Synthesis And Properties Of Triphenylamine-based Dendrimers & Oligo(Phenothiazine)s

The design of novelπ-conjugated systems and its optic-electronic properties studies have attacted increasing attention in these years, since functional molecular materials have been proved their high potential applications in solar cell,organiclight-emitting diodes(OLEDs),sensors,field-effect transistors, etc. Compared with traditional conjugated polymers, monodisperse conjugated oligomers have well-defined chemical structures, so they become ideal models for understanding the structure-property relationships of the corresponding polymers. Otherwise, we could regulate the conjugated degree of organic molecules and its optic-electronic properties by molecule designing. Up to now, we have synthesized a great number of linear, star-shaped and dendritic oligomers which have different structures, and applied them to organic molecular devices. We begin with functional assemblies principles, take advantage of modifiable quality of organic molecular structure, design and synthesize two series of organic optoelectronic functional materials, and study the relationships of structure-property in details. The detailed content of my dissertation as stated below.The studis of triphenylamine (TPA) are attatched more and more attention because of its excellent thermal and electrochemical stability, electron donating ability, and good optoelectronic properties as well as three-dimensional propeller structure. We develop a new way of synthesizing triphenylamine-based dendrimers by connecting triphenylamine through C-C double bond. It is a convergent synthetic strategy without any protection-deprotection chemistry, so less steps is needed and more production can be obtained. Based on these work, we design and synthesize three novel dendrimers(G0, G1 and G2) with symmetrical donor-π-bridge-acceptor-π-bridge-donor (D-π-A-π-D) structure with sulfonyldibenzene as the core and the triphenylamine as dendrons through Heck and Witting reactions. They are characterized by 1H NMR, 13C NMR, FT-IR, elemental analysis and MALDI-TOF mass spectra. We find that their thermal, optical and electrical properties are manipulated by attaching different peripheral dendrons. In order to investigate the electron distribution of the LUMO and HOMO energy level of the dendrimers, quantum-chemical calculations were carried through the Gaussian 03 program at the B3LYP/6-31G* level. Quantum-chemical calculation of electronic structure shows that the HOMO is localized on the triphenylamine donor moiety, while LUMO is localized on the sulfonyldibenzene acceptor moiety, and proves a significant charge-transfer from donor miety to acceptor moiety. These conjugated dendrimers have good solubility in the common organic solvents, such as chloroform, dichloromethane etc., and could form excellent-quality optical films by spin coating. Using these dendrimers as donors and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) as acceptor, the bulk heterojunction solar cells with a structure of ITO/PEDOT/dendrimers: PCBM/LiF/Al were fabricated. The cells based on these dendrimers show power-conversion efficiency (PCE) of 0.34%, 0.19% and 0.06%, respectively.Phenothiazine is a well-known heterocyclic compound with electron-rich sulfur and nitrogen heteroatoms. It have a rigid structure, largeπconjugated system, excellent holetransporting property, and a low ionization potential. But its research do not start until recent years as a electroluminescence materials. Phenothiazine's chemical property major in substitution reaction happned on nitrogen atom and benzene ring, for example, N-alkylation reaction, Vilsmeier reaction, oxidation reaction on nitrogen and sulfur atom, and so on. A series of linear monodisperse vinylene-linked phenothiazine oligomers containing anthracene have been designed and synthesized after our consideration. It has a characteristic aggregation induced emission(AIE) property when we study its photophysical properties. Its AIE property is similar with that of three conjugated dendrimers with triphenylamine-based branches and anthrylene core (An-TPA2, An-TPA6, An-TPA14)we have reported before. We design and synthesize two monodisperse conjugated oligomers containing anthracene (An-PHZ2, An-PHZ4)by convergent iterative synthesis method. Their stucture are characterized by 1H NMR, 13C NMR, FT-IR, elemental analysis and MALDI-TOF mass spectra. We use Heck reaction to make sure the goal molecules to be trans-structure because the functional groups of the molecules are connected by double bonds. We find that they show stong IR absorption around 960 cm-1, which are characteristic aborption area of trans-double bond, so we assure that the molecules are all trans-structure. They show relatively faintly luminescence or even nonemission in solutions, but show strong luminescence at aggregate state(nano particles or thin solid film), in other words, they have characteristic AIE property. We further study their spectral qualities when they are in a poly(methyl methacrylate) (PMMA) film and frozen in the distorted form. We think the molecules in monomolecular state as the oligomer molecules are monodiperse in PMMA film. They have strong luminescence when they are in PMMA film and forzen state(77K). Under such conditions, distorted An-PHZ and An-PHZ4 are fixed. The molecules are in a excited state when light stimulus, the intromolecular nono-radiative free rotation hardly happen. Thus, An-PHZ2 and An-PHZ4 show a good luminescent properties. The AIE property come from not only molecular aggregates but also the special molecular structures. We find that the characteristic AIE property of the molecules rise from the 9,10-anthrylene core after we compare their molecular stuctures and spectral properties, which is consistent with the work before in our group.