substituted with pyruvate group at 4 and 6 positions for desulfated polysaccharide. The polysaccharide was the novel pyruvated glucogalactan sulfate, the structure of which was proposed.展开更多
In this paper the spectroscopic and the geometric properties of four ligands with pyrazole unit are studied at both experimental and computational levels.The computational results are perfectly in good agreement with ...In this paper the spectroscopic and the geometric properties of four ligands with pyrazole unit are studied at both experimental and computational levels.The computational results are perfectly in good agreement with the experimental results especially in terms of the IR,1 H-NMR and 13 C-NMR shifts.The spectroscopic features as well as the computed properties help to establish the successful synthesis of ligands bdmpzm and bdmpza.The theoretical and the experimental IR and Raman significantly help in distinguishing the four ligands.The results show that the Raman spectral is better applicable in characterising the CH3deformation,the C-H,CNN and CCNNout of the ligands but vibrations like N-H in dmpz and O-H,CO in bdmpza are observed to be Raman inactive.A significant variations are observed among the two available*N atoms characterising the bidentate features of bdmpzm,bdmpza and bdcpzm which indicates a possible different affinities for metal coordination.Also the result suggest that bdmpza will be the best starting material for NLO application than other while bdcpzm is predicted to have potential of been a poor coordinating ligand.The computed variations in the properties of*N atoms that are the characteristic features of their power of coordination can be of immense help since these type of ligands have a wide application in transition metal coordination.展开更多
The morphology of some polyetherester-ureas were studied by ^(13)C CP/MAS and ~1H wide-line NMR spectroscopy. It was found that the HDI and MDI based polymers have well crystallized hard segments, whereas the TDI and ...The morphology of some polyetherester-ureas were studied by ^(13)C CP/MAS and ~1H wide-line NMR spectroscopy. It was found that the HDI and MDI based polymers have well crystallized hard segments, whereas the TDI and HMDI based ones have not. For HDI/MDI based polymers, the presented results suggest that the distribution of two kinds of hard segment units is mainly in a block form. The influences of the different hard segment and chain length on the mobility of the soft segment were also studied.展开更多
In this paper, the assignment of acomplex 8-spin-half system （7,7-dichloro-6-oxo-2-tio-bicycle [3.2.0] heptane-4-carboxlic acid） using nuclear magnetic resonance （NMR） techniques is presented and the hamiltonian o...In this paper, the assignment of acomplex 8-spin-half system （7,7-dichloro-6-oxo-2-tio-bicycle [3.2.0] heptane-4-carboxlic acid） using nuclear magnetic resonance （NMR） techniques is presented and the hamiltonian obtained, was used to demonstrate universal control. The system has 313C and 51H,in our work, we carried out traditional 1-D and 2-D experiments and also made use of coherent control together with simulation to get the full hamiltonian of this weakly coupled system. Spin-echo J-resolved 2-D experiments were used to obtain the heteronuclear and homonuclear coupling values; COSY45 experiments were used to obtain the signs of homonuclear coupling constants. The signs of heteronuclear coupling constants were obtained using the polarization transfer method. All the data obtained in the experiments were used in the simulation of the 1-D spectra and then optimized using the least square fitting method. After obtaining the full hamiltonian of the 8-spin system, we used it in QIP, prepared pseudopure states and implemented 1-qubit and 2-qubit gates on one of its 6-qubit subsystems.展开更多
文摘Nitrogen-14(^(14)N)overtone(OT)spectroscopy under fast magic angle spinning(MAS)conditions(>60 kHz)has emerged as a powerful technique for observing correlations and distances between ^(14)N and ^(1)H,owing to the absence of the first-order quadrupolar broadenings.In addition,^(14)N^(OT) allows selective manipulation of ^(14)N nuclei for each site.Despite extensive theoretical and experimental studies,the spin dynamics of ^(14)N^(OT) remains under debate.In this study,we conducted experimental investigations to assess the spin dynamics of ^(14)N^(OT) using the rotational-echo saturation-pulse double-resonance(RESPDOR)sequence,which monitors population transfer induced by a^(14)N^(OT) pulse.The ^(14)N^(OT) spin dynamics is well represented by a model of a two-energy-level system.Unlike spin-1/2,the maximum excitation efficiency of ^(14)N^(OT) coherences of powdered solids,denoted by p,depends on the radiofrequency field(rf-field)strength due to orientation dependence of effective nutation fields even when pulse lengths are optimized.It is also found that the p factor,contributing to the ^(14)N^(OT) spin dynamics,is nearly independent of the B0 field.Consequently,the filtering efficiency of RESPDOR experiments exhibits negligible dependence on B0 when the ^(14)N^(OT) pulse length is optimized.The study also identifies the optimal experimental conditions for ^(14)N^(OT)/^(1)H RESPDOR correlation experiments.
