Xanthene derived dyes are known to be efficient fluorescent dyes. Generally speaking, functional groups on the conjugated moiety of the dye (chromophore) have the ability to fine tune the dye's fluorescent colors and so is the case with, more specifically, xanthenes. For instance, fluorescein is a green emitting fluorescent compound that has an emission peak at 515 nm, whereas the anionic dye of eosin that can be regarded as the brominated fluorescein, emits at 544 nm—a significant bathochromic shift.
Some xanthene derived dyes consist of the Rhodamine dyes. These compounds can be regarded as diaminated analogs of xanthene (at the positions 6′ and 3′; see below for further elaboration on the numbering convention of rhodamine) which has been additionally arylated at the 9′ position. Rhodamines fluoresce and have been used extensively in research, both as free dye and as conjugates to larger molecules, e.g. proteins and antibodies as biomarkers.
Rhodamines are outstanding versatile organic dyes. They demonstrate thermal and photochemical stability, strongly absorb visible light, and show high fluorescence quantum yields. Rhodamine based compounds have been utilized as industrial dyes, electronic materials, medical devices, bio markers, lighting devices, sensors and photovoltaics. Within the rhodamine family of compounds, one of the commonly used fluorescent rhodamine dye is rhodamine 6G which has high quantum yield and high photostability, rendering it a suitable compound in optical and electro optical applications, as well as biotechnological applications. This example of rhodamine 6G along with other ones such as, for example sulforhodamine 101 and rhodamine 101 show that there is a significant need in the dyes and pigments industry for the synthesis of new fluorescent dyes with superior optical and electro optical parameters such as fluorescence intensity, quantum yield and photostability. Said synthetic compounds form the basis of numerous novel (bio)optical and (bio) electro-optical devices.
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