Emissive Photoconversion Products of an Amino-triangulenium Dye

Abstract

Upon prolonged exposure to intense blue light, the tris(diethylamino)-trioxatriangulenium (A3-TOTA(+)) fluorophore can undergo a photochemical reaction to form either a blue-shifted or a red-shifted fluorescent photoproduct. The formation of the latter depends on the amount of oxygen present during the photoconversion. The A3-TOTA(+) fluorophore is structurally similar to rhodamine, with peripheral amino groups on a cationic aromatic system. The photoconversion products were identified by UV-vis absorption and steady-state and time-resolved fluorescence spectroscopy, and further characterized by HPLC, LC-MS, and (1)H NMR. Two reaction pathways were identified: a dealkylation reaction and an oxidation leading to formation of one or more amide groups on the peripheral donor groups. The photoconversion is controlled by the experimental conditions, in particular the presence of oxygen and water, and the choice of solvent. The results highlight the need to characterize the formation of fluorescent photoproducts of commonly used fluorescent probes, since these could give rise to false positives in multicolor/multilabel imaging, colocalization studies, and FRET based assays. Finally, an improved understanding of the photochemical reaction leading to bleaching of fluorescent dyes can lead to the creation of specific probes for fluorescence based monitoring of chemical reactions.

Fluorophore photostability and saturation in the hotspot of DNA origami nanoantennas

“…Further mechanistic studies are required to confirm the exact nature of these dim states, however, we propose that it might be related to the formation of spectrally-shifted emissive forms of the fluorophores. Such spectral shifts leading to the formation of blueand red-shifted emissive forms of fluorophores have previously been observed in single-molecule fluorescence studies of rhodamine [53,54], oxazine [53], cyanine [53], carbopyronine [5], terrylene diimide [55], and amino-triangulenium [56] dyes. The most extensive mechanistic studies of such spectral instabilities have been carried out for rhodamine class of dyes, where the spectral shift and formation of photo bluing products have been associated with N-dealkylation of tertiary amine groups which proceeds via formation of a radical cation [57,58].…”

Triarylmethane Fluorophores Resistant to Oxidative Photobluing

“…Similar reactivity was observed upon electrochemical or photocatalytic oxidation of tertiary amines. Formation of chemically stable photoredding products is much more uncommon; however photooxidation of an N , N -diethylamino substituent into the corresponding N -ethylacetamide imposing a spectral red shift has been demonstrated for a trioxatriangulenium dye . On the contrary, similar α-oxidation of the dialkylamine fragment of coumarin 153 resulted in regioisomeric amide photoproducts with blue-shifted absorption maxima …”

“…Formation of chemically stable photoredding products is much more uncommon; however photooxidation of an N,Ndiethylamino substituent into the corresponding N-ethylacetamide imposing a spectral red shift has been demonstrated for a trioxatriangulenium dye. 19 On the contrary, similar αoxidation of the dialkylamine fragment of coumarin 153 resulted in regioisomeric amide photoproducts with blueshifted absorption maxima. 20 Related to the oxidative photodealkylation process described above is the transition of a fluorophore into a twisted intramolecular charge transfer (TICT) excited state, which in the case of triarylmethane dyes corresponds to an internal electron transfer from a (di)alkylamino substituent to the xanthylium core.…”

Biosorption of Malachite Green, Safranine T and Methylene Blue onto Spent Substrate of Flammulina Velutiper

“…With the rapid development of dye industry and the widely use of dyes, there are about 10 percent to 15 percent of the dyes to be released into the environment, which results in the problem of dye wastewater pollution. The treatment methods of dye wastewater include mainly physical, chemical and biological methods [1][2]. In recent years, the agriculture and food industry waste, such as orange peel, sawdust, rice husk as a biosorbent for the removal of dye wastewater has attracted a lot of attention [3].…”