Polyhedral Phenylsilsesquioxanes

Laine, Richard M.; Roll, Mark F.

doi:10.1021/ma102360t

Cited by 245 publications

(190 citation statements)

References 145 publications

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“…Clearly some zeolite topologies containing D4R units require fluoride addition in synthesis (39). The earlier papers of George and Catlow (12,13), Hagelberg and coworkers (14), Tossell (15), and Laine and Roll (16), and our analysis show the magnitude and nature of the bonding. Fluoride acting as a template is similar to that of a stabilizing ligand, providing net stabilization of more than 80 kcal/mol for a single D4R unit, as calculated here.…”

Section: Discussionsupporting

confidence: 51%

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Eight-coordinate fluoride in a silicate double-four-ring

Goesten

Hoffmann

Bickelhaupt

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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Fluoride, nature's smallest anion, is capable of covalently coordinating to eight silicon atoms. The setting is a simple and common motif in zeolite chemistry: the box-shaped silicate double-four-ring (D4R). Fluoride seeks its center. It is the strain of box deformation that keeps fluoride in the middle of the box, and freezes what would be a transition state in its absence. Hypervalent bonding ensues. Fluoride's compactness works to its advantage in stabilizing the cage; chloride, bromide, and iodide do not bring about stabilization due to greater steric repulsion with the box frame. The combination of strain and hypervalent bonding, and the way they work in concert to yield this unusual case of multiple hypervalence, has potential for extension to a broader range of solidstate compounds.hat is the maximum number of atoms to which a maingroup element may bond? Four, one would normally think. But, hypervalence and delocalized bonding enlarge the upper range--no one bats an eyelid at silicon binding 6 ligands, and there exist cases of arguably 10-coordinate Si (1, 2). Much thinking on high coordination focuses on atomic or ionic radii, and packing considerations. Or, one can approach the problem from a quantum-chemical perspective. In this paper, we follow the latter course, and operate at the crossing point between molecular and extended systems. We explore how the upper bound for coordination number is determined by attractive and repulsive forces, adding in a factor of strain, associated with deforming a molecular cage that entraps an element in its center.The stage for this work is set by a simple and common motif in catalysis and separation: the silicate double-four-ring (D4R), one of the archetypal building blocks in large-pore zeolites. By use of relativistic density-functional theory (DFT) calculations and Kohn-Sham molecular orbital theory (3-6), we will see that within this box-like environment, fluoride coordinates, actually binds, to eight silicon atoms.

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Section: Discussionsupporting

confidence: 51%

“…There are other low-lying σ*-orbitals, even a t 1u set matching the symmetry of the F [2p], but not in providing good overlap; only the indicated a 1g and t 1u levels do this (parenthetically, the antibonding a 1g combination turns out to be the unusual, cagecentered LUMO that Laine and Roll calculated, mentioned above) (16).…”

Section: Discussionmentioning

confidence: 99%

Eight-coordinate fluoride in a silicate double-four-ring

Goesten

Hoffmann

Bickelhaupt

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…The interest in this family of compounds has generated 14 review articles covering many ways on the synthesis, chemistry and properties of silsesquioxanes (Laine & Roll, 2011;Cordes, Lickiss, & Rataboul, 2010). However a recent literature search did not find any reports on the chemical modification of silsesquioxanes and their application to the molecules under study in this article, employing or not the proposed methodology.…”

Section: Introductionmentioning

confidence: 99%

“…Silsesquioxanes are materials with an empirical formula (RSiO 1.5 )n, where R is a hydrogen atom or an organic group (Do Carmo, Bicalho, Silveira, Dias Filho, & Paim, 2013;Cordes, Lickiss, & Rataboul, 2010;Baney, Itoh, Sakakibara, & Suzukit, 1995;Kuo & Chang, 2011;Xu, Loo, & Wang, 2011;Tanaka & Chujo, 2012;Li-Chih & Shea, 2011) and n = 4, 6, 8, 10 (n ≥ 4) (Cordes, Lickiss, & Rataboul, 2010). Due to their intrinsic quality properties, and as a consequence in recent years there has been a large increase in the number of patents and publications related to these materials (Laine & Roll, 2011;Cordes, Lickiss, & Rataboul, 2010).…”

