Ring Expansion of Spiro-thiolactam in Rhodamine Scaffold: Switching the Recognition Preference by Adding One Atom

Abstract

A new rhodamine spiro scaffold with a six-membered reactive ring was developed by inserting a nitrogen atom in the known probe rhodamine B spiro thiohydrazide, which switched the recognition preference of the probe from Hg(2+) to Cu(2+). This probe is shown to be an efficient "turn-on" fluorescent chemodosimeter for Cu(2+) in a neutral aqueous medium. Mechanism studies suggested that the probe opened its spiro-ring by a Cu(2+)-induced transformation of the cyclic thiosemicarbazide moiety to an isothiocyanate group.

Selectively sensing first-row transition metal ions through fluorescence enhancement

“…The rhodamine B based chemosensor 83 with a sixmembered reactive ring was developed by inserting a nitrogen atom in the known uorescent probe rhodamine B spiro thiohydrazide. 124 This sensor is shown to be an efficient "turn-on" uorescent chemodosimeter for Cu 2+ in a neutral aqueous medium due to opening of the spiro ring (Scheme 44). Other biologically relevant or heavy metal ions do not induce ringopened uorescence enhancement.…”

Detection and Removal of Metal Ion based on a Fluorescent Sensor Composed of a Photoresponsive Rhodamine Derivative by Host-Gust Interaction

“…Fluorescent spectrophotometry is an important technique to detect metal ions owing to its distinct advantage of facile detection, high sensitivity, and easy tenability . Among the fluorescent sensors, the rhodamine scaffold is an ideal template chromophore for the construction of metal chemosensors because they have large molar extinction coefficients, long excitation and emission wavelengths, and high fluorescence quantum yields . Moreover, rhodamine derivatives with a spirolactam structure are colorless and nonfluorescent, whereas those with a ring‐opened amide form give rise to both chromogenic and fluorogenic response to facilitate an OFF/ON‐type fluorescent detection .…”

Fabrication of novel chemosensors composed of rhodamine derivative for the detection of ferric ion and mechanism studies on the interaction between sensor and ferric ion

“…Rhodamine scaffold is an ideal template chromophore for the construction of chemosensors because they have large molar extinction coefficient, long excitation and emission wavelengths and high fluorescence quantum yields. 17,18 Moreover, rhodamine derivatives with a spirolactam structure are colorless and nonfluorescent, whereas a ring-opened amide form of rhodamine derivative gives rise to both a chromogenic and fluorogenic response to facilitate an OFF/ON-type fluorescent detection. Therefore, a number of fluorescence sensors have been developed based on rhodamine derivatives with different recognition groups for the detection of metal ions.…”