1,2,5‐Triarylcycloalka[c]arsoles: Structural Effects of Fused‐cycloalkanes on Stability and Photophysical Properties

Abstract

Herein, we have synthesized a variety of cycloalkane-fused arsoles. Cyclopentane and cyclohexane were incorporated into the cycloalkane-fused arsoles. Surprisingly, cyclohexane-fused arsole 2 a gradually decomposed via oxidative ring-opening under ambient conditions, while cyclopentane-fused 1 a was stable. In addition, the Stokes shift of 2 a (7766 cm À 1 ) is larger than that of 1 a (5120 cm À 1 ).The effects of the fused cycloalkane on the stability and photophysical properties were attributed to the distortion of the cycloalkane. Computational calculations demonstrated that the cyclohexane moiety in 2 a was frustrated upon being incorporated into the rigid arsole ring, while the cyclopentane moiety in 1 a was much less distorted.

1‐Phospha‐Butadienes and 1H‐Phospholes via Alkynylation of Acetylenic Phosphaalkenes

“…In line with that we have also crystallographically identified an oxidative decomposition product of this phosphole, in which the Mes*P=O moiety was eliminated and the P−C bonds were oxidized to ketones (see Supporting Information for structural information). Notably Naka and co‐workers recently reported a systematic study on that oxidative cleavage in arsoles, indicating that ring strain plays a significant role in the stability of these five‐membered heterocycles [27] . Although the phosphaalkene alkynylation product 10 b could not be identified during this reaction, these crystallographically identified products clearly support the idea that similar alkynylation must precede the cyclisation steps.…”

“…Notably Naka and coworkers recently reported a systematic study on that oxidative cleavage in arsoles, indicating that ring strain plays a significant role in the stability of these five-membered heterocycles. [27] Although the phosphaalkene alkynylation product 10 b could not be identified during this reaction, these crystallographically identified products clearly support the idea that similar alkynylation must precede the cyclisation steps.…”

Synthesis and Photophysical Properties of Heavier Pnictogen Complexes

“…Transmetallation of Zr(IV) using CuCl afforded copper derivatives, which on further treatment with PhAsI 2, afforded the desired compounds (71)(72) in moderate to good yields (Scheme 13). [94] Cyclopentane-fused arsole 71 a was found to be stable, whereas The groups at the 2,5-positions of the arsole ring have little effect on the photophysical properties in solution. According to DFT calculations, the frustration of the fused cyclohexane in 72 a in the S 0 state was alleviated upon photoexcitation, leading to a considerable structural relaxation, which resulted in a bigger Stokes shift than that of 71 a.…”

“…Transmetallation of Zr(IV) using CuCl afforded copper derivatives, which on further treatment with PhAsI 2, afforded the desired compounds ( 71 – 72 ) in moderate to good yields (Scheme 13). [94] Cyclopentane‐fused arsole 71 a was found to be stable, whereas cyclohexane‐fused arsole 72 a gradually undergoes oxidative ring‐opening at room temperature. Depending on the 3,4‐substituents, arsole rings can have different conformations.…”

“…In order to understand the effect of pnictogen atoms on the characteristics of π-conjugated molecules, Naka and Imoto groups systematically investigated reactivity, coordination capabilities, and photo-luminescence properties of pnictogen-fused heterofluorenes (93)(94)(95)(96)(97). The reaction of PhECl 2 (E = Sb, Bi) with 2,2'-dilithiobiphenyl afforded Sb and Bi-fused heterofluorenes (96 and 97) in good yields (Scheme 19).…”