Synthesis And Properties Of Novel Fluorescent Dendrimers Containing 1, 3, 5-Triazine

2,4,6-Trichloro-1,3,5-triazine (TCT) and aliphatic diamine were used as primary raw materials to synthesize dendrimers containing 1,3,5-triazine. Because of high stability of the 1,3,5-triazine ring which can bear harsh reaction conditions, and good chemo selectivity and reaction controllability of three chlorine atoms in TCT structure,protect-deprotect or deactivation-activation steps during the course of dendrimer synthesis were greatly reduced. In this paper, a series of novel dendrimers containing 1,3,5-triazine were synthesized by divergent strategy, and fluorescent dendrimers containing 1,3,5-triazine were achieved by the dendrimers functionalized with 1,8-naphthalimide. Furthermore, the solubility, thermostability, UV/Vis absorbent and fluorescent performance of the obtained dendrimers have been investigated. It can be summarized as follows:1. Improvement of synthesis method of mono-protected ethylenediamine: The method of protecting one of the amino groups in ethylenediamine (EDA) with di-tert-butyl dicarbonate (Boc acid radical) based on the literature was modified and higher yield of mono Boc group protected EDA (Boc-NHCH2CH2NH2, EDA-Boc) was obtained.2. Synthesis and characterization of dendrimers containing 1,3,5-triazine: The first generation dendrimer G1.0(Cl)4 was synthesized with hexylene diamine (HDA) as the core material and TCT as the branching monomer. Afterwards, Boc-terminated 1.5 generation dendrimer G1.5(Boc)4 were prepared from G1.0(Cl)4 reacting with tert-butyl-ethylenediamine-1-carboxylate. Furthermore, G1.5(Boc)4 were deprotected and reacted with TCT to form 2.0 generation dendrimer G2.0(Cl)8. Also, the synthetical conditions of each generation dendrimer were optimized by orthogonal experiments. All the dendrimers had good yields, and their structures were characterized by elementary analysis, MS, 1 H-NMR and FTIR.3.Preparation of novel fluorescent monomer: 4-hexylene diamine -N-butyl-1,8-naphtha-imide (HBNT) was synthesised by HDA reacting with 4-bromine-N-butyl-1,8-naphthali- mide. This compound have strong fluorescence, good solubility and less steric effect, which are favored to functionalize dendrimers.4. Synthesis and characterization of fluorescent dendrimers: G1.0(Cl)4 and G2.0(Cl)8 were functionalized by HBNT. Fluorescent dendrimer G1.0(HBNT)4 and G2.0(HBNT)8 were got and the structure of them was characterized by elementary analysis, MS, 1 H-NMR and FTIR.5. Investigation of the solubility and thermostability of the dendrimers: The solubility and thermostability of G1.0(Cl)4, EDA-Boc, G1.5(Boc)4, G2.0(Cl)8, HBNT, G1.0(HBNT)4 and G2.0(HBNT)8 were investigated. It was found that G1.0(Cl)4 was soluble in dimethylsulfoxide, partly soluble in 1,4-dioxane, acetone, dichloromethane, chloroform, methanol, tetrahydrofuran, N,N-dimethylformamide; G2.0(Cl)8 was soluble in dimethylsulfoxide and partly soluble in N,N-dimethylformamide; EDA-Boc and G1.5(Boc)4 were soluble in all commonly used solvents, HBNT and G1.0(HBNT)4 could be dissolved in a lot of solvents, such as ethanol, dichloromethane, chloroform, tetrahydrofuran, N,N-dimethylformamide and dimethylsulfoxide; G2.0(HBNT)8 was soluble in tetrahydrofuran, N,N-dimethylformamide and dimethylsulfoxide. All the products have good thermostability.6. Study on absorption and emission spectra of the fluorescent dendrimers: The UV/Vis absorption and fluorescent emission spectra of HBNT,G1.0(HBNT)4 and G2.0(HBNT)8 were tested. The order of the absobtance of their solutions with same concentration is G2.0(HBNT)8 > G1.0(HBNT)4 > HBNT, and UV/Vis absorption is influented by solvents; the fluorescent intensity of their DMF solutions increased at first, then decreased when the concentration rose, and at 5*10-5 mol/L HBNT solution got its maximum, while the fluorescent intensity of G1.0(HBNT)4 and G2.0(HBNT)8 solutions got their maximum at 1*10-5 mol/L. The fluorescent intensity is G2.0(HBNT)8 > G1.0(HBNT)4 > HBNT within the concentration 1*10-5~1*10-6 mol/L; solvents have large influence on fluorescent intensity and maximum fluorescence wavelength. Furthermore, the fluorescence quantum yield and Stokes shift of HBNT, G1.0(HBNT)4 and G2.0(HBNT)8 were evaluated with Rhodamine B as standard.