The Study Of The Synthesis And Properties Of Fluorescent Molecular Sensors Based On A 6-aryl[1,2-c]Quinazoline-diarylethene

Fluorescence chemosensor has a significant potential foreground in food analysis, process control, environmental monitoring, catalysis, bioluminescence imaging, medical diagnosis and so on. Due to the potential applications to many fields, photochromic compounds as functional materials have been widely focused. In particular, diarylethenes have become the promising candidates of photochromic compounds because of the excellent thermal stability of both isomers and resistance to high fatigue. So far, the new groups have been incorporated into the photochromic dithienylethene unit with a view to optimizing the photochromism and giving rise to some novel properties, which are hotspots in this filed. As far as we are aware, recognition of cations and anions at the same conditions based on diarylethenes has rarely been reported.The introduction of 6-aryl[1,2-c]quinazoline groups at the end of aromatic aldehyde expect better modulation the photochromic properties of the diarylethenes in structure and performance is the focus of this thesis research. This thesis mainly studies tne influence of diarylethenes compounds in the acid effect, the response of metal ions and anions, conjugate effect, electron-withdrawing substituent or electon-donating substituent and so on. The main research results are generalized as follows:This article were designed and synthesized seven kinds of novel asymmetric photochromic diarylethenes containing 6-aryl[1,2-c]quinazoline groups. Their structures were characterized by NMR, elemental analysis and IR.Photochromic properties of these diarylethenes in different medium such as in acetonitrile and methanol solutions were studied. The result shows that the compounds DT-1-5 are exhibited good photochromic properties in acetonitrile, and the compounds DT-6 and DT-7 are exhibited good photochromic properties in both methanol.The length of the conjugated chain and different substituents the have notable effects on the properties of these diarylethenes were investigated in detail. The study of conjugated chain length showed that the absorption maximum for both open-ring and closed-ring isomers of the long π-conjugated chain containing compounds DT-2 significantly increscent, but the molar absorption coefficient and the photoconversion were decreased significantly. Compared with the parent diarylethene containing formyl group, the emission intensity of DT-1-2 was much stronger, indicating that the emission intensity of diarylethenes with 6-aryl[1,2-c]quinazoline was enhanced significantly. For the derivatives DT-3-5, compared with the parent diarylethene DT-4, which terminal benzene ring has no substituents, the substituents effect results suggest that no matter replacing the hydrogen atom at the para-position of the therminal benzene ring with electron-withdrawing substituent or electon-donating substituent the molar absorption coefficient of the diarylethenes had clearly increased. When the terminal benzene ring has electro-withdrawing substituent, the fluorescence intensity and fluorescence modulation efficiency increased.The effects of acid were studied. Addition of TFA to DT-1C in acetonitrile resulted in the absorption maximum redshifted from 589 nm to 594 nm, accompanied with a notable color change from blue to green. The protonated DT-1C could return to the initial state of DT-1C by neutralizing with TEA. What is more, when TFA was added to the acetonitrile solution containing DT-1O, the emission peak was redshifted and the emission intensity was remarkably enhanced. Then, the fluorescence spectrum of DT-1O’ could return to the initial state DT-10 by neutralizing with TEA. Similar to DT-1O, the photochromism and fluorescence of DT-2 also exhibited multi-addressable behaviors by the stimulation of both light irradiation and acid/base.The metal cation respond was studied. The diarylethene DT-3 can serve as a ratiometric fluorescent chemosensor for highly selective recognition of Cu2+. The fluorometric titration for recognition Cu2+ showed two distinct processes in acetonitrile. In the first phase, the emission intensity at 427 nm decreased notably and a strong emission peak at 489 nm emerged accompanying a good linear relationship between the fluorescence intensity ratio (I489nm/I427nm) when the concentration of Cu2+ was less than 1.0 equiv. And that DT-3O-Cu2+(formed in the first process) exhibited remarkable fluorescence switch property by photoirradiation. In the second one, the emission intensity at 489 nm dramatically decreased when the concentration of Cu2+ increased from 1.0 to 10.0 equiv. After addition of 10.0 equiv of Cu2+, the fluorescence intensity at 489 nm was quenched ca.93%.The non-metal anion respond was studied. Among various kinds of anion F-, Cl-, Br-, I-, NO3-, SON-, HSO4-, PO43-, HCO3-, CH3COO-, and SO42-, the compound DT-3 can realize specificity response to HSO4- through intermolecular hydrogen bond. Compared to DT-3O, the emission peak of DT-3O-HSO4- was red-shifted by 64 nm with an enhanced intensity of 5 fold.The optoelectronic properties of ferrous ion complex were studied. The synthesis of the complex opened up a new path for the diarylethenes.