Synthesis of Azulene Derivatives That Have an Azathiacrown Ether Moiety and Their Selective Color Reaction Towards Silver Ions

Abstract

Azulene derivatives that have an azathiacrown ether moiety were synthesized by using a modification of the method described by Vögtle and co‐workers. These compounds are highly selective for detecting Ag+ ions, which is demonstrated visually by a color change from orange to violet. Structural studies of the Ag+‐induced colored product by NMR spectroscopy and ESI‐MS identified a 1:1 (Ag+:ligand) complex formed by the coordination of Ag+ ion with the azathiacrown ether moiety. Competition experiments in the presence of other metal ions, ESI MS/MS experiments on the Ag+ and Hg2+ complexes, and DFT calculations on the Ag+ complex suggest that the high selectivity and color change for Ag+ ion is due to the relatively strong binding of the azathiacrown ether moiety to Ag+ ion, and not to π–cation interactions. Azulene derivatives that are highly selective toward a particular heavy metal ion and undergo a distinct color change have not been reported before.

A Colorimetric Chemosensor Based on a Nozoe Azulene That Detects Fluoride in Aqueous/Alcoholic Media

“…This fact has been exploited for its use in a range of colorimetric sensors. Examples include sensors for silver (Wakabayashi et al, 2013), nitrite (Murfin et al, 2020), mercury (Wakabayashi et al, 2007(Wakabayashi et al, , 2008(Wakabayashi et al, , 2012Razus et al, 2011;Birzan et al, 2017;Buica et al, 2018Buica et al, , 2019, phosphate (Lichosyt et al, 2016(Lichosyt et al, , 2018, and reactive oxygen species (Murfin et al, 2019).…”

Development of Heterocycle-Substituted and Fused Azulenes in the Last Decade (2010–2020)

“…Similar to the aforementioned reaction, the reaction of 6-bromoazulene 146 with two ester groups with amines yields the corresponding 6-aminoazulene derivatives 147 in good to excellent yields ( Scheme 49 ) [ 68 , 69 ]. The electrophilic substitution reaction of a derivative with a pyrrolidine substituent at the 6-position with bromine provides 2-bromo-6-pyrrolidinylazulene derivative 148 .…”

Azulene—A Bright Core for Sensing and Imaging

“…Whilst the azulene core has been incorporated into a wide variety of colorimetric chemical probes (exploiting the vivid colours it is famous for) [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 ], this review will focus on those published probes that exploit the fluorescent nature of azulene. The nature of azulene fluorescence is highly dependent on substitution around the azulene core, which affects whether emission is more dominant from the S 2 or S 1 singlet excited state (a notable exception from this can be found in the work of Zhu et al, who showed that emission of azulene aldehydes can occur from the S 3 or S 2 excited state dependent on the nature of the hydrogen bonding present [ 31 , 32 ]).…”