Synthesis And Properties Of Multi-benzene Substituted Fluorescence Molecules With Mechanochromism And Zn²⁺?Hg²⁺ Recognition Characteristics

Until now,the potential application of high-efficiency organic luminescent materials in sensors,optoelectronic storage devices and organic light-emitting diodes has attracted the interest of researchers.It is well known that most conventional organic luminescent materials has been give rise to a phenomenon called aggregation-caused quenching?ACQ?.Fortunately,in 2001,Tang et al.reported a fluorescent molecule named 1-methyl-1,2,3,4,5-pentaphenylsilole.Interestingly,the fluorescent emission of this luminogen was induced by aggregation,a phenomenon referred to as aggregation-induced emission?AIE?.In addition,fluorescent molecules with AIE properties have attracted more and more attention from researchers in the field of fluorescent sensors,especially for the detection of metal ions.At the same time,Conventional sensors mostly detect metal ions in organic solvents,and there are relatively few reports on detection in water-containing mixed solvents,and the detection of metal ions in a mixed system containing water is also greatly increased practical application of the sensor.More interestingly,there are many fluorescent molecules with AIE properties that also have mechanochromic properties,while some molecules with mechanochromic properties have practical application value in the fields of coin anti-counterfeiting and inkless writing.Based on the above research background,in this paper,we synthesize a series of highly fluorescent emission molecules with mechanochromic properties through reasonable molecular design and practical feasibility analysis.Additionally,through introducing a highly fluorescent unit 1,8-naphthylimide into the triphenylamine unit,three luminescent molecules having highly aggregated emission and mechanochromic properties while having solvatochromic properties were synthesized;on the other hand,using tetraphenylethylene?TPE?as a precursor,three fluorescent molecules with AIE properties and used of detect metal ions were synthesized by Suzuki coupling reaction.The main contents are shown as following:1.This paper introduces the research background of AIE,the research overview of compounds with AIE and stimuli-responsive properties,as well as the research of compounds with AIE properties in fluorescence sensors as Zn²⁺and Hg²⁺.Through the systematic study of photochemical properties,the content of this topic is proposed.2.We introduced the highly fluorescent unit 1,8-naphthylimide into the triphenylamine?TPA?unit by Suzuki coupling reaction,and designed and synthesized three fluorescent molecules of M-1,M-2 and M-3.The length of the base chain in1,8-naphthalimide unit is used to study the photochemical properties of such fluorescent molecules.The research results show that the length of the alkyl chain does not affect its photochemical properties,and three compounds have high aggregation luminescence behavior and mechanochromic properties.3.Three multifunctional TPE derivatives?M-4,M-5 and M-6?are linked to TPE by a Suzuki coupling reaction with groups of different recognition sites.The experimental results show that all three molecules have AIE properties,while both molecules M-4 and M-5 have mechanochromic properties,while molecule M-6 does not have this property,but interestingly,molecule M-6 has significant solvatochromic properties.In addition,all three molecules are capable of detecting Zn²⁺and Hg²⁺in different systems.Molecules M-4 and M-5 were able to recognize Zn²⁺in a pure tetrahydrofuran solution.The two molecules showed none fluorescent emission in pure tetrahydrofuran solution while showed bright orange-yellow fluorescence after addition of Zn²⁺.Moreover,Hg²⁺can be identified in a tetrahydrofuran-water?f_w=90%?mixed solution?nano-aggregated state?.The two molecules exhibited bright blue-green fluorescence in a tetrahydrofuran-water?f_w=90%?mixed solution,and showed significant fluorescence quenching after the addition of Hg²⁺.However,molecule M-6 recognizes Hg²⁺in a pure acetonitrile solution.Indeed,this molecule exhibited orange-red fluorescence in pure acetonitrile solution and fluorescence quenching after addition of Hg²⁺.Furthermore,the molecule can also be used for superior cell imaging.