Carbon Cationic Relay via Superelectrophiles: Synthesis of Spiro‑diazafluorenes

Superelectrophilic-initiated carbon cationic relay reactions of diazafluorenones with phenols were developed to provide strategically novel and atom-economic access to spirodiazafluorenes via tandem Friedel–Crafts reaction, nucleophilic addition, and intramolecular cyclization sequences. A range of spirodiazafluorenes that are difficult to synthesize with traditional protocols has been constructed successfully in middle to high yields using this method

Structure–Property Study on Two New D–A Type Materials Comprising Pyridazine Moiety and the OLED Application as Host

In this paper, two new pyridazine based donor–acceptor type materials, i.e., 3CzPyaPy: 9,9′-(3-(6-(9H-carbazol-9-yl)­pyridazin-3-yl)­pyridine-2,6-diyl)­bis­(9H-carbazole) and 4CzPyPyaPy: 3,6-bis­(2,6-di­(9H-carbazol-9-yl)­pyridin-3-yl)­pyridazine, were synthesized with high yields. These two materials exhibited strong absorption/emission with high molar extinction coefficients and moderate photoluminescence quantum yield. The glass transition temperature of 3CzPyaPy was detected to be as high as 131 °C, showing its high thermal stability. Although the absorption energies and oxidation/reduction behaviors of the two materials were similar, the emission from 4CzPyPyaPy with longer effective-conjugation length presented hypsochromic shift both in films and in dilute solutions, contradicting to the common sense. The single crystal structure study disclosed their different space stretching and packing: 3CzPyaPy was twisted in larger angles and adopted dimerlike packing, while 4CzPyPyaPy showed smaller torsion angles and exhibited slipped herringbone packing. The dimerlike packing in 3CzPyaPy is responsible for its bathochromic shift of emission in solid state, while its unsymmetrical molecular structure accounts for that in solution. We believe that the unsymmetrical molecular structure of 3CzPyaPy is partially responsible for its high thermal-stability and also responsible for its HOMO dispersion which renders it slightly more difficult to oxidize. 3CzPyaPy was proved to be a bipolar-transport material and when served as a phosphor host, a green phosphorescent device achieved maximum efficiencies of 54.0 cd A^–1, 42.4 lm W^–1, and 17.7%, which are among the best with nonoptimized device structure, demonstrating its great potential for optoelectronic application. Furthermore, the new synthesized pyridazine derivatives and the corresponding structural and molecular-packing influences on material properties give a new insight into molecule tailoring

Organic Nanosynthesis of Ancient Windmill-like Window Gridarenes at Molecular Scale

We focus on another kind of square-type unit nanogrids with starlike divergent extensibility. As a result, square windmill-like nanogrid <b>WG4</b> have been successfully synthesized by two different kinds of fluorene-based nanosynthons, namely I-shape nanosynthon and L-shape nanosynthon synthesis method. Besides <b>WG4</b>, triangle and hexagon windmill-like nanogrids (<b>WG3</b> and <b>WG5</b>) are also obtained via one-pot nanosynthesis of I-shape nanosynthon with <b>WG3</b> as the main product. For the L-shape nanosynthon synthetic method, the cyclization process possesses higher selectivity, resulting to an excellent yield for <b>WG</b>4. In addition, two stereoisomers of the triangle nanogrids, <i>cis-trans</i>-<b>WG3</b> and <i>cis-cis-</i><b>WG3</b>, were separated and characterized from the single-crystal X-ray diffraction and ¹H NMR analyses for getting insight into the configuration of the triangle nanogrids with the skeleton planarization for the <i>trans</i>-configuration and deplanarization for the <i>cis</i>-configuration

Steric-Hindrance-Functionalized Polydiarylfluorenes: Conformational Behavior, Stabilized Blue Electroluminescence, and Efficient Amplified Spontaneous Emission

Control of the hierarchical molecular organization of polydiarylfluorenes by synthetic strategies is significant for optimizing photophysical properties as well as the performance of light-emitting devices. Herein, for the suppression of molecular aggregation and enhancement of luminescence efficiency, a series of steric units were introduced into polydiarylfluorenes by copolymerization, with the aim of integrating the advantages of the steric-hindrance effect and of the β-phase. Optical and Raman spectroscopies revealed a β-phase conformation for a polymer copolymerized with spiro­[fluorene-9,9′-xanthene] (SFX), with photoluminescence (PL) peaks at 454, 482, and 517 nm. Moreover, the morphological stability and electroluminescence (EL) stability were also improved without compromising the performance of the polymer light-emitting diodes (PLEDs). Furthermore, three steric-hindrance-functionalized copolymers showed significantly decreased thresholds for amplified spontaneous emission (<i>E</i>_th^ASE) and enhanced stability following thermal annealing treatment. These results indicate that steric-hindrance functionalization is a superior approach to improve the overall stability and optoelectronic properties for blue-light-emitting π-conjugated polymers