Characterization of NMR, IR, and Raman spectra for siloxanes and silsesquioxanes: a mini review

Sato, Yohei; Hayami, Ryohei; Gunji, Takahiro

doi:10.1007/s10971-022-05920-y

Cited by 38 publications

(32 citation statements)

References 195 publications

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“…The T 14 Ph 14 silsesquioxane 2 gives rise to three signals in the 29 Si NMR at À 76.2, À 77.6 and À 79.1 ppm in C 6 D 6 as depicted in Figure 3, which is in the usual range of phenyl-substituted silsesquioxanes. [18] Compared to the Ph 7 T 7 (OH) 3 starting material (À 68.3, À 76.9 and À 77.8 ppm) the chemical shifts of 2 are closer together due to the very similar coordination environment at each silicon center. A 1 HÀ 29 Si correlation NMR experiment in CDCl 3 (Figure S8) indicates the signal at À 76.9 ppm to represent the two silicon atoms located on the C 3 rotation axis in the T 7 fragments (Si28 and Si15 atoms in Figure 2), by assignment of the corresponding 1 H NMR resonances to the meta hydrogen atoms of the phenyl groups based on the relative intensities (see Figures S1 and S2).…”

Section: Resultsmentioning

confidence: 95%

“…In our case, it is not surprising that the different silicon environments cannot be resolved in the solid state given the 42 silicon atoms of the three crystallographically inequivalent T 14 Ph 14 molecules with only slightly different chemical environments. Diagnostically, the IR spectrum in Figure S10 of silsesquioxane 2 (ATR) lacks the distinct OH bands of the T 7 Ph 7 (OH) 3 precursor (ν OH = 3234 cm À 1 , ν SiOH = 885 cm À 1 , Figure S9) [18] but is otherwise almost identical. Thermogravimetric analysis and differential scanning calorimetry of the T 14 Ph 14 isomer show a behavior similar to that of the T 8 Ph 8 to T 12 Ph 12 systems (see Supporting Information for details).…”

Section: Resultsmentioning

confidence: 99%

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Polyhedral Oligomeric Silsesquioxane D_3h‐(RSiO_1.5)₁₄

Hunsicker,

Ankur,

Morgenstern

et al. 2024

Chemistry A European J

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While smaller polyhedral oligomeric silsesquioxanes TnRn (POSS) are readily accessible or even commercially available, unambiguously authenticated larger systems (n > 12) have barely been reported. Synthesis and isolation procedures are lengthy, and yields are often very low. Herein, we present the surprisingly straightforward and high‐yielding access to the phenyl‐substituted derivative of a so far only postulated second D3h‐symmetric T14 isomer and with that the largest crystallographically characterized POSS cage with organic substituents. Treatment of the commercially available incompletely condensed T7Ph7(OH)3 silsesquioxane with catalytic amounts of trifluoromethanesulfonic acid results in high yields of the T14Ph14 framework, which is isolated in crystalline form by a simple work‐up. D3h‐T14Ph14 was analyzed by single crystal X‐ray diffraction, multinuclear NMR spectroscopy and thermal analysis. The relative energies of all four theoretically possible T14Ph14 isomers were determined by optimization of the corresponding structure using DFT methods.

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Section: Resultsmentioning

confidence: 95%

Section: Resultsmentioning

confidence: 99%

Polyhedral Oligomeric Silsesquioxane D_3h‐(RSiO_1.5)₁₄

Hunsicker,

Ankur,

Morgenstern

et al. 2024

Chemistry A European J

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“…Progression of trimethylsilylation was con rmed by FTIR (Figure S2), by the appearance of the adsorption bands corresponding to δSi-Me (approximately 1250 cm − 1 ) and ρSi-Me (approximately 840 cm − 1 ), and the no appearance of the band corresponding to υSi-OH (approximately 950 cm − 1 ) [34,40,41]. No υSi-O-Si adsorption band was observed at 1200-1100 or 1040-1000 cm − 1 ; hence, the main structures of ethoxysilane-TMSs could be attributed to their linear, branched, and cyclic forms [34,42].…”

Section: Hydrolysis Of Teos Heds and Oetsmentioning

confidence: 92%

Hydrolysis and condensation behavior of tetraethoxysilane, hexaethoxydisiloxane, and octaethoxytrisiloxane

