Part I: The synthesis of chenodeoxycholic acid derived macrocyles and cage compounds. Part II. Sonogashira coupling for the synthesis of well-defined π-conjugated arylene ethynylene oligomers as blue-light-emitting materials

Abstract

The design and development of novel chenodeoxychoic acid (CDCA) derivatives and its molecular architecture was accomplished. A novel CDCA derivative with an ambient CO2 insertion to 7α-side chain has been serendipitously discovered. It is the first time that CO2 has been directly introduced to the steroid molecules by organic synthetic method. It also provides a potential methodology to synthesize 14C labeled bile acid derivatives to explore the transport mechanism of hASBT. Secondly, a series of CDCA based macrocycles with inner cavities have been synthesized and characterized. Particularly, the single crystal X-ray analysis has revealed an unequivocal structure of 4-pentenoate functionalized cyclodimer (K). The first CDCA based cage-type molecular architecture has been achieved by Grubb's reaction. Especially we have successfully synthesized and separated the first cis/trans isomers of the bridged CDCA cyclodimer. The most exciting thing is we have discovered the structure of cis bridged cyclodimer by X-ray crystallography. The cavity size for cis-cyclodimer is about 1 nm x 1 nm x 0.6 nm dimension. The briged cyclodimer with well-defined small inner cavity could be used for gas adsorption such as hydrogen storage container. In addition, the cis/trans isomers of double handle basket-shaped cyclotetramer O could be used for drug delivery. Its inner cavity is suitable for encapsulating hydrophobic drug molecules. In part II, it involved in the synthesis and characterization of well-defined π-conjugated arylene ethynylene oligomers. These oligomers have applications in the fabrication of potential organic photovoltaic cells and organic light-emitting diodes (OLEDs). Four series of arylene ethynylene oligomers: mono-terminated di-tert-butyl-substituted OPEs 4a-7a, mono-terminated tert-butyl substituted mono-iodo-substituted OPEs 8-11, unsymmetric phenylene-ethynylene trimers and tetramers 13a-d, 16a-d and unsymmetrical phenylene-ethynylene compounds with the terminal allyloxy group 18a-f, 19a-b and 23 have been successfully synthesized using oxygen-free Sonogashira reaction conditions. The structures of these oligomers have been confirmed by 1H and 13C NMR spectroscopy, HR-MS, MALDI-TOF spectroscopy. The detailed structure of oligomers 5a, 5b and homo4 were revealed by single X-ray crystal diffraction measurements. The electronic properties of these oligomers have been studied by UV-vis and fluorescence luminescence spectroscopy. It has been observed that both UV absorption and FL emission maxima have red shifts with either increasing conjugation length of oligomers or with more conjugated chromophores. The quantum yields of these oligomers are ranged from 0.2 to 1.0. In addition, the quantum yield for 5b,6a, 7a, trimers 13a-d, and tetramers 16a-d are close to 1 which means these oligomers has very high emission efficiency.