Rhodols - synthesis, photophysical properties and applications as fluorescent probes

The formal replacement of one dialkylamino group in rhodamines with a hydroxyl group transforms them into rhodols. This apparently minor difference is not as small as one may think; rhodamines belong to the cyanine family whereas rhodols belong to merocyanines. Discovered in the late 19th century, rhodols have only very recently begun to gain momentum in the field of advanced fluorescence imaging. This is in part due to the increased understanding of their photophysical properties, and new methods of synthesis. Rationalization of how the nature and arrangement of polar substituents around the core affect the photophysical properties of rhodols is now possible. The emergence of so-called π-expanded and heteroatom-modified rhodols has also allowed their fluorescence to be bathochromically shifted into regions applicable for biological imaging. This review serves to outline applicable synthetic strategies for the synthesis of rhodols, and to highlight important structure-property relationships. In the first part of this Review, various synthetic methods leading to rhodols are presented, followed by structural considerations and an overview of photophysical properties. The second part of this review is entirely devoted to the applications of rhodols as fluorescent reporters in biological imaging.

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A dual-mode turn-on fluorescent BODIPY-based probe for visualization of mercury ions in living cells

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A facile, fast responsive and highly selective mercury(ii) probe characterized by the fluorescence quenching of 2,9-dimethyl-1,10-phenanthroline and two new metal–organic frameworks

A fast responsive and highly selective mercury(ii) sensor was developed using the fluorescence quenching mechanism of 2,9-dimethyl-1,10-phenanthroline (2,9-DMP) towards mercury(ii).

Smart excimer fluorescence probe for visual detection, cell imaging and extraction of Hg2+

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