Design, Synthesis And Properties Of Functional Silanes With AIEE Effect

Owing to the intermolecular interactions and the corresponding nonradiative decay, the fluorescence efficiency of organic luminescent materials often decreases in the solid state. This aggregation-caused emission quenching (ACQ) has seriously obstructed advancement in the development of efficient organic light-emitting diodes (OLEDs), chemosensors, biosensors, etc. To overcome this problem, considerable research has focused on the synthesis of compounds possessing aggregation-induced emission (AIE) or aggregation-induced emission enhancement (AIEE) properties. These solid-state, highly emissive organic materials are regarded as competitive candidates for practical use as highly emissive materials, and seem especially ideal for OLEDs. Functionalized silanes are defined as the small organosilicon compounds with functional groups, and compared to conventional carbon compounds, they have many advantages, such as more accessible synthesis, high thermal stability and high color purity. Thus they have been applied in extensive areas, including organic light emitting devices, chemical sensors or biosensors and so on. In this dissertation, investigations have been carried out and focused on the design, synthesis, AIEE properties and application of cyano functionalized silanes. The main contents are as follows:1. Two kinds of phenylethynyl-bridged cyano functionalized silanes, namely, bis(4-cyanophenylethynyl)dimethylsilane (CN-1) and bis(4-cyanophenylethynyl)diphenylsilane (CN-2), have been synthesized and characterized by FTIR, NMR, elementary analysis, HRMS and XRD, which provides a method to introduce cyano group into functionalized silanes. To investigate the AIEE property, the fluorescent behaviors, UV-vis absorption spectra and SEM were measured in the mixture solution of water/THF. By comparison with4-((trimethylsilyl)ethynyl)benzonitrile (1) and4-ethynybenzonitrile (2),4-cyanophenylethynyl unit is found to be the structure base to induce the AIEE phenomenon and the silicon core may enhance the AIEE effect. By crystal structure analysis and theoretical calculation, the AIEE mechanism was tried to obtain. Moreover, both CN-1and CN-2showed the obvious quenching response for2,4,6-trinitrotoluene (TNT) in THF solution, indicating their practical application in explosive detection for TNT.2. To broden the AIE/AIEE compounds, a series of diphenyl-bridged cyano functionalized silanes, namely, bis(4-cyanodiphenyl)dimethylsilane (2me), bis(4-cyanodiphenyl)diphenylsilane (2ph), tri(4-cyanodiphenyl)methylsilane (3me), tri(4-cyanodiphenyl)phenylsilane(3ph) and tetra(4-cyanodiphenyl)silane (4ph) have been synthesized by Suzuki coupling reaction using bromophenyl silanes as the starting materials. These compounds were well characterized by FTIR, NMR, elementary analysis and HRMS, and the thermal stability was measured by TGA and DSC. The optical analysis shows that these cyano functionalized silanes have unique AIEE property. These compounds are fluorescent with emission in the region of violet to blue, and possess large HOMO-LUMO energy gaps ranging from4.7377eV to4.7481eV. Thus they could be potentially used as blue emitters or hole blocking materials in OLEDs. Furthermore, these compounds all showed the obvious fluorescence quenching and ultraviolet (UV) absorption enhancement response for diphenylamine (DPA) in dicholomethane solution, indicating their potentially practical application in DPA detection.