“…The optimal relaxation delay was found to be 40 s. Much attention has been paid recently to deuterium high-resolution NMR spectroscopy as an alternative technique to the quadrupolar echo experiment. [34][35][36][37] Figure 11a displays the 1 H-2 H CP/ MAS spectrum of 1c unexpectedly, with signal only from the CD 3 group.…”
Section: Resultsmentioning
confidence: 99%
“…Unfortunately, this experiment requires a long time accumulation in order to achieve a sufficient signal-to-noise ratio (2K scans). The optimal relaxation delay was found to be 40 s. Much attention has been paid recently to deuterium high-resolution NMR spectroscopy as an alternative technique to the quadrupolar echo experiment. − Figure a displays the 1 H− 2 H CP/MAS spectrum of 1c unexpectedly, with signal only from the CD 3 group. 11 VT 1 H− 2 H CP/MAS experimental spectra of toluene- d 8 occluded in the crystal lattice of 1b .…”
Anhydro-2-O-tosyl-4-S-(5,5-dimethyl-2-thioxa-1,3,2-dioxaphosphorinan-2-yl)-β-D-glucopyranose (1, C 18 H 25 O 8 PS 3 ), crystallized from polar and/or nonpolar solvents, forms different modifications in the solid phase. Crystal structures of 1 (obtained from a methanol solution) and its 2-propanol solvate (1a) were established by X-ray structure analysis at low temperature. One-component crystal 1 is orthorhombic, space group and D c ) 1.457 g cm -3 . Refinement of 275 parameters using 2661 observed reflections (I > 2σ(I)) converged at R(F) ) 0.0372. The crystal of 1a is an inclusion structure containing molecules of 1 and 2-propanol in the ratio 1/1; crystals are triclinic, space group P1, with a ) 9.637(6) Å, b ) 9.709(6) Å, c ) 8.865(8) Å, R ) 110.27(5)°, β ) 106.33(5)°, γ ) 108.70(6)°, V ) 661.3(8) Å 3 , Z ) 1, and D c ) 1.398 g cm -3 . Full-matrix least-squares refinement of 307 parameters using 2478 observed reflections gave final R(F) ) 0.0349. Intermolecular hydrogen bonds (O-H‚‚‚O, C-H‚‚‚O in 1; O-H‚‚‚O, O-H‚‚‚S in 1a) are present along with the C-H‚‚‚SdP intermolecular interactions. A search of Cambridge Structural Database shows that such contacts are not unusual for organothiophosphoryl compounds. The solid-state structures were studied by the NMR spectroscopy. The analysis of the 31 P chemical shift parameters enabled the correlation of the δ 33 principal element of chemical shift tensor and span (Ω) with C-H‚‚‚SdP contact. The presence of toluene-d 8 in the crystal lattice of inclusion complex 1b was confirmed by 2 H NMR spectroscopy.
“…The optimal relaxation delay was found to be 40 s. Much attention has been paid recently to deuterium high-resolution NMR spectroscopy as an alternative technique to the quadrupolar echo experiment. [34][35][36][37] Figure 11a displays the 1 H-2 H CP/ MAS spectrum of 1c unexpectedly, with signal only from the CD 3 group.…”
Section: Resultsmentioning
confidence: 99%
“…Unfortunately, this experiment requires a long time accumulation in order to achieve a sufficient signal-to-noise ratio (2K scans). The optimal relaxation delay was found to be 40 s. Much attention has been paid recently to deuterium high-resolution NMR spectroscopy as an alternative technique to the quadrupolar echo experiment. − Figure a displays the 1 H− 2 H CP/MAS spectrum of 1c unexpectedly, with signal only from the CD 3 group. 11 VT 1 H− 2 H CP/MAS experimental spectra of toluene- d 8 occluded in the crystal lattice of 1b .…”
Anhydro-2-O-tosyl-4-S-(5,5-dimethyl-2-thioxa-1,3,2-dioxaphosphorinan-2-yl)-β-D-glucopyranose (1, C 18 H 25 O 8 PS 3 ), crystallized from polar and/or nonpolar solvents, forms different modifications in the solid phase. Crystal structures of 1 (obtained from a methanol solution) and its 2-propanol solvate (1a) were established by X-ray structure analysis at low temperature. One-component crystal 1 is orthorhombic, space group and D c ) 1.457 g cm -3 . Refinement of 275 parameters using 2661 observed reflections (I > 2σ(I)) converged at R(F) ) 0.0372. The crystal of 1a is an inclusion structure containing molecules of 1 and 2-propanol in the ratio 1/1; crystals are triclinic, space group P1, with a ) 9.637(6) Å, b ) 9.709(6) Å, c ) 8.865(8) Å, R ) 110.27(5)°, β ) 106.33(5)°, γ ) 108.70(6)°, V ) 661.3(8) Å 3 , Z ) 1, and D c ) 1.398 g cm -3 . Full-matrix least-squares refinement of 307 parameters using 2478 observed reflections gave final R(F) ) 0.0349. Intermolecular hydrogen bonds (O-H‚‚‚O, C-H‚‚‚O in 1; O-H‚‚‚O, O-H‚‚‚S in 1a) are present along with the C-H‚‚‚SdP intermolecular interactions. A search of Cambridge Structural Database shows that such contacts are not unusual for organothiophosphoryl compounds. The solid-state structures were studied by the NMR spectroscopy. The analysis of the 31 P chemical shift parameters enabled the correlation of the δ 33 principal element of chemical shift tensor and span (Ω) with C-H‚‚‚SdP contact. The presence of toluene-d 8 in the crystal lattice of inclusion complex 1b was confirmed by 2 H NMR spectroscopy.
