Design And Investigation Of Fluorescence Chemsensors Based On Hexaazatriphenylene Derivatives

In recent years, the detection and recognition of metal ions have become a focus of intense research activities in the fields of cation recognition. Due to the operability and fast-speed, fluorescence sensors are powerful tools for the detection of metal ions, which are widely used not only in environmental monitoring but also in biological studies. The key for selective recognition of metal ions is to design a fluorescence sensor with high sensitivity and specific selectivity. Hexaazatriphenylene (HAT) and its derivatives, which are based on π-conjugated hexaazatriphenylene core and can be readily modified by their six substituent groups, have potential ability to coordinate with specific metal ion.In this dissertation, a serious of phenyl-/pyridyl-/methyl-substituent HAT derivatives were designed and synthesized by the condensation reaction of1,2-diamines and1,2-diketones. The recognition behaviors of these compounds to different metal ions in solution were investigated, and the results indicated that the compounds have fluorescence selectivity to Zn2+, Cd2+, Al3+, respectively. The self-assembly of the compounds with the metal ions were further studied. The main points are summarized as follows:1. Two phenyl-/pyridyl-substituent HAT derivatives L1and L2with different chelating sites were designed and synthesized. Both compounds L1and L2exhibit sensitive, ratiometric and colorimetric fluorescent selectivity for Zn2+ion over alkali ions, alkaline earth ions and a wide range of transition metal ions based on intramolecular charge-transfer (ICT) mechanism in acetonitrile and in5%aqueous acetonitrile. The interaction between L1or L2and Zn2+can be observed by naked eyes with an obvious color change of the solution from colorless to yellow and fluorescence color change from blue to yellow. The stoichiometry and coordination mode of L1-Zn2+and L2-Zn2+were determined with fluorescence titration fit, job’s plot analysis,1H NMR titration and X-ray crystallography. The results show that L1and L2have potential applications in Zn2+fluorescence sensors. Furthermore, the photophysical and electrochemical properties of a serious of HAT derivatives with different number of phenyl and pyridyl were also studied.2. Two phenyl-/methyl-substituent HAT derivatives L3and L4with different chelating sites were designed and synthesized. Both L3and L4exhibit high off-on fluorescent selectivity for Cd2+over many other metal ions based on the chelation enhanced fluorescence (CHEF) mechanism in acetonitrile and in5%aqueous acetonitrile. The stoichiometry of L3-Cd2+and L4-Cd2+were determined with fluorescence titration fit, job’s plot analysis,1H NMR titration and X-ray crystallography to be1:2and1:3, respectively. The recognition mechanism of sensors L3and L4to Cd2+was further analyzed with density functional theory calculation. Since the high sensitivity and selectivity to Cd2+, L3and L4are ideal Cd2+fluorescence chemsensor. What’s more, we also studied the self-assembly of the compounds with transition metal ions.3. A compound analogous to HAT derivatives L5was designed and synthesized. L5shows high off-on fluorescent selectivity for Al3+over many other metal ions in acetonitrile. The competition experiments and the detection limit of L5to Al3+indicated that L5can recognition Al3+sensitively and without interference by other metal ions.Above all, the studies increase the knowledge of design and synthesis of HAT derivatives and provide novel Zn2+, Cd2+, Al3+fluorescence chemsensors based on HAT derivatives.