Preparation, Structure-activity Relationship And Biological Application Of Triphenylamine Derivatives Fluorescent Probe

Triphenylamine (TPA), which is structured a star-like geometry with a nitrogen atom in the center, is widely used in photoelectric materials and hole-transporting materials due to its unique free radicals, larger steric hindrance factors, super conjugate electronic effect and high hole mobility. Three benzene rings linked with the nitrogen atom of triphenylamine, with its obvious activity, structural diversity and easily modified property, can be connected with external substituents at appropriate positions and a series of luminescent materials with certain functions can be produced. With a comprehensive survey of application studies of triphenylamine fluorescent probe, we have prepared triphenylamine formylation derivatives through the Vilsmeier-Haack reaction and obtained a series of intermediate compounds through the multistep reaction. Based on these intermediates, a list of novel triphenylamine Schiff base compounds have been synthesized by the Witting reaction. The recognition ability toward metal ions were studied systematically, and explored the biological applications combined with the experiment results.The main research contents are as follows:1、With triphenylamine as donor center, on the one hand, we introduced isophorone red launch group through condensation reaction, on the other hand, connected the diaminomaleonitrile or thiosemicarbazide as the recognition groups containing multiple ligand atoms, to construct two new Schiff base fluorescent probes Lw and Lo. We studied their recognition ability toward metal ions by ultraviolet and fluorescence spectrum analysis methods. The experiment results showed that the probes were able to real-time monitor Cu2+ in acetonitrile solution via displaying the "turn-on" emission with high selectivity, sensitivity. Surprisingly, the compound Lo possesses two independently addressable photochromic systems based on the distinct mechanisms in tetrahydrofuran solution and solid state under the stimuli of UV/Vis light, however, we did not find this phenomenon for conpound Lw. By ultraviolet spectrum, fluorescence spectroscopy, mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy, we found that the thiosemicarbazide base of compound Lo occurred the intramolecular addition reaction, generated a stable pentabasic imidazole ring in THF solution, however, happened trans-cis isomerization in solid state under the stimuli of UV/Vis light.2、With triphenylamine as donor center, connected with C-N and styrene to building molecular skeleton, in which,4-diethylamino-2-hydroxyphenyl and hydroxyphenyl were selected as terminal groups, respectively, to synthesize triphenylamine Schiff bases. In the process of experiment, the nitro and the styrene were reducted to into amino and phenethyl, and accidentally got the nonconjugate triphenylamine Schiff base derivatives L1 and L2 when the Pd/C and hydrazine hydrate as the reducing agent. Furthermore, the influence of the gradual change in ability of donating/accepting electron, steric hindrance on recognition property were investigated. The experimental results showed that, L1 exhibited selective fluorometric sensing of Al3+ ions distinguished from other trivalent ions, which showed selective blue color generation from colorless for Bi3+, Fe3+, Cr3+ but green color only for Al3+. Whereas, by introduction the diethylamino group to L1, L2 displayed the obvious color change for Zn2+ ions up to ppm level by chelation-enhanced fluorescence (CHEF). Distinctive recognition mechanisms of L1 and L2 toward Al3+ and Zn2+ have been established by UV/vis, fluorescence spectra, mass spectra and 1H NMR studies, respectively. Above results motivate us to explore the potential application of L2 as an in cellulo Zn2+ indicator, as well as in live tissues under confocal laser scanning microscopy (CLSM). Furthermore, the experiment results suggested that L2 could be unitized as an attractive reagent for visualizing Zn2+ location and indicating Zn2+ concentration in living cells and tissues.3、With triphenylamine as donor center, connected with C=N and styrene, and by introducing the hydroxyphenyl as terminal group to synthesis the conjugate triphenylamine schiff base derivatives LW1. In the process of experiment, the styrene can be reducted into phenethyl to get the nonconjugate triphenylamine schiff base derivatives LW2 by changing the amount of rake carbon/hydrazine hydrate and the reaction time. The experimental results showed that these two triphenylamine Schiff base probe exhibited excellent recognition ability towards Al3+ via off-on fluorescent type with different mechanisms. The recognition mechanism of the Schiff base with double bond (LW1) is that the aluminum ion leads to hydrolysis at aldimine linkage and generate amine (T1) and by the decomposition of amine (T1) to the recognition of aluminum ion. However, the recognition mechanism of the schiff base with single bond (LW1) is that by chelation for specific recognition of aluminum ions.