Synthesis of Silicon-Bridged Benzocrown Ethers and Their Ionochromism in the Emission Spectra Arising from Intramolecular π−π Stacking

Abstract

Compounds having two benzocrown ether units bridged by a mono-, di-, or trisilanylene unit were prepared, and ionochromic effects on their optical properties were studied. Of these, disilanylene- and trisilanylene-bridged ones exhibited clear ionochromism in the emission spectra and the intensity of the original emission band at about 320 nm decreased and a new broad band centered at 400 nm appeared when appropriate alkali or alkali-earth metal ions were added into the acetonitrile solutions. In contrast, a monosilanylene-bridged benzocrown ether and a disilanylbenzocrown ether showed ionochromic changes in different fashions, indicating that the new emission band at low energy of the di- and trisilanylene-bridged benzocrown ethers in the presence of metal ions may be ascribed to the intramolecular π−π stacking. MO calculations were carried out to understand the ionochromism.

Preparation of Poly(silylene-p-phenylene)s Bearing a Benzo Crown Pendant Group and Their Iono- and Solvatochromic Behavior in the Emission Spectra

“…Here, we report the synthesis and iono- and solvatochromic behaviors of poly(silylene- p -phenylene)s having a benzo crown ether group as the pendant group, which is anticipated to interact with metal ions more tightly than linear ether side chains. In these polymers, electron-donating silyl substitution on the benzo crown unit would even facilitate the coordination to the metal ions . As expected, the polymers exhibited clear ionochromism in the emission spectra toward selected alkali-metal and alkaline-earth-metal ions, depending on the ring size of the crown ether.…”

“…Recently, we found that disilanylene- and trisilanylene-bridged benzo crown derivatives shown in Chart exhibited ionochromic behaviors responding to alkali and alkaline-earth- metals . However, in contrast to the present polymers, the silanylene-bridged benzo crown derivatives showed the emission maximum at about 320 nm in the absence of metal ions; addition of metal ions to the solutions led to a decrease of the emission intensity of the original band, together with enhancement of a new broad band centered at 400 nm.…”

Selective Formation and SHG Intensity of Noncentrosymmetric and Centrosymmetric 1,1,2,2-Tetramethyl-1-(4-(N,N-dimethylamino)phenyl)-2-(2′-cyanophenyl)disilane Crystals under External Stimuli

“…Recently, investigation of oligosilyl derivatives represents a significant challenge to understand the photophysical properties due to the effective σ–π conjugation through Si–Si bonds. − Especially, diaryldisilanes are promising as soft crystals driven from the conformational variety and flexibility of Si–Si σ-bonds. Previously, we reported that the donor–acceptor disilane 1 (Figure ) displayed second harmonic generation (SHG) in the crystalline state, which is widely used in advanced photonic technologies. − This compound has a strong transition dipolar moment by a strong donor moiety (−NMe 2 ) and an acceptor moiety (−CN) with Si–Si σ-conjugated linker, showing no absorption in the visible light region different from a large π-extended skeleton.…”