Determination of a target molecule is of great importance both in industrial applications and human health. For a long time, this has attracted the extensive attention of researchers to develop new strategies. One of the vigorous sub-branches lies in supramolecular field. its ability to mimic a natural occurring event and unearth the mode of interaction for a targeted molecule. By varying the structure of a probe, researchers could rationally design synthetic sensors with selective binding affinity to target molecules and also satisfy different requirements for a certain application by combining different functional groups.The growing incidence of diabetes has promoted scientists to develop new effective strategies for early and quickly monitoring saccharide concentration. Interest in boronic acid-based saccharide probes has dramatically increased in the past several decades due to the unique properties of forming boronate esters with cis-diols. Previous work in James group demonstrated that by the introduction of a proximal amine group, the binding between boronic acid and saccharide can occur at neutral, i.e., physiological pH and the binding between boronic acids and saccharides can induce fluorescent "turn-on" responses.Acrylamide hydrogels with boron-additives have potential applications in separating saccharides and recognising glycation process in electrophoresis. Two monoboronic acid-based gel monomers 27 and 28 with different fluorophores have been synthesised and analysis measurements were carried out both in hydrogel, as well as in solution.As a Lewis acid, the strong binding affinity between boron and fluoride was also extensively explored to develop fluoride sensors. By investigating boron-containing 1,8-naphthalimide derivative 33, it is found that the binding between boron and fluoride could induce a red-shift of absorption (about 20 nm) with obvious colour changes and unique changes of NMR chemical shift. By comparison with control compounds (34 and 35), it was found that the addition of the boronic acid moiety would improve the selectivity, though at the expense of loss of sensitivity towards anions.Traditional molecular recognition is mainly based on host-guest interaction, where a synthetic host molecule could selectively interact with a guest molecule via weak and generally reversible interactions. The reaction-based sensing strategy is a new strategy in designing a high sensitivity probe toward a specific analyte, in which an irreversible reaction is normally utilised. Boronic acid moieties were extensively used both in exploring saccharide sensors and organic synthesis (Suzuki Homocoupling reaction). Here these two aspects were combined together to develop a Suzuki Homocoupling reaction-based saccharide sensing strategy. Different boronic acid substrates were employed and the sensing mechanism was investigated.Furthermore, as a collaboration project, colorimetric enantioselective recognition of chiral secondary alcohols was achieved via hydrogen bonding to a chiral metallocene containing chemosensor (38 and 39).The observed enantioselectivity of 38 could partly be due to the steric effect of the formed hydrogen bond complexes and the distance to the chiral centres.
|Date of Award||20 Jan 2014|
|Supervisor||Tony James (Supervisor)|