Synthesis And Self-Assembling Behaviors Of Nitrogen-Doped Heteropolycyclic Aromatic Hydrocarbons

Self-assembled nanoobjects consisting of functionalπ-conjugated organic molecules have attracted increasing attention due to their potential applications in organic and supramolecular electronics. Polycyclic aromatic hydrocarbons are often utilized as building block for construction of these materials. To date, a great number of PAH derivatives with different geometry and substituent have been designed and achieved, however, synthesis and characterization of heteroatom doped-PAH derivatives are still rare. Partially introducing heteroatom, such as nitrogen, into the all carbon aromatic skeleton of PAHs will usually lead to dramatic changes in their physicochemical and/or electronic properties. This thesis described the design of novel nitrogen-doped hetero PAH derivatives, and sysmatic studied on their synthesis, physicochemical features and self-assembling behaviors. The main contents are as follows:1. The synthesis of nitrogen-doped polycyclic aromatic hydrocarbons. We designed four kinds of nitrogen-doped polycyclic aromatic hydrocarbons, and precursors 2-29,2-30 and 2-36 were successfully synthesized from bromobenzene as starting material by several steps. Nitrogen-doped PAH4 was synthesized by Scholl-type oxidative cyclization of the corresponding precursor 2-36 using FeCl3 (36 eqv) as a mild oxidant in CH2Cl2/MeNO2 for 4 hours. However, precursor 2-29 and 2-30 under the same conditions gave insoluble solids, MALDI TOF Mass results showed that solid are mixture containing partially dehydrogen by-products, decomposed component and chlorinated compounds etc.2. Physicochemical properties and self-assembling behaviors of the compound PAH4 were inverstigated. The physicochemical properties of PAH4 were characterized by FTIR, UV-vis, fluorescence spectrometry, differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) measurements. And the self-assembling behaviors of PAH4 were discussed in different solvents. TGA result indicated that nitrogen-doped PAH4 exhibiting high thermostability which will decomposed over 374.3℃. When a diethyl ether vapor was allowed to diffuse at 25℃into a CH2Cl2 solution of PAH4, a black suspension was resulted. Scanning elelctron microscopy (SEM) of an air-dried sample of the suspension showed rod-like nanostructures. The fluorescence nature of PAH4 depending on the solvent, for example, it showed a yellow fluorescence in CH2Cl2 and orange fluorescence in THF or toluene.'H NMR, UV-vis and fluorescence spectra showed broad peaks, and these results suggested that nitrogen-doped PAH4 existed in certain dynamic aggregates in those solutions via intermolecularπ-πinteractions.