Synthesis, Properties And Applications Of Stimuli-Responsive Heterocyclic Nitrogen Compounds

Stimuli-responsive materials are a type of novel materials that can change their physical or chemical properties under environmental stimulation. Environmental stimulation factors included mechanical pressure, acid/base, metal ion, temperature, and electromagnetism and so on, the kind of smart materials have received considerable studied because of their necessary realistic significances and extensive application prospect in information record, data storage, anti-counterfeiting of brands and optoelectronic devices. Stimuli-responsive organic optical functional materials can be able to sense the environment change and achieve color change. Among them, heterocyclic nitrogen derivatives can achieve stimuli-responsive properties easily, due to their facile modified structure, multiple coordination modes, and so forth. According to international research progress of stimuli-responsive materials, basing on structure-property relationships, we have synthesized a series of heterocyclic nitrogen derivatives in this dissertation, and studied the photophysical properties and stimuli-responsive properties. The main research contents are listed as follows:1. We gained three tetraphenyl imidazole derivatives functionalized by an a-cyanostilbene unit (L1, L2 and L3) were synthesized via Debus-Radziszewski and Knoevenagel reaction. The photophysical properties in different polar solvents and density functional theory (DFT) indicated that the compounds showed a typical intramolecular charge transfer (ICT) effect; and the UV-vis spectra and fluorescence spectra confirmed that the compounds exhibited obviously aggregation-induced emission enhancement (AIEE) property. The compounds showed obvious red-shifted of fluorescence emission after grinding, and exhibited mechanofluorochromic properties. The powder X-ray diffraction and crystalline structures indicated that the destruction of the crystalline structure leads to the planarization of molecular conformation and the increase of the conjugation degree, and the red-shift of fluorescence emission after grinding.2. Basing on the investigations of above experiment, we gained two AIEE properties imidazole derivatives (L4 and L5) with ICT effect, and were characteristiced by FT-IR, H NMR and C NMR, and gained crystal of L4 and analyzed the crystal structure. The fluorescence emission peaks of compounds L4 and L5 showed obvious red-shifted under the trifluoroacetic acid (TFA) vapor condition, and can be recovered when treated with triethylamine (TEA) vapor. The results indicated that the acid/base showed reversible stimuli-responsive properties for compounds L4 and L5, and can be implemented to acid/base switch.3. A pyridinyl group compound (L6) containing organboron unit with ICT effect was designed and synthesized via condensation reaction and reduction reaction. The compound L6 exhibited high fluorescence quantum yields both in organic solvents (yield quantum:0.50) and solid state (yield quantum:0.39). Our investigations showed that the mercury ion can stimulate the fluorescence peak of compound L6 occur red-shifted (change from cyan to yellow-green), and can be an excellent fluorescent sensor of Hg2+ with high selectivity in solution and the detection limit was 5.0×10-8 M. In solid state, the compound L6 can change fluorescence emission from yellow to red under the TFA vapor condition, and can be recovered from red to yellow emissive when treated with TEA vapor. The 1H NMR spectra experiments indicated that the combination of pyridine unit with mercury ion or proton can increase the intramolecular charge transfer effect, and caused the red-shifted of fluorescence emission peak. Compound L6 processed dual functions as mercury ion chemosensor and acid/base stimulated switching.