We have synthesized a novel 9,9′-spirobifluorene-cored donor-acceptor (D-A) bichromophore system in which the electron-donating (D) moieties are triphenylamine (TPA) and carbazole (CBZ) groups and the electron-withdrawing (A) moieties are 1,3,4-oxadiazole (OXD) groups. The electron-deficient OXD groups efficiently blocked the radical cations delocalization between the two terminal TPA groups, rendering the electropolymerization of the TPA groups feasible. The resulting polymer could be cross-linked further at higher oxidation potentials through electrodimerization occurring at the C3 and C6 positions of the CBZ group. The polymer film obtained exhibited reversible electrochemical oxidation, accompanied by strong color changes with high coloration efficiency and contrast ratio, which could be switched through potential modulation.

Oligoaryl is an important class of compounds which exhibit a variety of fascinating properties for optoelectronic interests. 1 Incorporation of five-membered heteroaromatic moieties into these conjugated molecules will occasionally increase fluorescence quantum yields and the optoelectronic properties of the oligomers can be tuned. 1 Most syntheses of these heteroaromatic containing oligomers involve the transition-metal catalyzed cross coupling reactions of the corresponding aryl components. 2 In general, the presence of a long chain aliphatic substituent in these heteroaromatic rings will increase the solubility in organic solvent and hence enhance the processibility of these materials. 1 However, introduction of such alkyl substituent at C 3 and/or C 4 positions in these heteroaromatic rings for further cross coupling reactions is not trivial. 3 Cyclization of the 1,4-dicarbonyl moiety with heteroatom-containing reagents provides an alternative procedure for the construction of these five-membered heterocycles. [3][4][5] It is known that annulation of allenylmethanols can afford the corresponding five-membered oxygen heterocycles. 6 In addition, annulation of allenyl carbonyl compounds, 7 propargylic acetals, 8 or oxiranes 9,10 furnishes a powerful arsenal for the synthesis of substituted furans. The applications of propargylic metallic species have paved a useful path for the construction of furan skeletons. 11 We recently reported that propargylic dithioacetal 1 can serve as an allene 1,3-zwitterion synthon (eq 1). 12 The interesting feature for this reaction involves an umpolung of one of the two carbonsulfur bonds in the dithioacetal functionality. The organocopper intermediate 2 can react with a number of electrophiles leading to either allenyl or alkynyl product 3 or 4. The chemoselectivity of this reaction depends on the nature of the electrophile. It is envisaged that the reaction of 2 with an aldehyde 6 or an aldimine 8 may yield the intermediate alcohol 5a, or amine 5b, respectively.

[structure: see text] Novel ter(9,9-ditolylfluorene) analogues containing thiophene and pyridine rings embedded as functional constituents within the parent hydrocarbon backbone have been synthesized. These new molecules exhibit highly efficient photoluminescence and high thermal and morphological stability. The electronic structure of the terfluorene backbone is significantly perturbed, which allows modulation of the backbone energy levels.

We report on the triplet spectra and dynamics in two types of oligomeric films deposited by two different techniques: thermal evaporation and spin coating. The different molecular arrangement in both films is manifested in a red shift of the absorption, PL, and T1-Tn absorption spectra of the sublimated film relative to the spin-coated one. Triplet recombination dynamics studied with steady-state photoinduced absorption (PA) spectroscopy follow a dispersive bimolecular recombination model away from the trap filling regime. We obtained values for the triplet bimolecular recombination ratio (beta) of 3.4 x 10 (-14) and 1.1 x 10 (-15) cm3 s (-1) for evaporated and spin-coated film, respectively, the difference being attributed to diverse molecular arrangement in both films.

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We report on the characteristics of a host-guest lasing system obtained by coevaporation of an oligo(9,9-diarylfluorene) derivative named T3 with the red-emitter 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran dye (DCM). We demonstrate that the ambipolar semiconductor T3 can be implemented as an active matrix in the realization of a host-guest system in which an efficient energy transfer takes place from the T3 matrix to the lasing DCM molecules. We performed a detailed spectroscopic study on the system by systematically varying the DCM concentration in the T3 matrix. Measurements of steady-state photoluminescence (PL), PL quantum yield (PLQY), time-resolved picosecond PL, and amplified spontaneous emission (ASE) threshold are used to optimize the acceptor concentration at which the ASE from DCM molecules takes place with the lowest threshold. The sample with a DCM relative deposition ratio of 2% shows an ASE threshold as low as 0.6 kW/cm(2) and a net optical gain measured by femtosecond time-resolved pump-and-probe spectroscopy as high as 77 cm(-1). The reference model system Alq(3):DCM sample measured in exactly the same experimental conditions presents an one-order-of-magnitude higher ASE threshold. The ASE threshold of T3:DCM is the lowest reported to date for a molecular host-guest energy-transfer system, which makes the investigated blend an appealing system for use as an active layer in lasing devices. In particular, the ambipolar charge transport properties of the T3 matrix and its field-effect characteristics make the host-guest system presented here an ideal candidate for the realization of electrically pumped organic lasers.

A bifluorene analogue, T2N, containing a pyridyl moiety serves as both a host and an efficient electron-transporting material that is compatible with various heavy metal-containing red (Ir, Ru, Os, and Pt) and green (Ir) phosphors for highly efficient phosphorescent OLEDs possessing simple device architectures.

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