Symmetric Functionalization of Polyhedral Phenylsilsesquioxanes as a Routeto Nano-Building Blocks.

[摘要] The design and synthesis of nanometer scale structures is of intense current interest.Herein we report on the ability to use symmetric, robust, mutable silsesquioxane([RSiO3/2]n) nano-building blocks to produce well-defined 3-D structures for electronic oradsorption applications. We are able to show the systematic effects of supermolecularcoordination to modulate the density of the molecular packing.This dissertation describes the synthesis of the elusivedecaphenylsilsesquioxane, and exploration of the substitutionally specific paraiodination of the octa-, deca- and dodeca-(p-iodophenyl)-silsesquioxanes, whose single crystalX-ray diffraction structures are reported. Octa(p-iodophenyl)-silsesquioxaneshows supermolecular coordination via Desiraju’s halogen-halogen short-contactsynthon, forming an open structure with a solvent accessible cavity comprising 40% ofthe unit cell.The application of palladium, nickel and copper catalyzed cross-couplingtechniques using the carbon-iodine bond is explored in order to divergently synthesizecrystalline derivatives. These derivatives include the octa(diphenylacetylene)silsesquioxane and the octa(hexaphenylbenzene)silsesquioxane (56 Aryl), whose single crystalX-ray diffraction structures are reported. We show that 56 Aryl, which containsmore carbon atoms than any other discrete molecule in the Cambridge StructuralDatabase, crystallizes into an extremely open structure with a solvent accessible cavitycomprising 55% of the volume. The supermolecular ordering driven by the bulkyhexaphenylbenzene moieties gives nanometer-scale channels along the ab plane.Substitutional specificity is explored in the bromination ofoctaphenylsilsesquioxane (OPS), and single-crystal X-ray diffraction structures arereported for the octa-, hexadeca- and tetraicosa-brominated derivatives. Precisesynthetic control is demonstrated by the unique catalyst-free bromination of OPS,providing the octa(o-bromophenyl)-silsesquioxane in low yield. An iron tribromidecatalyzed hexadeca-bromination gives the crystalline octa(2,5-dibromophenyl)-silsesquioxane in good yield, with a high density of 2.3 g/cc. Finally, the iron tribromidecatalyzedtetraicosa-bromination of OPS is described, producing a low yield of crystalswith a solid solution of substitution patterns coordinated by bromine-bromine shortcontacts.Lastly, Scholl-type dehydrogenative cyclization of theocta(hexaarylbenzene)silsesquioxane systems is explored by the addition of irontrichloride/nitromethane to a refluxing solution of the silsesquioxane in stannicchloride/dichloromethane. The products are analyzed by Proton Nuclear MagneticResonance Spectroscopy, Matrix Assisted Laser Desorption and Ionization – Time ofFlight Mass Spectroscopy and Diffuse Reflectance Fourier Transform Infra RedSpectroscopy.

[发布机构] University of Michigan

[效力级别] Chemistry

[关键词] Silsesquioxane;Chemistry;Science;Macromolecular Science & Engineering