2,3,4,5-Tetraaryl-1-phenylarsoles were synthesized by utilizing safely generated diiodophenylarsine and zirconacyclopentadienes. The obtained peraryl arsoles showed aggregation-induced emission (AIE), where intense emission was observed in the solid states (quantum yields up to 0.61), whereas the corresponding solutions were very weakly emissive. The optical and electronic properties were examined by experimental and computational methods. It was elucidated that the aryl groups at the 2,5-positions affected the frontier orbitals and the aromaticity of the arsole core. On the other hand, those at the 1,3,5-positions were perpendicular to the luminophore and effective for a restriction of aggregation-caused quenching. Because the lone pair of the arsenic atom has a sufficient coordination ability due to the low aromaticity of the arsole moiety, a gold(I) chloride complex of 1,2,3,4,5-pentaphenylarsole was synthesized. The complex formation caused a blue shift of the emission from the bare ligand. Interestingly, the complex showed luminescent mechanochromism; grinding the crystals with a blue emission (λ =445 nm) gave amorphous samples with a greenish-blue emission (λ =496 nm).

[5]Radialene is known as an unstable cyclic hydrocarbon with a cross‐conjugated system. Incorporation of heteroatoms into [5]radialene skeleton is an effective strategy for stabilization. Herein we synthesized dithieno[3,4‐b:3',4'‐d]arsole (1) as a novel class of hetero[5]radialenes since trivalent arsenic atom is much more stable than phosphorus one, which was used for hetero[5]radialene but unstable in air. The characteristic nature of the arsa[5]radialene was experimentally and computationally studied by comparing with the isomer, dithieno[3,2‐b:2',3'‐d]arsole (2). Structural analysis by X‐ray crystallography and computational evaluation of aromaticity revealed the radialene character of 1. Interestingly, 1 showed phosphorescence though only fluorescence was observed for 2. Time‐dependent density functional theory (TD‐DFT) calculations implied that intersystem crossing could readily occur upon excitation for 1. Furthermore, it was computationally elucidated that dimerization and/or oligomerization via Diels‐Alder reaction, which convert [5]radialene, were circumvented to offer stability for 1.

No abstract

Herein, we synthesized pnictogen (P, As, Sb)‐ and chalcogen (O, S)‐containing diheteroanthracene derivatives with 8π‐electron systems. As opposed to the pnictogen atoms, the chalcogen atoms significantly affected the conformations of the diheteroanthracenes. In addition, the S‐containing compounds exhibited relatively large Stokes shifts owing to significant structural relaxations compared with those of the O‐containing compounds. Computational calculations revealed that the bent conformations of the S‐containing compounds in their ground states planarized upon photoexcitation.

The Front Cover shows characteristic features of (p‐(diphenylarsino)phenyl)diphenylphosphine, in which the phosphorus atom preferentially coordinates to Lewis acids such as borane and metals (Au and Pt). The tilted balances represent about its asymmetric coordination behavior. This kind of molecule can be utilized as a template ligand to precisely arrange various Lewis acids, particularly transition metals. More information can be found in the Full Paper by Hiroaki Imoto, Kensuke Naka et al.

Phosphorus and arsenic have different coordination ability to Lewis acids, though they belong to 15 group. Utilizing the difference, we designed a novel ligand, (p‐(diphenylarsino)phenyl)diphenylphosphine, in which diphenylphosphine and diphenylarsine units are combined through a p‐phenylene linker, as a template to arrange Lewis acids. The phosphorus atom exhibited superior coordination ability to the arsenic one. NMR studies revealed that BH3, AuCl, and PtCl2 were preferentially coordinated by the phosphorus atom. Sequential addition of these Lewis acids realized precise arrangement on the template ligand.

Pentaphenylarsole was synthesized in 1959, but a detailed investigation had not been performed. In this work, peraryl arsoles were synthesized by a practical synthetic route, in contrast to the conventional methods which require dangerous arsenic precursors. The image shows that the combination of experimental and computational studies has successfully elucidated the fascinating nature of the perarylarsoles. More information can be found in the Full Paper by K. Naka, et al. on page 8797.

The Front Cover shows characteristic features of dithieno[3,4‐b:3',4'‐d]arsole, which has been newly synthesized as a novel class of hetero[5]radialenes. It exhibited phosphorescence, while only fluorescence was observed for the isomer, dithieno[3,2‐b:2',3'‐d]arsole. In addition, the arsa[5]radialene had high stability under ambient condition unlikely to hydrocarbon‐only [5]radialene because the Diels–Alder dimerization/polymerization was circumvented. More information can be found in the Full Paper by H. Imoto, K. Naka et al.