No abstract

Herein we describe the structure–property relationships of three biazulene isomers (2,6′-biazulene (BAz1), 2,2′-biazulene (BAz2), and 6,6′-biazulene (BAz3)). The unimolecular planarities of these molecules follow the order BAz2 > BAz1 > BAz3, which is ascribable to the planar five-membered and the twisted seven-membered biaryl rings. This order is the same as the conjugation-expansion order, and the intramolecular reorganization energies show a similar trend. Hole mobility follows the order BAz2 > BAz3 > BAz1, where the lowest mobility of BAz1 is attributable to its asymmetric molecular orbital distribution. 2,2′-Binaphthalene (BNp), a structural isomer of biazulene, shows no field-effect transistor characteristics. Transfer integrals clearly support the observed superiority and inferiority of these hole-transport properties. This study demonstrates the crucial importance of both molecular structure and molecular orbital symmetries for charge transfer. The dimer approach involving the 2,6-positions of azulene generates linear structures due to the structural features of its five-membered and seven-membered rings. Hence, azulenes, which are relatively asymmetric from an aromatic perspective, exhibit high symmetries as their biazulene isomers. This is in contrast to the loss of symmetry when naphthalene is dimerized through its 2-position.

Exploration of pure metal-free organic molecules that exhibit strong room-temperature phosphorescence (RTP) is an emerging research topic. In this regard, unveiling the designp rinciples for an efficient RTP molecule is an essential,b ut challenging, task. As mall moleculei sa ni deal platformt op recisely understand the fundamental role of each functional component because the parent molecule can be easily derivatized. Here, the RTP behaviors of as eries of 3-pyridylcarbazole derivatives are presented. Experimental studies in combinationw itht heoretical calculations reveal the crucial role of the no rbital on the centralp yridine ring in the dramatic enhancemento ft he intersystem crossing between the charge-transfer-excited singlet state and the lo-cally excited triplet states. Single-crystal X-ray crystallographic studies apparently indicate that both the pyridine ring and fluorine atom contribute to the enhancemento ft he RTP because of the restricted motion owing to weak CÀH···N and H···F hydrogen-bonding interactions. The singlec rystal of the fluorine-substituted derivatives hows an ultra-long phosphorescent lifetime( t P )o f1 .1 sa nd ap hosphorescence quantum yield (F P )o f1.2 %, whereast he bromine-substituted derivative exhibits t P of 0.15 sw ith a F P of 7.9 %. We believe that this work providesafundamentala nd universal guideline for the generation of pure organic molecules exhibiting strongR TP.[a] Prof.

The partial fluorination of polycyclic aromatic hydrocarbons often produces a layered crystal packing, where fluorinated aromatic surfaces are stacked over nonfluorinated aromatic surfaces. Herein, we report the synthesis and crystal packing of partially fluorinated [4]helicenes with steric congestion resulting from H and F atoms in the fjord region. F 6 -[4]Helicene forms head-to-tail columnar stacks consisting of an alternate arrangement of perfluorinated and nonfluorinated naphthalene moieties. With decreasing fluorine content, aromatic stacking switched from areneÀ fluoroarene (Ar H À Ar F ) hetero-stacking to Ar H À Ar H / Ar F À Ar F homo-stacking with the help of intermolecular CÀ H···F contacts in the fjord region. As a result, head-to-head columnar stacks appear. Therefore, the conventional Ar H À Ar F stacking motif is not always applicable to F n -[4]helicenes with twisted π-surfaces.

A process for extracting vanadium from ammonia slag is proposed in this work, taking advantage of the nature of V 5+ vanadate ions condensing into a solid phase around a pH of 2. The slag is a mixture of oxides of Ca (36.0 mass %), Si (28.4 mass %), Al (9.3 mass %), Fe (7.1 mass %), V (6.9 mass %), S (3.9 mass %), Na (2.7 mass %), Ni (2.5 mass %), Mg (1.3 mass %), and other (K, P, and Ti) (1.9 mass %). The difficulty with extraction originates from the oxyanionic character of the vanadate ions, leading to the formation of vanadate salts with the concomitant cations. In contrast, a stepwise-pH-control process that is proposed in this work is effective for separating vanadium from the slag, as (1) the Si component in the slag is filtered off as the residue at the initial leaching step; (2) Fe, Al, and other cations are precipitated as the vanadate salts at pH 6, leaving Ca 2+ (aq) in the solution; (3) the vanadate component is transferred to the liquid phase by dissolving the precipitate in a NaOH(aq) solution of pH 13, leaving Fe, Ti, and Ni ions in the solid phase; and finally, (4) the pH of the solution is adjusted to 2. The vanadium component is solidified as sodium vanadate and V 2 O 5. The maximum yield of vanadium from the slag is evaluated as 80.7%, obtaining for NaV 6 O 15 and V 2 O 5 with a purity of 97 mass %.