Section: Introductionmentioning

confidence: 99%

Synthesis, Characterization and Thermal Properties of Silsesquioxane Organically Modified With 4,5-Diphenyl-2-Imidazolethiol

Carmo

Magossi²,

Bicalho³

et al. 2014

IJC

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The present paper describes the preparation of a nanostructured silsesquioxane, the octa-(3-chloropropyl)-octasilsesquioxane (S) that was organofunctionalised with the 4,5-Diphenyl-2-imidazolethiol (DIT). The modification of silsesquioxane with DIT proposed in this paper follows two steps. The composite prepared after functionalization was ascribed as SDIT. The composite SDIT and precursors were characterized by infrared (FTIR), 13 C and 29 Si Nuclear Resonance Magnetic (NMR) in solid state, Scanning Electron microscopy (SEM); X-Ray Diffraction (XRD); Energy-Dispersive X-ray spectroscopy (EDS) and Thermogravimetry. By spectroscopic analysis using above techniques, we conclude with that the SDIT synthesis was conducted with success. It was observed a cluster of particles containing cavities in an orderly fashion. The themogravimetry analyzes performed in two different atmospheres, concluding that the materials (S, DIT and SDIT) when in air atmosphere has a slower degradation process in relation to nitrogen atmosphere. The thermogravimetry of SDIT indicate a greater thermal stability in nitrogen atmosphere.

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“…Silsesquioxanes have a large number of applications, such as catalysts (Gnanasekaran et al, 2009;Kuo, & Chang, 2011;Li et al, 2001;Provatas et al, 1998;Laine & Roll, 2011), liquid crystals (Gnanasekaran et al, 2009;Cordes et al, 2010), biosensors (Cordes et al, 2010;Kuo & Chang, 2011;Xu et al, 2011) and silica interface (Handke & Kowalewska, 2011) and dendrimer precursors . It is very interesting to know that their properties increase when these structures are functionalized with organic groups forming hybrid materials (Gnanasekaran et al, 2009;Xu et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Use of a Silsesquioxane Organically Modified with 4-amino-5-(4-pyridyl)-4H-1,2,4-triazole-3-thiol (APTT) for Adsorption of Metal Ions

Soares¹,

Silveira²,

Silvestrini³

et al. 2013

IJC

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This paper describes the preparation of a nanostructured silsesquioxane, the cloropropilsilsesquioxano (S) that was organofunctionalised with the 4-amino-5-4(pyridyl)-4H-1,2,4-triazole-3-thiol (APTT), the material obtained of the functionalization was described as SA. The material SA was characterized by spectroscopy in the region of infrared (FTIR). After proper characterization, were carried studies on adsorption of metallic ions such as Cu 2+ , Ni 2+ and Cd 2+ in the active sites of SA. Different methods were studied in the adsorption of metal ions above: aqueous, ethanol 42% and ethanol 99%, determining the adsorption equilibrium time, which for both means and metals the maximum time averaged 35 minutes. After determining the adsorption equilibrium time of metal ions in each system, we determined the specific sorption capacity (Nf max ) through adsorption isotherms. The results suggest that the sorption of metal ions on DPPIPS occurs mainly by surface complexation and a Langmuir model allowed describing the sorption of the metal ions on SA. The excellent adsorptive capacity made possible the development of a method for determination of metal ions at trace level in real samples such as waste water, ethanol fuel and alcoholics beverages.

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Polyhedral Phenylsilsesquioxanes

Cited by 245 publications

References 145 publications

Eight-coordinate fluoride in a silicate double-four-ring

Eight-coordinate fluoride in a silicate double-four-ring

Synthesis, Characterization and Thermal Properties of Silsesquioxane Organically Modified With 4,5-Diphenyl-2-Imidazolethiol

Use of a Silsesquioxane Organically Modified with 4-amino-5-(4-pyridyl)-4H-1,2,4-triazole-3-thiol (APTT) for Adsorption of Metal Ions

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