Synthesis And Fluorescent Properties Of Ester Derivatives Of Benzo"5,6"counarin-3-carboxylic Acid

As good fluorescent whitening agents, laser dyes, fluorescent probes and nonlinear optical materials, coumarin compounds not only have excellent biological activity, but also have excellent optical properties. They are typical latctone compounds with lactone chromophore. Most of them are fluorescent, and used as fluorescent dyes. In order to obtain excellent organic electroluminescent materials, sensitive fluorescent probes for metal ion and be suitable with the development of fluorescence detection technologies, it is particularly important to design, synthesize and choose diverse fluorescent coumarin derivatives.The effect of fluorescence and the principles were discussed. According to the features of molecular structure, progress in fluorescent materials as typical organic pigments and the relationship between molecular structure and performance were reviewed. The performance parameters and test methods of fluorescent spectrum were analysed.Benzo[5,6]coumarin-3-carboxylic acid was prepared from 2-hydroxy-1-naphthaldehyde by Knoevenagel reaction. Based on coumarin, two kinds of benzo[5,6]coumarin-3-carboxylic ester, straight-chain alkanol ester derivatives and open-chain crown ether multi-glycol ester derivatives, were designed and synthesized through different approach and conditions. It consists of the following three aspects.In part one, four benzo[5,6]coumarin-3-carboxylic acid ester derivatives of straight-chain alkanol, namely, methyl benzo[5,6]coumarin-3-carboxylate(A), n-propyl benzo[5,6]coumarin-3-carboxylate(C), n-butyl benzo[5,6]coumarin-3-carboxylate(D), n-amyl benzo[5,6]coumarin-3-carboxylate(E), were designed and synthesized. n-Amyl benzo[5,6]coumarin-3-carboxylate (E) has not been reported in literature. In part two, six multi-glycol benzo[5,6]coumarin-3-carboxylate derivatives of open-chain crown ether, namely, triglycol benzo[5,6]coumarin-3-carboxylate(â… ), tetraglycol benzo[5,6]coumarin-3-carboxylate (â…¡), pentaglycol benzo[5,6]coumarin-3-carboxylate(â…¢), triglycol dibenzo[5,6]coumarin-3-carboxylate(â…£), tetraglycol dibenzo[5,6]coumarin-3-carboxylate(â…¤), pentaglycol dibenzo[5,6]coumarin-3-carboxylate (â…¥), were designed and synthesized. Compoundâ… ,â…¡,â…¢,â…¤,â…¥haved not been reported in literature.In part three, ethyl benzo[5,6]coumarin-3-carboxylate(B) was synthesized from 2-hydroxy-l-naphthaldehyde and diethyl malonate under microwave irradiation, catalyzed by piperidine. The best reaction conditions were determined by single factor optimization. Compared with conventional heating, microwave heating method shows its uniqueness.The product structures were confirmed by ¹H NMR, ¹³C NMR, FT-IR, MS and elemental analysis. The melting points of these compounds were determined. Their UV and fluorescence spectra were studied, and the values of the fluorescence quantum efficiency in different organic solvents were determined. The result shows that the products were strong fluorescent compounds and emit blue fluorescence. Dimethyl sulfoxide ( DMSO ) was their fluorescence quenching solvent. In acetonitrile, upon the addition of alkali metal cations ( Li⁺, Na⁺, or K⁺ ) or alkaline earth metal cations ( Mg²⁺, Ca²⁺, or Ba²⁺ ), theФF values of these multi-glycol benzo[5,6]coumarin-3-carboxylates changed. They showed some selectivity towards these cations. The addition of Ca²⁺ decreased the relative fluorescence intensities of compoundâ… andâ…¡to 0.73, 0.85, respectively. The relative fluorescence intensities of compoundâ…£,â…¤andâ…¥increased to 1.43, 1.42 and 1.48, respectively after adding Ca²⁺. The addition of Ba²⁺ decreased the relative fluorescence intensities of compoundâ…¤andâ…¥to 0.64, 0.55, respectively. These derivatives are potential organic electroluminescent materials and may be used as new fluorescent probes for metal ions.