Synthesis and analysis of siloranes for use as a biomaterial and extended twisted molecular ribbons

Abstract

The development of complex organic molecules with industrial potential requires meticulous synthetic methodologies coupled with detailed investigations surrounding their physical properties. This dissertation encompasses the study of two such projects: (i) the synthesis, optimization, and quality control of siloranes for use as a biomaterial (i.e., bone cements) and (ii) the investigation of the synthesis, physical properties, and barrier to enantiomerization of twisted molecular ribbons. Optimization of the synthesis of the silorane monomers PHEPSI and CYGEP was completed via metal-catalyzed hydrosilylation. PHEPSI was synthesized utilizing a monomeric version of the rhodium-based Wilkinson’s catalyst. The synthesis of CYGEP was accomplished using two versions of the platinum-based Lamoreaux’s catalyst (in-house versus commercial). In both cases, formation of CYGEP was accomplished only in those reactions in which acetonitrile was present, otherwise polymerization occurred. A quality control investigation found that for use of these monomers as a potential biomaterial, a high grade of Wilkinson’s catalyst must be utilized for the synthesis of PHEPSI, while use of the commercial catalyst is sufficient for the synthesis of CYGEP. Mixing of the monomers no more than one month post purification prevents the decomposition of PHEPSI. An exploration into the effect of end caps and substitution of the acene skeleton was completed. The synthesis of the target pentacene and anthracene compounds was focused on the incorporation of isopropyl substituents while extension of the acene skeleton was expanded to the hexacene diol. The targets were synthesized utilizing a series of Diels-Alder and reduction reactions. The incorporation of the isopropyl substituent was accomplished through the use of lithium reagents generated in situ. The barrier to enantiomerization was then studied on the aromatized isopropyl acenes utilizing VT-NMR spectroscopy. Coalescence of the methyl peaks in the 1H NMR spectrum was not observed at temperatures up to 408 K. Utilizing this method, the barrier to enantiomerization of these compounds was found to be greater than 24.0 kcal/mol. The stages of the synthesis were determined through mass spectrometry, 1H and 13C NMR spectroscopy, and in some cases X-ray crystallography. Fluorescence of the isopropyl targets was investigated through UV-Vis spectroscopy