Peraryl Arsoles: Practical Synthesis, Electronic Structures, and Solid-State Emission Behaviors

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 (lambda(em)=445 nm) gave amorphous samples with a greenish-blue emission (lambda(em)=496 nm).