Spirocyclic rhodamines are promising sensors that exhibit turn-on fluorescence response to different stimuli including electric potential. Although rhodamine B hydrazide is often used as a building block for chemical and electrochemical sensors, the electrochemistry of this compound has not been reported. Herein, the electrochemical transformations of rhodamine B hydrazide are investigated using a combination of spectroelectrochemistry, liquid chromatography/mass spectrometry, and fluorescence spectroscopy. Pure rhodamine B hydrazide is a spirocyclic compound that is neither colored nor fluorescent. The electrooxidation of rhodamine B hydrazide in acetonitrile is shown to produce rhodamine B, a phtalazinone derivative, and a phenanthrenone derivative. These compounds exhibit fluorescence bands peaked at 580, 645, and 770 nm, respectively. The electrooxidation mechanism probably involves diazo, diazonium, and acylium intermediates. These findings imply a variety of applications for rhodamine B hydrazide as an electric potential sensor.

中文翻译：

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罗丹明B酰肼的电氧化

螺环罗丹明是一种很有前途的传感器，它对包括电位在内的不同刺激表现出开启荧光响应。尽管罗丹明 B 酰肼经常用作化学和电化学传感器的构建模块，但该化合物的电化学性质尚未见报道。在此，结合光谱电化学、液相色谱/质谱和荧光光谱研究了罗丹明 B 酰肼的电化学转化。纯罗丹明 B 酰肼是一种螺环化合物，既不着色也不发出荧光。罗丹明 B 酰肼在乙腈中电氧化可生成罗丹明 B、邻苯二甲嗪酮衍生物和菲酮衍生物。这些化合物的荧光带峰值分别为 580、645 和 770 nm。电氧化机制可能涉及重氮、重氮和酰基中间体。这些发现意味着罗丹明 B 酰肼作为电位传感器具有多种应用。