Synthesis, structures, and photophysical properties of π-extended arsaborins.

In this study, various (hetero)arene-fused arsaborins were synthesized. All the synthesized arsaborins were stable under ambient conditions and allowed for the chemical modification of the lone pair of the arsenic atom. Experimental and computational studies revealed that these compounds possessed planar structures and weak anti-aromatic properties. Fluorescence with large Stokes shifts was observed due to drastic structural relaxation at 298 K, whereas intense phosphorescence due to the heavy-atom effect of arsenic was observed at 77 K. Furthermore, a thiophene-fused derivative demonstrated a temperature-dependent emission color change in the solid state, attributable to the gradual alteration in the ratio of monomer fluorescence, excimer fluorescence, and phosphorescence.

Steric and electronic effects of arsa-Buchwald ligands on Suzuki-Miyaura coupling reaction.

The Suzuki-Miyaura coupling (SMC) reaction is one of the most commonly used cross-coupling reactions. Bulky biaryldialkyl monophosphine ligands, i.e., Buchwald ligands, are beneficial for the SMC reaction. We recently developed a synthetic procedure for arsa-Buchwald ligands, arsenic analogs of Buchwald ligands, and found that these ligands are effective for sterically hindered substrates because of facilitating the transmetalation step owing to the longer arsenic-palladium bond. However, the relationship between the structure and steric/electronic properties of the arsa-Buchwald ligands has not yet been studied in detail. In this study, a series of arsa-Buchwald ligands with various alkyl substituents were synthesized. The cyclopentyl group afforded the highest catalytic activity for the SMC reaction, particularly with sterically hindered substrates. Furthermore, the steric/electronic properties of the arsa-Buchwald ligands were computationally analyzed.

Synthetic Strategy for AB2-Type Arsines via Bidentate Dithiolate Leaving Groups.

Despite their potential for several transition-metal-catalyzed reactions, arsenic ligands are poorly diversified. In this work, we developed an efficient synthetic methodology for AB2-type ligands, which is a typical motif in phosphorus systems, for example, in Buchwald ligands. The introduction of 1,2-benzenedithiol to tribromoarsine reduces the reactivity of two of the three reaction sites. After the substitution reaction with the first nucleophile involving the elimination of bromide, the substitution reaction with the second nucleophile produced AB2-type arsines through the elimination of the dithiolate anion. Among the various types of obtained AB2-type arsines, the arsa-Buchwald ligands, which are arsenic analogues of Buchwald ligands, were applied to the Suzuki-Miyaura cross-coupling reaction. Some of the arsa-Buchwald ligands showed activity comparable to that of the well-known Buchwald ligand, SPhos. Furthermore, the arsenic analogue of SPhos showed higher activity and stability than SPhos under open-air conditions.

Tetrachlorocatecholates of triarylarsines as a novel class of Lewis acids.

Pnictogen-mediated Lewis acidity is an emerging research subject in organic chemistry, supramolecular chemistry, etc. In contrast to the extensive studies on phosphorus and antimony, the diversity of arsenic-Lewis acids was quite limited. Herein, tetrachlorocatecholates of triarylarsines were newly synthesized. Their structures, electronic properties, and Lewis acidities were experimentally and computationally examined and compared with the corresponding phosphorus and antimony analogs. This is the first systematic study on the relationship between the structure and Lewis acidity of arsenic-mediated Lewis acids.

Turn-on type sensing of methanol vapor by a luminescent platinum(II) dichloride complex with 21-dibenzoarsacrown-7.

The development of turn-on detection sensors for methanol vapor remains challenging in materials science. Methanol sensing materials are generally based on vapor-triggered color changes or are turn-off types. Additionally, in general, the selectivity for methanol is limited, and the recyclability is low. Turn-on type sensing, high selectivity, rapid response time, and recyclability are favorable for achieving real-time detection systems. Herein, platinum(ii) dihalide (PtX2, X = Cl, Br, and I) complexes with 21-dibenzoarsacrown-7 were synthesized and their structures were characterized by single-crystal diffraction analysis. The PtCl2 complex showed intense emission when capturing methanol molecules in the crystalline matrix. In addition, this sensing system possessed high selectivity for methanol vapor and required facile recycling procedures.

Synthesis and Characterization of Boron Difluoride Complexes Bearing π-Expanded Pyridine Ligands as Organic Fluorochromes.

Novel boron complexes bearing pyrrole and π-expanded pyridine structures, such as quinoline, isoquinoline, and phenanthridine, were prepared. These compounds showed the fluorescence emission characters in both solution and solid state. Particularly, several complexes in solution exhibited high fluorescence quantum yield with Stokes shift values being four to five times larger than that of boron dipyrromethenes (BODIPYs). The present paper describes the optical properties of these novel boron complexes as well as their halogenated derivatives from the results of both experimental and computational studies.

Dibenzoarsacrowns: an experimental and computational study on the coordination behaviors.

Dibenzoarsacrowns have been synthesized as a novel class of heteroatom-fused crown ethers. The dibenzoarsacrowns can size-selectively capture alkali metal cations, and the arsenic atoms chemoselectively coordinated to gold(i) chloride (AuCl) due to the soft Lewis acid-base interaction. It is notable that the AuCl complex of 21-dibenzoarsacrown-7 further encapsulated Na+ with the enhanced association constant from bare 21-dibenzoarsacrown-7. The positive allosteric effect was studied computationally.