Development of conjugated boronate ester-linked materials for optical sensing applications targeting small molecules

摘要

Conjugated boronate ester-linked materials were delveloped for optical sensing applications, targeting small analytes. Backgrounds and significants for conjugated boron containing materials and their applications in molecular sensing were introduced in chapter 1. The development of cross-reactive sensors and sensor arrays was mainly discussed. Multi-dimensional response analysis assited by statistical techneques was also illustrated in this chapter to demonstrate its capability in differentiation multiple analytes. In chapter 2, a series of conjugated bis(dioxaborole)s (boronate esters) were synthesized to understand how structural modifications influence the electronic properties of these esters. Spectroscopic observations and computational studies of these compounds suggested that both the central aromatic components and substituents on the terminal diols can affect the electronic properties. The extension of pi-conjugation through the vacant p orbitals on boron atoms enables the boronate esters to serve as optical sensors towards Lewis base substrates, because the Lewis acid-base interaction causes the change in hybridization of boron, thus interrupting effective conjugation. In chapter 3, thiophene containing conjugated boronate esters were used to study the factors affecting the binding interactions between boronate esters and low molecular weight volatile amines. Lewis acidity and steric accessibility of the boron binding sites were significantly impacted by altering substituents on the diol portion of the boronate esters, which results in different, unique and reproducible responses towards different amine analytes with varied structures and basicity. The binding mechanism was studied using single crystal X-ray diffraction, 1H NMR, as well as binding affinities obtained by absorption titrations. In chapter 4, a cross-reactive sensor array based on these thiophene containing boronate esters was used to differentiate low molecular weight aliphatic amines. Multiple wavelengths from the absorption spectrum for each diester host responding to a particular amine were used to create a unique pattern for the analyte. Statistics analysis was applied to differentiate the analytes with high classification accuracy (>99%). An alternative approach towards aliphatic diamine detection was also investigated using a side-chain functionalized poly(thiophene) which was immobilized on a solid support in Chapter 5. Several strategies were used to immobilize polymers on the solid supports, towards the development of portable sensors. Computational studies to further understand the influence of substituted positions on the Lewis acidity of boronate esters were included in Chapter 6. To confirm the validity of the caluculations, the approaches to get experimental results were planned as future work. Additionally, more core aromatic components and substituents were porposed to modify the strucutres, as well as to make poly(boronate ester)s, thus leading to more effective conjugations. Immobilized poly(boronate ester) sensor was designed towards detecting amine in vapor phase.