Crystal Engineering of Room Temperature Phosphorescence in Organic Solids

We report a series of highly emissive azatriangulenetrione (TANGO) solids in which the luminescent properties are controlled by engineering the molecular packing by adjusting the steric size of substituents. The co‐alignment of “phosphorogenic” carbonyl groups within the π‐stacks results in an almost pure triplet emission in HTANGO, TCTANGO, TBTANGO and TITANGO, while their rotation by ≈60° in the sterically hindered tBuTANGO leads to an almost pure singlet emission. Despite strong π‐interactions, aggregation‐induced quenching and triplet–triplet annihilation are avoided in HTANGO and TCTANGO which display efficient phosphorescence in the solid state. To our knowledge, HTANGO with the solid‐state phosphorescence quantum yield of 42 % at room temperature is the most efficient phosphor composed of the 1^st/2^nd raw elements only.     

A Pure-Red Doublet Emission with 90 % Quantum Yield: Stable,Colorless, Iodinated Triphenylmethane Solid

Red luminescence is found in off-white tris(iodoperchlorophenyl)methane ( 3I-PTM^H ) crystals which is characterized by a high photoluminescence quantum yield (PLQY 91 %) and color purity (CIE coordinates 0.66, 0.34). The emission originates from the doublet excited state of the neutral radical 3I-PTM^R , which is spontaneously formed and becomes embedded in the 3I-PTM^H matrix. The radical defect can also be deliberately introduced into 3I-PTM^H crystals which maintain a high PLQY with up to 4 % radical concentration. The immobilized iodinated radical demonstrates excellent photostability (estimated half-life >1 year under continuous irradiation) and intriguing luminescent lifetime (69 ns). TD-DFT calculations demonstrate that electron-donating iodine atoms accelerate the radiative transition while the rigid halogen-bonded matrix suppresses the nonradiative decay.     

Fluorene Compounds with Intramolecular Charge Transfer Containing Dithiolylidene and Selenathiolylidene Substituents

Abstract

Condensation of polynitrofluorenes with dithiolium and selenathiolium salts in DMF leads to 9-substituted fluorenes with intramolecular charge transfer (ICT); spectral investigations show that ICT energies and intensities of ICT bands in electron absorption spectra depend substantially on heteroatomlocation but display very few dependence on the heteroatom nature (S or Se)     

Decarboxylation and ring fragmentation reactions of sydnone N-oxides

4-Carboxylated sydnone N-oxides are readily decarboxylated by benzylation to give 2,4-dibenzylsydnone-N-oxides. Ring cleaveage results from their oxidation with bromine which leads to a nitrile N-oxide which is isolated as its furazan dimer.     

Bending of a semi-infinite cantilevered plate weakened by a cut with contacting edges

We solve the problem of the bending of a semi-infinite cantilevered plate containing a cut perpendicular to a clamped edge. Contact of the edges of the cut is taken into account in the two-dimensional formulation on the basis of the model of contacting edges on the face of the plate. We study the effect of the boundary on the distribution of the contact reaction and compute the coefficients of force and moment intensity and determine the breakinge load. We compare the results obtained with the solution of the problem not taking account of the contact of the edges of the cut. Translated fromMatematichni Metodi ta Fiziko-Mekhanichni Polya, Vol. 40, No. 2, 1997, pp. 83–86.     

Crystal Engineering of Dual Channel p/n Organic Semiconductors by Complementary Hydrogen Bonding

The supramolecular arrangement of organic semiconductors in the solid state is as critical for their device properties as the molecular structure, but is much more difficult to control. To enable supramolecular design of semiconducting materials, we introduced dipyrrolopyridine as a new donor semiconductor capable of complementary hydogen bonding with naphthalenediimide acceptors. Through a combination of solution, crystallographic, and device studies, we show that the self‐assembly driven by H bonding a) modulates the charge‐transfer interactions between the donor and acceptor, b) allows for precise control over the solid‐state packing, and c) leads to a combination of the charge‐transport properties of the individual components. The predictive power of this approach was demonstrated in the synthesis of three new coassembled materials which show both hole and electron transport in single‐crystal field‐effect transistors. These studies provide a foundation for advanced solid‐state engineering in organic electronics, capitalizing on the complementary H bonding.     

Heterocirculenes as a new class of organic semiconductors

We report a fabrication of field-effect transistors using the new organic semiconductors octathio[8]circulene and tetrathiotetraseleno[8]circulene . The maximum hole mobility of 9 x 10(-3) cm(2) V(-1) s(-1) is, most likely, limited by one-dimensional growth of and in thin films.     

Arene–perfluoroarene interactions in crystal engineering. 5.

In the title complex, C₁₀F₈·C₆H₄S₄, planar centrosymmetric mol­ecules of tetra­thia­fulvalene and octa­fluoro­naphthalene, inclined to each other by 9.6 (1)°, form a mixed stack which does not exhibit charge transfer. Adjacent stacks pack in a herring-bone motif.     

Catalytic activity and mechanism for the action of pyridines in the phenolysis of epichlorohydrin

The reactivity of 3-chlorophenol with epichlorohydrin in the presence of substituted pyridines was studied. The reaction orders relative to the reagents and catalyst were determined. Correlations permitting evaluation of the effect of structure and concentration of the catalyst were obtained. The catalysis mechanism was found. Donetsk State University, 24 Universitetskaya ul., Donetsk 340055, Ukraine. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 35, No. 2, pp. 89–91, March–April, 1999.