[en] Thermotropic nematic and chiral-nematic poly(p-phenylene)s were prepared into well-aligned films between fused-silica substrates in which conjugated backbones were uniaxially and helically oriented. With unpolarized photoexcitation at 350 nm, a nematic film produced a degree of linear polarization of 9 near the emission peak at 410 nm with no evidence of excimer formation. With the same photoexcitation of a chiral-nematic film, the degree of circular polarization was found to vary from -1.3 in the 390--430 nm spectral region to between +0.3 and +0.9 beyond the edge of the selective reflection band. The crossover behavior unique to light emission from the selective reflection region remains inexplicable with existing theories on light propagation through periodically structured films

[en] An highly efficient, economical, solvent-free methodology has been adopted for the synthesis of various heterocycles from o-phenylenediamine. Coupling of this new, environmentally benign, versatile, route with microwave (MW) apart from eliminating organic solvents from the reaction step offer benefits of shorter reaction times, higher yields and uniform heating effect

[en] In the context of luminescence from the solid state of poly(para-phenylene vinylene)-type materials, we report a study of three octyloxy-substituted five-ring oligo(para-phenylene vinylene)s, two of which bear cyano substituents on the innermost vinylene bonds. For each compound, the molecular arrangement in the single crystal has been derived from a crystallographic analysis. For the compound which has the cyano group not directly adjacent to the central ring, synthesis and structure are described here in detail. This compound, in contrast to the other two, has molecular π-stacking in the crystal lattice. Only for this compound do we observe a strongly red-shifted, long-lived emission, which is therefore ascribed to an excimer-type intermolecular excitation. The observations of excimer-type emission from cyano-substituted alkoxy-PPV's and in related copolymers fit in very well with the molecular picture derived from this study of model compounds. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

No abstract available

[en] Results are reported in a program to design, synthesize, and evaluate polycyclic host organic compounds for their abilities to complex and lipophilize guest metal ions. Work during the reporting period was devoted to synthesis and study of cyclohexametaphenylenes and cyclic phosphine oxides

[en] Organic electronics, mainly due to the advancement of OLED (Organic Light Emitting Diode) technology, is a fast developing research area, and has already revolutionized the displays market. This direction presents the use of exciplex emitters and thermally activated delayed fluorescence (TADF) in OLEDs. This is shown through electrochemical characterisation of six p-phenylene derivatives for application in optoelectronic devices and presents the possibility the compounds’ use as OLED emitters. In these OLED devices, it is established that selenophene based compounds with a “heavy-atom effect” can be used as potential emitters when exciplex phenomena are involved.

No abstract available

[en] Ethyl-adamantyl side groups substituted onto para-bis(2-thienyl)phenylene, a solid-state fluorescent dye, were found to induce π–π interactions between the conjugated para-bis(2-thienyl)phenylene cores. At the same time, stacking between the central unit and the adamantyl-containing side group was observed. As a result, due to steric hindrance augmentation of the solid-state, luminescence was observed. Moreover, substitution of standard alkyl side chains with ethyl-adamantyl groups resulted in raising the melting point temperature from 55 °C to ~250 °C. Aside from possible further-functionalization of the para-bis(2-thienyl)phenylene conjugated unit, aforesaid approach can be applied in a wide range of molecules and polymers, when luminescent properties and thermal stability can be tune through the side-chain engineering of organic materials.

[en] Short communication

[en] Solvent extraction behaviors of Se (VI) from nitric acid solutions were investigated with multiple extractants used for uranium, plutonium, minor actinides, and rare earth elements separation processes from high-level liquid waste. During the processes, Se remained in the residual aqueous solutions, as all extractants showed distribution ratios < 1. In contrast, Se showed distribution ratios > 1 with o-phenylenediamine in dilute nitric acid (< 2 M HNO₃), octanol as the organic phase, and concentrated nitric acid (8 M HNO₃) for back extraction, suggesting a potential new single separation process and recovery of Se. (author)