基金supported by the National Natural Science Foundation of China(No.21672058 and No.21272063)
文摘Fifty-three samples of multi-substituted benzylideneanilines XArCH=NArYs （abbreviated XBAYs） were synthesized and their NMR spectra were determined. An extensional study of substituent effects on the 1H NMR chemical shifts （δH（CH=N）） and 13C NMR chemical shifts （δc（CH=N）） of the CH=N bridging group from di-substituted to multi-substituted XBAYs was made based on a total of 182 samples of XBAYs, together with the NMR data of other 129 samples of di-substituted XBAYs quoted from literatures. The results show thatthe substituent specific cross-interaction effect parameter （△（∑σ）2） plays an important role in quantifying the δc（CH=N） values of XBAYs, but it is negligible for quantifying the δH （CH=N） values; the other substituent parameters also present different influences on the δc （CH=N） and （δH （CH=N）. On the whole, the contributions of X and Y to the δc （CH=N） of XBAYs are balanced, but the δH（CH=N） values of XBAYs mainly rely on the contributions of X.
基金The project supported by National Natural Science Foundation of China.
文摘To raise the room temperature ionic conductivity and improve the mechanical strength of a PEO-based polymer electrolyte, a noncrystalline two-component epoxy electrolyte system has been prepared. The diglycidyl ether of polyethylene glycols as precursors of the system were synthesized by a two-step process. The presumed structure of the product was characterized, by ^(13)C, ~1H NMR and IR spectroscopy. It was found that a side-reaction occurred between the secondary hydroxyl group of PEG-chlorohydrin and epichlorohydrin in some degree, resulting in a by- product containing—CH_2Cl side group. By selecting a characteristic signal, which is undistorted by the increase in the length of CH_2 CH_2—O segment, a ~1H NMR approach of determining the equivalent epoxy weight (EEW) was proposed. The method is valid to specimens even though the EEW is as high as 2,000. The examination of the specimens by DSC showed that epoxidation greatly depressed the crystallinity of the PEG's, whereas the T_g was raised.
文摘Experiments including C-13 spin-lattice relaxation, C-13 heteronuclear dipolar dephasing and H-1 spin diffusion are performed on poly (2,6-dimethyl-1,4-phenylene oxide) (PPO). The results show that the rotation of the methyl groups in solid PPO is partially restricted, which results in a surprisingly efficient spin diffusion between the aromatic proton and methyl proton characterized by a diffusion time of 150 mu s. The results also show that the aromatic ring in solid PPO is rigid and twisted, which causes all aromatic carbons to be chemically unequivalent.
文摘Lansoprazole degradation is accelerated in both acidic and basic medium in water. The present investigation deals with the hydrolytic degradation of Lansoprazole. Acidic medium degradation show all known impurities and degradation products whereas basic degradation studies show new impurity which has higher molecular weight than Lansoprazole. New impurity was identified, isolated using mass based auto purification system and characterised by 1H NMR, 13C NMR, HMBC, HSQC, NOE, COSY and HRMS experiments. Isolated impurity was showing molecular weight of 467.10, molecular formula of C23H16F3N5OS and its name is 7-(3-Methyl-4-(2,2,2-trifluoroethoxy) pyridin-2-yl)-7H-benzo[4,5]imidazo[2,1-b]benzo[4,5]imidazo[2,1-d][1,3,5]thiadiazine.
