Abstract:The methods used here, particularly the 2D SSNMR methods based on spin diffusion, provided detailed structural information about a nanocrystalline polymer dispersion of ebselen, and should be useful in other studies of these types of materials.
“…PXRD pattern of H 2 SeO 3
1 is completely different from that of PhSeO 2 H 2 , confirming their different crystal structures due to the presence of a benzene ring 47 . In contrast, all the polymer materials exhibit a broad reflection, indicating their amorphous structures 48 .Figure 1PXRD patterns: ( a ) H 2 SeO 3
1 ; ( b ) PhSeO 2 H 2 ; ( c–e ) Polymers 4 – 6 .
…”
Section: Resultsmentioning
confidence: 99%
“…The broadening of the 77 Se peak might be attributed to chemical shift distribution 52 . The chemical shift distribution might be originated from the change in solid-state from more ordered crystalline to amorphous structures 38, 47, 48 . This explanation can be well supported by PXRD results (Fig.…”
Characterization of selenium states by 77Se NMR is quite important to provide vital information for mechanism studies in organoselenium-catalyzed reactions. With the development of heterogeneous polymer-supported organoselenium catalysts, the solid state 77Se NMR comes to the spotlight. It is necessary to figure out an advanced protocol that provides good quality spectra within limited time because solid state 77Se NMR measurements are always time consuming due to the long relaxation time and the relatively low sensitivity. Studies on small molecules and several novel polymer-supported organoselenium materials in this article showed that cross polarization (CP) method with the assistance of magic angle spinning (MAS) was more efficient to get high quality spectra than the methods by using single pulse (SP) or high power 1H decoupling (HPHD) combined with MAS. These results lead to a good understanding of the effect of the molecular structure, the heteronuclear coupling, the long-range ordering of the solid (crystal or amorphous), and the symmetry of 77Se on quality of their spectra.
“…PXRD pattern of H 2 SeO 3
1 is completely different from that of PhSeO 2 H 2 , confirming their different crystal structures due to the presence of a benzene ring 47 . In contrast, all the polymer materials exhibit a broad reflection, indicating their amorphous structures 48 .Figure 1PXRD patterns: ( a ) H 2 SeO 3
1 ; ( b ) PhSeO 2 H 2 ; ( c–e ) Polymers 4 – 6 .
…”
Section: Resultsmentioning
confidence: 99%
“…The broadening of the 77 Se peak might be attributed to chemical shift distribution 52 . The chemical shift distribution might be originated from the change in solid-state from more ordered crystalline to amorphous structures 38, 47, 48 . This explanation can be well supported by PXRD results (Fig.…”
Characterization of selenium states by 77Se NMR is quite important to provide vital information for mechanism studies in organoselenium-catalyzed reactions. With the development of heterogeneous polymer-supported organoselenium catalysts, the solid state 77Se NMR comes to the spotlight. It is necessary to figure out an advanced protocol that provides good quality spectra within limited time because solid state 77Se NMR measurements are always time consuming due to the long relaxation time and the relatively low sensitivity. Studies on small molecules and several novel polymer-supported organoselenium materials in this article showed that cross polarization (CP) method with the assistance of magic angle spinning (MAS) was more efficient to get high quality spectra than the methods by using single pulse (SP) or high power 1H decoupling (HPHD) combined with MAS. These results lead to a good understanding of the effect of the molecular structure, the heteronuclear coupling, the long-range ordering of the solid (crystal or amorphous), and the symmetry of 77Se on quality of their spectra.
“…Even though some correlation reported between FWHM of SS‐NMR signal and size of crystalline domain, further investigation is necessary to unravel various contributing effects to such broadening. Vogt and Williams have shown the superiority of 13 C and 77 Se one‐dimensional SS‐NMR spectroscopy as well as two‐dimensional 1 H spin diffusion spectroscopy in understanding the physical structure of nanocrystalline dispersions of ebselen in PVP/VA 64 compared with pXRD.…”
Section: Crystallinity/crystallization Studies In Asd By Ss‐nmr Spectmentioning
“…Raman mapping has now become an essential analytical method in pharmaceutical applications as it can provide a unique combination for probing the chemical and structural properties of a sample at a micro‐scale (µm) simultaneously. The original mapping spectra generally contain both qualitative and quantitative information for identification and quantification of crystalline API.…”
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