Acidic-sensing property of 9-(cycloheptatrienylidene)fluorene by UV-Vis spectroscopy

Color Change of Sudan III against Concentrated Sulfuric Acid in Acetonitrile and Quantification for a Small Amount of Concentrated Sulfuric Acid

“…For example, Wang et al investigated acid-sensing applications of 9-(cycloheptatrienylidene)fluorine in the range of 0 -4 M. 9 Our previous paper reported on an optical sensing method using Oil Red O supported by florisil, which enables one to predict the approximate concentration of sulfuric acid in the range of 0.5 -12 M by visual observation. 10 In our previous method, however, it is difficult to discriminate concentrations over 12 M; also, the mechanism for the color change of Oil Red O has not been understood.…”

Electron Transfer and Aggregate Formation Coinduced Emission Enhancement of 9-Cycloheptatrienylidene Fluorenes in the Presence of Cupric Chloride

“…With the addition of CuCl 2 into the THF solution of 3, significantly decreased absorption at 379 nm was detected (Figure S3), which was similar to its addition with acid. 16 However, no emission was observed for 3 before and after addition of Cu 2+ . Oxidative coupling of 1 afforded 4 in 80% yield (Scheme S1).…”

Fluorescent chemosensors based on 9-cycloheptatrienylidene fluorenes (9-CHFs)

“…17 In fact, the acidification process of 9-CHF could be tracked and measured by an UV-vis spectrophotometer. 36 As a result of the gradual addition of concentrated sulfuric acid or concentrated hydrochloric acid, two new bands at 267 nm and 230 nm were observed with the appearance of three clear isosbestic points at 316 nm, 258 nm, 235 nm (Scheme 4). During the process of acidification, 1 was protonated to form cation 2 in 99% conversion when the concentration of sulfuric acid reached 3.73 M. This result indicated that the absorption of 1 varied with the acidity and might serve as a potential pH-sensor under strongly acidic conditions.…”