Tetramethoxy‐Aminorhodamine (TMARh): A Bichromophore, an Improved Fluorophore, and a pH Switch

Abstract

Rhodamine is one of the most widely used fluorescent dyes. Here, a new synthetic pathway to the popular dyes is reported and the effect of adding four methoxy groups to the molecular structure is investigated. Tetramethoxy-aminorhodamine (TMARh) is found to show superior pH switching compared to the rhodamine without the four methoxy groups, owing to changed properties of the dark "off" state and increased fluorescence intensity in the protonated "on" state.

Revealing the sensing mechanism of a fluorescent pH probe based on a bichromophore approach

“…11 The bichromophore model was further applied to methoxysubstituted ARh: tetramethoxy-aminorhodamine (TMARh), in which the xanthenium and phenyl groups are in a higher twist angle due to the steric demand of the four methoxy substituents. 9 In this case, two well-resolved absorption bands are clearly observed in the absorption spectrum (Fig. 1(b)): an intense absorption band with an absorption coefficient of B100 000 M À1 cm À1 centered at approximately 540 nm (Fig.…”

“…2 Fluorescent probes responds to these specific substances with a change of the fluorescence intensity (quenching or enhancing), color and/or lifetime. [3][4][5][6][7][8][9][10] A large number of different fluorescent probes and responsive molecules have been developed and still continue to emerge increasingly every year. 8,11 However, most of the studies focus on the synthetic aspects of new fluorescent probes or improved sensing performance, while the more fundamental studies addressing their sensing mechanism, especially their photophysics and excited-state dynamics, are limited.…”

“…In this bichromophore model, an arylpyrylium chromophore is identified as a part of the probe integrated with and perpendicular to the rhodamine chromophore. 9,11 In this model, fluorescence quenching is ascribed to the efficient internal conversion between the overlapping rhodamine and arylpyrylium states and fast structural relaxation of the arylpyrylium S 1 state to a dark low energy conformation. 11 The bichromophore model was further applied to methoxysubstituted ARh: tetramethoxy-aminorhodamine (TMARh), in which the xanthenium and phenyl groups are in a higher twist angle due to the steric demand of the four methoxy substituents.…”

Optical Chemical Sensor Using Intensity Ratiometric Fluorescence Signals for Fast and Reliable pH Determination

“…The first generation of optical pH sensors has been commercially available for some time . These report the pH of a solution using frequency domain determination of fluorescence lifetime, reflectance, and dye absorption. − Nevertheless, it seems that current optical pH sensor technologies are not acceptable to the industry. − The industry requires robust optical pH sensors to replace conventional pH electrodes in single-use bioproduction and stem cell culture, and for monitoring extended biopharmaceutical processes. − The competition from the familiar pH electrode has been too strong, and despite numerous reports on new fluorescent probes with promising sensor properties, − the progress in development of real sensors is slow …”

Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes

“…4, inset). This bichromophoric behavior has been studied in detail for the dialkylamino-substituted xanthenium/rhodamine system [45–46], and is also the likely reason for these compounds being non-fluorescent.…”