Spirocyclic silicon alkoxides were synthesized by reaction of Si(OMe)4 with derivatives of salicylic alcohol and studied by in situ differential scanning calorimetry with regard to twin polymerization (TP). Both, thermally induced and proton‐assisted TP gave nanostructured hybrid materials composed of a phenolic resin and silica. Carbonization and subsequent treatment with HF(aq) resulted in microporous carbon, whereas oxidation in air provided mesoporous silica. DFT calculations were performed to obtain a more detailed insight into the first reaction steps of proton‐assisted TP and to support the hypothesis of a reactivity scale based on steric and electronic features of the silicon‐containing precursors (twin monomers). The calculated reaction barriers for the initial reaction steps of proton‐assisted TP are qualitatively in accordance with the Hammett constants of the substituents at the salicylate moiety. This result offers a simple method to predict the reactivity for twin monomers.
The dispersion type Bi···π arene interaction is one of the important structural features in the assembly process of arylbismuth compounds. Several triarylbismuth compounds and polymorphs are discussed and compared based on the analysis of single crystal X-ray diffraction data and computational studies. First, the crystal structures of polymorphs of Ph3Bi (1) are described emphasizing on the description of London dispersion type bismuth···π arene interactions and other van der Waals interactions in the solid state and the effect of it on polymorphism. For comparison we have chosen the substituted arylbismuth compounds (C6H4-CH═CH2-4)3Bi (2), (C6H4-OMe-4)3Bi (3), (C6H3-t-Bu2-3,5)3Bi (4) and (C6H3-t-Bu2-3,5)2BiCl (5). The structural analyses revealed that only two of them show London dispersion type bismuth···π arene interactions. One of them is the styryl derivative 2, for which two polymorphs were isolated. Polymorph 2a crystallizes in the orthorhombic space group P212121, while polymorph 2b exhibits the monoclinic space group P21/c. The general structure of 2a is similar to the monoclinic C2/c modification of Ph3Bi (1a), which leads to the formation of zig-zag Bi–arenecentroid ribbons formed as a result of bismuth···π arene interactions and π···π intermolecular contacts. In the crystal structures of the polymorph 2b as well as for 4 bismuth···π arene interactions are not observed, but both compounds revealed C–HPh···π intermolecular contacts, as likewise observed in all of the three described polymorphs of Ph3Bi. For compound 3 intermolecular contacts as a result of coordination of the methoxy group to neighboring bismuth atoms are observed overruling Bi···π arene contacts. Compound 5 shows a combination of donor acceptor Bi···Cl and Bi···π arene interactions, resulting in an intermolecular pincer-type coordination at the bismuth atom. A detailed analysis of three polymorphs of Ph3Bi (1), which were chosen as model systems, at the DFT-D level of theory supported by DLPNO-CCSD(T) calculations reveals how van der Waals interactions between different structural features balance in order to stabilize molecular arrangements present in the crystal structure. Furthermore, the computational results allow to group this class of compounds into the range of heavy main group element compounds which have been characterized as dispersion energy donors in previous work.
The surfactant-free synthesis of β-phase germanium dioxide nanoparticles in ortho-methoxy benzyl alcohol and benzyl alcohol has been reported. Characterisation of the hexagonal β-GeO 2 crystals, which involves powder X-ray diffraction, nitrogen adsorption measurements (Brunauer-Emmett-Teller method), dynamic light scattering measurements, IR spectroscopy, transmission electron microscopy and energy-dispersive X-ray analysis has been presented. Synthesis of β-GeO 2 under ambient conditions in benzyl alcohol results in nanoparticles with diameters below 20 nm, whereas the synthesis under inert conditions in benzyl alcohol at reflux (205°C) gives larger nanoparticles. In ortho-methoxy benzyl alcohol, agglomerates with particle sizes above 100 nm are observed under inert atmosphere conditions at room temperature.
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