文摘The polysaccharide was isolated from Hypnea pannosa which was grown in Okinawa, Japan. The yield of the polysaccharide was 17.2%, and the total carbohydrates, pyruvic acid, sulfuric acid and ash contents were 55.2%, 3.8%, 35.2% and 24.3%, respectively. 3,6-Anhydro-α-D-galactose, β-D-galactose, α-D-galactose and D-glucose were identified by liquid and thin-layer chromatography. Fourier transform infrared (FTIR) spectra of the polysaccharide resembled that of ι-carrageenan. From the <sup>1</sup>H- and <sup>13</sup>C-NMR spectra, 1,3-linked β-D-galactose, 1,4-linked anhydro-α-D-galactose, 1,4-linked α-D-galactose, 1,4-linked β-D-glucose and pyruvic acid (carboxyl acetal, methyl proton and methyl carbon) were assigned. Methylation analysis revealed terminal D-galactose 0.1 mol), 1,4-linked D-glucose (1.0 mol) and 1,2,3,4,6-linked D-galactose (3.7 mol) for native polysaccharide, and terminal D-galactose, 1,4-linked D-galactose (1.9 mol), 1,4-linked D-glucose (1.0 mol), 1,3- linked D-galactose (1.7 mol), and 1,3,4,6-linked D-galactose (0.3 mol) which substituted with pyruvate group at 4 and 6 positions for desulfated polysaccharide. The polysaccharide was the novel pyruvated glucogalactan sulfate, the structure of which was proposed.
基金financial support of Govan Mbeki Research and Development Centre,University of Fort Hare,South Africa
文摘In this paper the spectroscopic and the geometric properties of four ligands with pyrazole unit are studied at both experimental and computational levels.The computational results are perfectly in good agreement with the experimental results especially in terms of the IR,1 H-NMR and 13 C-NMR shifts.The spectroscopic features as well as the computed properties help to establish the successful synthesis of ligands bdmpzm and bdmpza.The theoretical and the experimental IR and Raman significantly help in distinguishing the four ligands.The results show that the Raman spectral is better applicable in characterising the CH3deformation,the C-H,CNN and CCNNout of the ligands but vibrations like N-H in dmpz and O-H,CO in bdmpza are observed to be Raman inactive.A significant variations are observed among the two available*N atoms characterising the bidentate features of bdmpzm,bdmpza and bdcpzm which indicates a possible different affinities for metal coordination.Also the result suggest that bdmpza will be the best starting material for NLO application than other while bdcpzm is predicted to have potential of been a poor coordinating ligand.The computed variations in the properties of*N atoms that are the characteristic features of their power of coordination can be of immense help since these type of ligands have a wide application in transition metal coordination.
文摘The morphology of some polyetherester-ureas were studied by ^(13)C CP/MAS and ~1H wide-line NMR spectroscopy. It was found that the HDI and MDI based polymers have well crystallized hard segments, whereas the TDI and HMDI based ones have not. For HDI/MDI based polymers, the presented results suggest that the distribution of two kinds of hard segment units is mainly in a block form. The influences of the different hard segment and chain length on the mobility of the soft segment were also studied.
文摘In this paper, the assignment of acomplex 8-spin-half system （7,7-dichloro-6-oxo-2-tio-bicycle [3.2.0] heptane-4-carboxlic acid） using nuclear magnetic resonance （NMR） techniques is presented and the hamiltonian obtained, was used to demonstrate universal control. The system has 313C and 51H,in our work, we carried out traditional 1-D and 2-D experiments and also made use of coherent control together with simulation to get the full hamiltonian of this weakly coupled system. Spin-echo J-resolved 2-D experiments were used to obtain the heteronuclear and homonuclear coupling values; COSY45 experiments were used to obtain the signs of homonuclear coupling constants. The signs of heteronuclear coupling constants were obtained using the polarization transfer method. All the data obtained in the experiments were used in the simulation of the 1-D spectra and then optimized using the least square fitting method. After obtaining the full hamiltonian of the 8-spin system, we used it in QIP, prepared pseudopure states and implemented 1-qubit and 2-qubit gates on one of its 6-qubit subsystems.
