Infrared spectra of edge-shared silicate tetrahedra

Bunker, Bruce C.; Haaland, David M.; Ward, Kenneth; Michalské, Terry A.; Smith, William L.; Binkley, J. Stephen; Melius, Carl F.; Balfe, Carol A.

doi:10.1016/0039-6028(89)90603-1

Cited by 117 publications

(139 citation statements)

References 19 publications

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“…[8] With (SiO) 3 rings, this happens to a far lesser extent, whereas higher nuclearity (SiO) n > 3 rings, which are the basic constituent of amorphous silica, are almost unreactive. Quantum mechanical calculations [9][10][11] have confirmed the hypothesised (SiO) 2 structure and also showed great reactivity towards hydrogen-containing molecules, in agreement with the experimental evidence.…”

Section: Introductionsupporting

confidence: 84%

Does Silica Surface Catalyse Peptide Bond Formation? New Insights from First‐Principles Calculations

Rimola¹,

Tosoni²,

Sodupe³

et al. 2006

ChemPhysChem

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The role that silica surface could have played in prebiotic chemistry as a catalyst for peptide bond formation has been addressed at the B3LYP/6-31+G(d,p) level for a model reaction involving glycine and ammonia on a silica cluster mimicking an isolated terminal silanol group present at the silica surface. Hydrogen-bond complexation between glycine and the silanol is followed by the formation of the mixed surface anhydride Si(surf)-O-C(=O)-R, which has been suggested in the literature to activate the C=O bond towards nucleophilic attack by a second glycine molecule, here simulated by the simpler NH3 molecule. However, B3LYP/6-31+G(d,p) calculations show that formation of the surface mixed anhydride Si(surf)-O-C(=O)-R is disfavoured (delta(r)G298 approximately 6 kcal mol(-1)), and that the surface bond only moderately lowers the free-energy barrier of the nucleophilic attack responsible for peptide bond formation (deltaG298(double dagger) approximately 48 kcal mol(-1)) in comparison with the uncatalysed reaction (deltaG298(double dagger) approximately 52 kcal mol(-1)). A further decrease of the free-energy barrier of peptide bond formation (deltaG298(double dagger) approximately 41 kcal mol(-1)) is achieved by a single water molecule close to the reaction centre acting as a proton-transfer helper in the activated complex. A possible role of strained silica surface defects on the formation of the surface mixed anhydride Si(surf)-O-C(=O)-R has also been addressed.

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Section: Introductionsupporting

confidence: 84%

Does Silica Surface Catalyse Peptide Bond Formation? New Insights from First‐Principles Calculations

Rimola¹,

Tosoni²,

Sodupe³

et al. 2006

ChemPhysChem

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“…In fact, in silica glasses derived from solÈgels, the 606 cm~1 band is very strong and decreases in intensity with annealing. 58,59 The intensity of the band is also enhanced in the D 2 high-pressure Raman spectra of (Fig. 6) Si 4 O 9 cm~1 which has been tentatively assigned to the vibration within the wadeite threel s (SiÈOÈSi) membered rings.52 If this mechanism of formation of three-membered rings in silicate and germanate glasses at high pressure is correct, the increase in the intensity of the band with pressure would indicate the onset D 2 of change in the coordination of some T cations to V or VI.…”

Section: General Notes On the Origin Of Vibrational Bands In Glassesmentioning

confidence: 97%

Raman band assignments of silicate and germanate glasses using high-pressure and high-temperature spectral data

Sharma

Cooney

Wang

et al. 1997

J. Raman Spectrosc.

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The assignments of Raman bands in the spectra of silicate and germanate glasses, including SiO2, GeO2, Rb2Si4O9, NaFe3+Si3O8, anhydrous and hydrous albite (NaAlSi3O8) and anhydrous and deuterated Ge‐albite (NaAlGe3O8) and Ge‐jadeite (NaAlGe2O6), were re‐examined in the light of new information from Raman measurements at high pressures and temperatures. On the basis of polarized Raman spectra of single‐component (e.g. SiO2 and GeO2) glasses, it is demonstrated that the νas(T–O–T) mode (where T represents tetrahedrally coordinated cations, Si or Ge) gives rise to LO–TO splitting. The depolarized nature of the νas(T–O–T) LO–TO doublet in the Raman spectra of SiO2 and GeO2 glasses reflects the fact that the local site symmetry of T cations is close to Td. Persistence of the νas(T–O–T) LO–TO doublet slightly above the melting temperature demonstrates that significant intermediate range order exists even in the high‐temperature liquids. Likewise, in the spectra of NaFe3+Si3O8 and NaFe3+Si2O6 glasses, the high‐wavenumber νas(T–O–T) bands exhibit a depolarized character characteristic of a three‐dimensional network. The depolarized nature of the νas(T–O–T) bands indicates that the local site symmetry of the T cation is close to Td and that the triply degenerate (F) character of the νas(T–O–T) is preserved. Additionally, a significant shift in the position of the νas(T–O–T) mode on substituting NaFe3+ for Si4‐ reflects strong vibrational coupling of FeO4 and SiO4 tetrahedra in the glass. In the hydrated and deuterated aluminosilicate and ‐germanate glasses, it is proposed that the degeneracy of the νas(T–O–T) bands is lifted because of structural distortion caused by the presence of H3O+ (D3O+) ions. © 1997 John Wiley & Sons, Ltd.

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“…[9,13] Silica thermally treated above 400°C contains strained siloxanes, [17][18][19] which are present on the silica surface. [20][21][22][23] Si-O-Si bond angles in these dimer rings are 91.5°, whereas they are normally 151°for amorphous SiO 2 . [24] These strained defects act as strong acid-base sites, reacting rapidly, as indicated by the rapid uptake of water at low relative pressures in Figure 3.…”

Section: Full Papermentioning

confidence: 99%

Hydrothermally Robust Molecular Sieve Silica for Wet Gas Separation

Duke

Costa

Duong

et al. 2006

Adv Funct Materials

193

133

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A major challenge in silica membranes for gas separation is to maintain a robust pore structure in the presence of steam. In this work, use of a carbonized template is proposed to reduce damage to the pore structure by inhibiting silica migration along the membrane pore surface. This departs from the conventional wisdom of creating hydrophobic surfaces to achieve hydrostability. The carbonized‐template molecular sieve silica (CTMSS) membranes can then be applied to clean‐energy systems such as hydrogen separation and carbon dioxide sequestration, and membrane reactors where steam is present.

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Infrared spectra of edge-shared silicate tetrahedra

Cited by 117 publications

References 19 publications

Does Silica Surface Catalyse Peptide Bond Formation? New Insights from First‐Principles Calculations

Does Silica Surface Catalyse Peptide Bond Formation? New Insights from First‐Principles Calculations

Raman band assignments of silicate and germanate glasses using high-pressure and high-temperature spectral data

Hydrothermally Robust Molecular Sieve Silica for Wet Gas Separation

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