Rhodamine B is a fluorescent dye based on a xanthene core that can be used as a staining reagent a biomarker or the basis of fluorescent sensors for pH changes and metal ions. Rhodamine B exhibits dynamic activity as the form it adopts depends on the acidity or basicity of its environment, which in turn impacts the fluorescent properties it exhibits. Under basic conditions, Rhodamine B is in the closed form with little conjugation and so it exhibits a low level of fluorescence. In an acidic environment, Rhodamine B is in its opened form and is highly conjugated, resulting in maximum fluorescence, due to its opened form. We are interested in how the creation of Rhodamine B dimers may impact the optical properties of this dye. We have synthesized a rigid dimer of Rhodamine B using a benzene linker and have confirmed its structure with ultraviolet-visible spectroscopy (UV-vis), liquid chromatography-mass spectrometry (LCMS), and nuclear magnetic resonance (NMR). We have found that the extraction and purification processes impact whether the opened or closed forms of the Rhodamine B rigid dimer is isolated. We have optimized these procedures to be able to isolate either form with high purity.

Isolating the opened and closed forms of a rigid dimer of the cluorescent dy Rhodamine B

ACS Spring 2022

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