Synthesis, Nanoscale Self-assembly And Optical Properties Of Triphenylamine And Carbazole Derivatives

Functional organic nanomaterial is one of the most important branches in the field of nanoscience and technology. Organic molecules with functional diversity and structure tailorability can flexibly self-assemble in the nanoscale and regulate the molecules properties, which have good potential applications in catalysis, bioimaging, drug delivery, chemical sensing and organic optoelectronic materials etc. The self-assembly process of organic materials can be easily affected by the internal factors such as molecular geometry, dipole-dipole interaction, hydrogen bond,π-π stacking interaction etc, and the external factors such as solvent, acid-base environment, metal ions etc, which can directly influence the nanostructure and properties. At the same time, the organic molecules with aggregation induced emission properties (AIE) have received increasing interest in recent years. To design and synthesize novel compounds with AIE properties and study its structure-activity relationship between structure and photophysical properties have important theoretical and practical value for the further development in the field of AIE. The main contents are as follows:(1) Triphenylamine has good electron donating ability, hole transport properties and excellent photoelectric properties, which can achieve functionalization by structural modification; carboxyl group is a kind of electron acceptor with good electron withdrawing ability. By coupling the triphenylamine and carboxyl group through conjugated bridge, it can form the intramolecular charge transfer (ICT) molecule with D-π-A (D= doner, A= acceptor) structure. Three triphenylamine carboxylic acid derivatives L1-L3 with D-n-A structure were designed and synthesized, their structures were characterized detailedly by FT-IR,1H-NMR and 13C-NMR. The crystal structures of L1 and L2 were determined and shown that there were strong intermolecular weak interaction of hydrogen bond, C-H…π and π-π interaction, which play a leading role in the self-assembly process on the nanoscale.(2) The organic nanostructures of L1-L3 were prepared by reprecipitation method. The carboxyl group in molecule could be protonated and deprotonated by changing the solution acid-base environment, which could change intermolecular interactions, influence the process of the self-assembly and further regulate the optical properties. The results shown that the molecule accumulated to form three-dimensional structure by hydrogen bond, C-H…π and π-π stacking interaction in acidic environment; The hydrogen bonding interactions gradually weaken or even disappear due to deprotonation in alkaline environment, the molecule accumulated to form two-dimensional structure. Based on the Hard-Soft-Acid-Base theory, when rare earth metal ions were added to preparation process, the intermolecular interactions between metal ions and the carboxyl groups could be changed, and induced to form multiple nanostructures. The results shown further that different nanostructures possessed of different optical properties, it could realize the optimization of the optical properties through the regulation of nanostructures.(3) A series of carbazole derivatives L4-L7 were designed and synthesized, all the compounds possessed of aggregation induced emission properties. By introducing double cyano group in the L4 and L5 molecule, there existed quite strong intermolecular interactions of C-N…H. The intermolecular interactions helped rigidify the conformation and physical restriction of intramolecular rotation in the aggregate states, which caused the fluorescence enhancement. In addition, the carbazole group connected to another benzimidazole ring in L4 molecule by methylene, making molecular structure more distorted, effectively avoided the π-π stacking interactions. As a result, L4 exhibited more excellent aggregation induced luminescence properties than L5, and the maximum fluorescence intensity of L4 was 3.6 times of L5 under the same conditions. When nitro substituted phenylacetonitrile group was introduced, the compounds L6 and L7 were obtained with similarly aggregation induced properties, and further regulated the optical properties by increasing conjugate degree of molecule and strong electron-withdrawing ability of the nitro group. Eventually, the mechanism of aggregation induced emission was studied and the correlation between structure and property was summarized by exploring aggregation induced luminescence properties.