Sato

Sugimoto

Iwashina

et al. 2023

Preprint

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In the initial stage of the hydrolysis–condensation of tetraethoxysilane (TEOS), hexaethoxydisiloxane (HEDS) and octaethoxytrisiloxane (OETS) are formed. However, little is known about the hydrolysis–condensation of HEDS and OETS. In this study, the hydrolysis–condensation of TEOS, HEDS, and OETS was investigated. HEDS and OETS were synthesized from diethoxy(diisocyanato)silane, a raw material with controllable functionality. The hydrolysis of TEOS, HEDS, and OETS was analyzed by mass spectroscopy, gel permeation chromatography, and nuclear magnetic resonance. The hydrolysis–condensation product of TEOS was a three-dimensional network-type polysiloxane. The hydrolysis–condensationproduct of HEDS consisted mainly of four-membered cyclic siloxane. The hydrolysis–condensation product of OETS consisted mainly of various membered cyclic siloxanes.

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“…The chemical shift of siloxane, particularly cyclosiloxanes on 29 Si NMR reflects their structural information. 17 The 29 Si NMR of cyclosiloxanes 2 and 3 gave a singlet peak at −29.4 and −37.0 ppm, respectively. The 29 Si NMR signals for analogous hexaphenylcyclotrisiloxane 18 and octaphenylcyclotetrasiloxane 19 were observed at −37.0 and −42.8 ppm, respectively, indicating that the 29 Si NMR signals of 2 and 3 are slightly downfield shifted compared with the corresponding phenyl analogues, which may due to the larger ring current of the pyrenyl groups.…”

Section: Introductionmentioning

confidence: 97%

“…The chemical shift of siloxane, particularly cyclosiloxanes on 29 Si NMR reflects their structural information . The 29 Si NMR of cyclosiloxanes 2 and 3 gave a singlet peak at −29.4 and −37.0 ppm, respectively.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and Characterization of Cyclotri- and Tetrasiloxanes with Pyrenyl Groups

et al. 2022

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Cyclosiloxanes directly bearing polyaromatic groups on silicon atoms have scarcely been reported. Herein, hexa(1pyrenyl)cyclotrisiloxane (2) and octa(1-pyrenyl)cyclotetrasiloxane (3) were successfully prepared from di(1-pyrenyl)silanediol (1) in the presence of a weak base such as tetraethylammonium acetate and triethylamine in MeCN. The structure of the cyclosiloxanes bearing multiple pyrenyl groups in the solid and solution states was evaluated by NMR, X-ray crystallography, and density functional theory (DFT) calculations. All pyrenyl groups of 2 were oriented outward, and no π−π stacking of adjacent pyrenyl groups was observed. However, all pairs of adjacent pyrenyl groups at 1-and 3-positions in 3 are oriented in the same direction and were π−π stacked with respect to each other. The UV−vis spectra of 2 and 3 in organic solvents showed a slight broadening of the peaks, as observed for typical pyrene derivatives. Interestingly, the fluorescence spectra of 2 showed small monomer and strong excimer emissions; however, those of 3 showed only a strong excimer emission in all solvents. Partially pyrenylated cyclotri-and tetrasiloxanes (compounds 4 and 5) showed solvent-dependent monomer and excimer spectra as observed for di(1-pyrenyl)silane derivatives, implying that the excimer emissions of 2 and 3 arise from mainly geminal and vicinal pyrenyl groups, respectively.

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Characterization of NMR, IR, and Raman spectra for siloxanes and silsesquioxanes: a mini review

Cited by 38 publications

References 195 publications

Polyhedral Oligomeric Silsesquioxane D_3h‐(RSiO_1.5)₁₄

Polyhedral Oligomeric Silsesquioxane D_3h‐(RSiO_1.5)₁₄

Hydrolysis and condensation behavior of tetraethoxysilane, hexaethoxydisiloxane, and octaethoxytrisiloxane

Synthesis and Characterization of Cyclotri- and Tetrasiloxanes with Pyrenyl Groups

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Characterization of NMR, IR, and Raman spectra for siloxanes and silsesquioxanes: a mini review

Cited by 38 publications

References 195 publications

Polyhedral Oligomeric Silsesquioxane D3h‐(RSiO1.5)14

Polyhedral Oligomeric Silsesquioxane D3h‐(RSiO1.5)14

Hydrolysis and condensation behavior of tetraethoxysilane, hexaethoxydisiloxane, and octaethoxytrisiloxane

Synthesis and Characterization of Cyclotri- and Tetrasiloxanes with Pyrenyl Groups

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Polyhedral Oligomeric Silsesquioxane D_3h‐(RSiO_1.5)₁₄

Polyhedral Oligomeric Silsesquioxane D_3h‐(RSiO_1.5)₁₄