Modulate photoinduced electron transfer efficiency of bipolar dendritic systems

Synthesis and fluorescence properties of two dendritic molecules based on naphthalimide and triphenylamine

Artificial light-harvesting systems have attracted great interest in biological photosynthesis and photo-voltaic devices areas due to their unique structures, easy purification, low-cost, and convenient processing abilities. Here, two dendritic molecules based on triphenylamine and naphthalimide have been designed and synthesized, their structures were confirmed by ¹ H NMR, ESI-MS, and high resolution mass spectrometry. In these molecules, triphenylamine units perform as the electron donor moiety, and naphthalimide units perform as the electron acceptor. The obvious quenched fluorescence intensity and considerably shortened lifetime of the dendritic molecules combined with the molecular frontier orbital energy levels proved that the dendritic molecules not only are good candidates as hole-transporting materials but also are two excellent photo-induced electron transfer materials. Therefore, it is believed that these dendritic molecules have potential application value in photo-voltaic devices.

Blue Light Emitting Polyphenylene Dendrimers with Bipolar Charge Transport Moieties

Two light-emitting polyphenylene dendrimers with both hole and electron transporting moieties were synthesized and characterized. Both molecules exhibited pure blue emission solely from the pyrene core and efficient surface-to-core energy transfers when characterized in a nonpolar environment. In particular, the carbazole- and oxadiazole-functionalized dendrimer (D1) manifested a pure blue emission from the pyrene core without showing intramolecular charge transfer (ICT) in environments with increasing polarity. On the other hand, the triphenylamine- and oxadiazole-functionalized one (D2) displayed notable ICT with dual emission from both the core and an ICT state in highly polar solvents. D1, in a three-layer organic light emitting diode (OLED) by solution processing gave a pure blue emission with Commission Internationale de l’Éclairage 1931 CIE xy = (0.16, 0.12), a peak current efficiency of 0.21 cd/A and a peak luminance of 2700 cd/m². This represents the first reported pure blue dendrimer emitter with bipolar charge transport and surface-to-core energy transfer in OLEDs.

Applications of Palladium-Catalyzed C-N Cross-Coupling Reactions

Pd-catalyzed cross-coupling reactions that form C–N bonds have become useful methods to synthesize anilines and aniline derivatives, an important class of compounds throughout chemical research. A key factor in the widespread adoption of these methods has been the continued development of reliable and versatile catalysts that function under operationally simple, user-friendly conditions. This review provides an overview of Pd-catalyzed N-arylation reactions found in both basic and applied chemical research from 2008 to the present. Selected examples of C–N cross-coupling reactions between nine classes of nitrogen-based coupling partners and (pseudo)aryl halides are described for the synthesis of heterocycles, medicinally relevant compounds, natural products, organic materials, and catalysts.

Solution-processed bulk-heterojunction photovoltaic cells based on dendritic and star-shaped D-pi-A organic dyes

A series of D-pi-A organic dendritic and star-shaped molecules based on three various chromophores (i.e., the truxene nodes, triphenylamine moieties as the donor, and benzothiadiazole chromophore as the acceptor) and their corresponding model compounds are facilely developed. Their photophysical and electrochemical properties are investigated in detail by UV/Vis absorption and photoluminescent spectroscopy, and cyclic voltammetry. By changing the various conjugated spacers (i.e., single bond, double bond, and triple bond) among the three chromophores of dendritic series, their photophysical properties (that is, the one-photon absorption range and two-photon absorption cross-section values) are effectively modulated. All D-pi-A conjugated oligomers show a broad and strong absorption band from 250 to 700 nm in thin films. Solution-processed bulk-heterojunction photovoltaic devices using our oligomer as donor and PCBM as acceptor are fabricated and measured. The power conversion efficiency of the devices based on our oligomers continuously increases from DBTTr to TrTD2A as a result of an increasing relative absorption intensity in longer wavelength region by changing the donor-acceptor ratio and conjugated spacers between the donor and acceptor. The power conversion efficiency of the devices based on TrTD2A was 0.54% under the illumination of AM 1.5 and 100 mW cm(-2), which is the highest value recorded based on D-pi-A conjugated oligomers containing triphenylamine moieties and benzothiadiazole chromophores with truxene to date.