Synthesis And Properties Of Fluorescent Chemosensors For Al³⁺ And Cu²⁺ Based On Rhodamine B Acylhydrazone

The problems of environment and health caused by metal ions were increasingly serious,which put forward higher request for detecting metal ions of low concentration in the aqueous medium even in living cells.As a kind of effective detection methods,fluorescence analysis method plays an important role in detection of metal ions.However,most of the probes of previous reports were single selectively,and the lower limit often could not meet the needs of the testing.Aim at above problems,three types of "off-on" fluorescent probes that could detect Al³⁺ and Cu²⁺respectively in different conditions were designed and synthesized by rhodamine B acylhydrazone based on the mechanism of PET,their structures were characterized by'HNMR and 13CNMR et al,their performance was tested using fluorescence spectrophotometer and ultraviolet visible spectrophotometer.1.With rhodamine B,hydrazine hydrate and several kinds of benzaldehyde containing electron-danationg group as raw materials,the lactone functional group of rhodamine B happened hydrazionlysis getting rhodamine B hydrazide 1,then 1 took place condensation reaction with aldehyde,a series of fluorescent probes containing electron-danationg group based on rhodamine B acylhydrazone were synthesized,which made one probe having multiple responses come true by detecting Al³⁺ and Cu²⁺ respectively with high selectivity in different solvent systems.This paper focuses on the performance of the probe 2a,it exhibited excellent selectivity for Al³⁺reversibly via a naked eye color change from colorless to pink in ethanol/H2O?2/3,V/V?buffer,and a 1:1 stoichiometry was the most likely binding mode between 2a and Al³⁺ with an association constant around 1.568 × 105 M-1.The detection limitcould reach 8.930 x 10-8 M.The probe could detect A1³⁺ with high selectivity within the scope of the pH 5-7.5.When in CH3CN/H20?3/2,V/V?buffer,the probe could detect Cu²⁺ selectively,the free probe displayed a very weak fluorescence,which indicated that the spirolactam form was the predominant species.When Cu²⁺ was added,the fluorescence intensity increased because the probe became the opened-ringform.A 1:2 stoichiometry was the most likely binding mode between 2a and Cu²⁺with an association constant around 5.424 × 106 M-1 and a limit of 12.4 nM.The probe could detect Cu²⁺ selectively within the scope of the pH 5-9.2.With rhodamine B,hydrazine hydrate and benzaldehyde containing ortho nitro,meta-nitro and para nitro as raw materials,the lactone functional group of rhodamine B happened hydrazionlysis getting the compound 1,then 1 took place condensation reaction with aldehyde,three fluorescent probes containing ortho nitro,meta-nitro and para nitro based on rhodamine B acylhydrazone were synthesized.This paper focuses on the performance of probe 3a.It could detect Al³⁺ and Cu²⁺ respectively with high selectivity through different response time and emission wavelength.The probe could react with Al³⁺ quickly with a wavelength redshift,while the response between probe and Cu²⁺ needed fifteen minutes and the emission wavelength stayed in the original position.The complex ratio of probe with two ions was both 1:1.The association constant between 3a and Al³⁺ was 7.816 × 107 M-1 and detection limit was 6.982 × 10-8 M,the probe could detect Al³⁺ within the scope of the pH 5-7.5.The association constant between 3a and Cu²⁺ was 5.207 × 107 M-1 and detection limit was 1.445 × 10-7 M.The probe could detect Cu²⁺ within the scope of the pH 5-11.3.With rhodamine B,hydrazine hydrate and o-chlorobenzaldehyde as raw materials,the lactone functional group of rhodamine B happened hydrazionlysis getting the compound 1,then 1 took place condensation reaction with aldehyde,one fluorescent probe containing chlorine based on rhodamine B acylhydrazone was synthesized?4a?,which could detect Al³⁺ and Cu²⁺ respectively with high selectivity through different instruments.The probe could recognize Cu²⁺ selectively with an ultraviolet spectrophotometer along with color change in the systems containing 90%ethanol.The identification of the process should be carried out in the sun,and in dark conditions and sunlight were reversible.A 1:1 stoichiometry was the binding mode between the probe and Cu²⁺ with an association constant around 4.394 × 105 M-1.The detection limit could reach 2.410 × 10-7 M.The probe could detect Cu²⁺ with high selectivity within the scope of the pH 3-8.The probe could recognize Al³⁺ selectively with a fluorospectro photometer along in the systems containing 40%CH3CN.A 1:1 stoichiometry was the binding mode between the probe and Al³⁺ with an association constant around 1.979 × 108 M-1.The detection limit could reach 1.466 × 10-8 M.The probe could detect Al³⁺ with high selectivity within the scope of the pH 5-7.5.It can be found that electron-danationg group can enhance fluorescence intensity and nitro and chlorine atom can reduce fluorescence intensity,but it will improve the ability of probe combining with ions by comparing three kinds of probe.Three kinds of probe showed excellent performance,they have very good application prospect.