“…38,39 Under sample spinning conditions, the deuterium spectrum is composed of center and sidebands with well-defined intensities spanning the frequency range of this pattern. 40 Molecular motion influences these intensities and the widths of these bands without changing their frequency positions. Molecular reorientation that is very fast in the NMR time scale averages the quadrupolar interactions leading to the liquid-like deuterium spectra.…”
In this work, we report drug-loading procedure based on the solid state thermal transformation of a physical mixture of two ingredients: mesoporous silica nanoparticles (MSN) and an organic cocrystal. This procedure, known as the melting method, allows loading of the guest species into the host pores with high yield and an equimolar ratio of both components of the cocrystal. The study was carried out with commercial MSNs (MCM-41 and SBA-15) and a cocrystal consisting of equimolar amounts of benzoic acid (BA) and fluorinated benzoic acid (FBA). The BA/FBA sample was obtained by grinding crystalline acids. The structural constraints and molecular dynamics of BA/FBA in the crystal lattice were characterized employing 19 F magic angle spinning (MAS), 13 C MAS, 1 H very fast (VF) MAS with sample rotation at 60 kHz, 2D NMR, 19 F− 19 F BABA, and 1 H− 19 F HETCOR correlations. We conclude that the system is very rigid with short distances between intermolecular aromatic layers. In contrast, BA/FBA loaded into MCM-41 and SBA-15 is very mobile in a broad range of temperatures. The structure and molecular dynamics of the guest assembly trapped in the MSN pores was established by 1 H MAS, 19 F MAS, 1 H− 19 F HOESY MAS and 19 F T 2 ′ relaxation time measurements as well as 2 H MAS. We conclude that the filling factor for the melting method, defined as the ratio of BA/FBA to MSN (weight to weight), is much higher compared to those for commonly used wet procedures. These results show new perspectives for future applications of MSNs as carriers of pharmaceutical cocrystals.
“…Mu ¨ller first demonstrated the possibility of performing 2 H CPMAS in 1981, 7 and since then, there have been theoretical and experimental studies on model compounds. 8,9 Zumbulyadis used 2 H-{ 1 H} CPMAS to study the miscibility of polymer blends, 10 and Poupko and co-workers employed 2 H-{ 1 H} CPMAS to study deuterons at natural abundance. 11 We recently used this technique to study as-made zeolites and employed it in heteronuclear correlation spectroscopy (HETCOR).…”
Section: Introductionmentioning
confidence: 99%
“…The small QCC combined with the ability to selectively label molecules with deuterium could make 2 H−{ 1 H} CPMAS desirable for studying organic and/or inorganic−organic composite systems. Müller first demonstrated the possibility of performing 2 H CPMAS in 1981, and since then, there have been theoretical and experimental studies on model compounds. , Zumbulyadis used 2 H−{ 1 H} CPMAS to study the miscibility of polymer blends, and Poupko and co-workers employed 2 H−{ 1 H} CPMAS to study deuterons at natural abundance . We recently used this technique to study as-made zeolites and employed it in heteronuclear correlation spectroscopy (HETCOR). , Here, we wish to focus on some of the experimental considerations necessary to successfully employ 2 H−{ 1 H} CPMAS in correlation spectroscopy and to show how experimental and physical parameters (spin rate, RF field strength, 1 H homonuclear dipole−dipole coupling, and the magnitude of the quadrupole frequency) affect the experimental results.…”
The feasibility of 2H−{1H} cross-polarization magic-angle spinning (CPMAS) NMR and its implementation
in HETCOR experiments is studied using as-made all-silica zeolites. The results presented show that 2H−{1H} CPMAS can be employed successfully in two-dimensional correlation spectroscopy experiments. The
effects of experimental and physical parameters (spin rate, RF field strengths, 1H homonuclear dipole−dipole
coupling, and the magnitude of the quadrupole coupling constants) on the NMR spectra are studied in detail.
In the limit of small quadrupole coupling constants and weak proton homonuclear dipolar coupling, the cross-polarization behavior of the deuterons is similar to spin I = 1/2 systems and proton spin-diffusion is minimal.
Samples with larger quadrupole coupling constants and strong proton dipole−dipole coupling exhibit less
efficient spin-locking of the deuterons and proton spin-diffusion is more prevalent. In this case, it is necessary
to perform proton spin-diffusion experiments in conjunction with the correlation spectroscopy. Minimizing
proton spin-diffusion is crucial for correct interpretation of the multidimensional correlation spectroscopy
experiments, which can be achieved for the samples studied here by using short contact times. 2H−{1H}
CPMAS HETCOR experiments could find uses for both organic and organic−inorganic solids where selective
deuteration can be achieved.
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