Synthesis and Characterisation of Photoresponsive Azobenzene-Biomolecule Conjugates

This thesis begins by overviewing the literature around the design, synthesis and application of molecular switches with a focus on the field of azobenzene switches, their isomerisation mechanisms and their value as control units on biological molecules. The introductory chapter is followed three synthesis chapters reporting on the application of copper promoted azide alkyne and uncatalysed nitrile oxide alkyne cycloadditions for conjugation of azobenzenes initially with small molecule test case substrates, followed by the synthesis of carbohydrate, peptide and nucleic acid conjugates. The preparation of range of monosaccaride, disaccharide and nucleoside azobenzene conjugates are detailed. The synthesis of a number of new azobenzenes bearing either 1,3-dipoles or their precursors, or dipolarophiles is described. Biomolecules bearing the complementary functionality are reported. The formation of isoxazole, triazole and ether linked biomolecule conjugates is demonstrated. Peptide conjugates have been prepared by cycloaddition in solution and on the solid phase. Formation of both mono- and divalent conjugates is demonstrated and a range of regioisomeric structures formed. All new compounds have been characterised by a variety of techniques including NMR spectroscopy, IR and UV/Vis spectroscopy, as well as HRMS. The structures of some compounds have been determined by x-ray crystal analysis. The photophysical properties of a selected range of bioconjugates has been explored: the photostationary states were determined using NMR spectroscopy and the kinetic parameters of the cis to trans relaxation process determined by a UV spectroscopy study. The experimental details are reported in chapter 7 and a full bibliography follows