Spectral Properties of Fluorogenic Thiophene‐derived Triarylmethane Dyes

Abstract

Spectral properties and fluorogenic behaviors of five novel thiophene variants of Malachite Green (MG), termed MGTs, were determined. Appreciable changes as a function of homologation and substitution pattern, including absorption band positions and intensities and fluorescence quantum yields were observed. In particular, the shorter wavelength y-band absorption was found to shift over a nearly 200 nm range based on aryl group variation, allowing fine-tuning of the excitation wavelength for these dyes. In addition, the fluorescence intensity of some MGTs increased significantly (up to 4,600-fold) when the dye was bound to a cognate protein partner, which is potentially useful for cell imaging studies.

Heterolytic Bond Cleavage in a Scissile Triarylmethane Mechanophore

“…This supports the scissile heterolytic cleavage and formation of Tr + triggered by mechanical activation, ruling out the unlikely, yet computationally possible, cleavage of the C 1 –C 2 bond (Figure a). Indeed, the two bands at 444 and 630 nm are the characteristic x and y bands of Tr + and are associated with the polarization of the π electron density across the rings mediated by the aromatic substituents (morpholine moieties in this case) and the resonance across the orthogonal, pendant (styrenyl) ring, respectively . Previous investigations of malachite green, which is structurally similar to Tr-1 , revealed that the main absorption band of the malachite green radical is at 400 nm. , The radical decomposes rapidly (within tenths of microseconds) into the malachite green carbocation, as reflected by the development of two absorption bands with maxima around 430 and 620 nm. , The striking similarity of these spectra with the ones shown in Figure b supports the conclusion that, in the present system, the color is indeed produced by the Tr + species, although it is impossible to discern if a radical is transiently produced.…”

“…Indeed, the two bands at 444 and 630 nm are the characteristic x and y bands of Tr + and are associated with the polarization of the π electron density across the rings mediated by the aromatic substituents (morpholine moieties in this case) and the resonance across the orthogonal, pendant (styrenyl) ring, respectively. 44 Previous investigations of malachite green, which is structurally similar to Tr-1, revealed that the main absorption band of the malachite green radical is at 400 nm. 45,46 The radical decomposes rapidly (within tenths of microseconds) into the malachite green carbocation, as reflected by the development of two absorption bands with maxima around 430 and 620 nm.…”

Engineering Glowing Chemogenetic Hybrids for Spying on Cells

“…The use of electrondonating thiophene aryl groups has permitted to extend the spectral properties of FAP:MG analogs to the red. [79] Introduction of electron-donating groups on the aromatic ring of HBR analogs allowed the design of FAST fluorogens with red-shifted absorption and emission properties for applications in multicolor imaging. [80] The ability to change color by fluorogen exchange allowed dynamic color switching in cells, providing a unique kinetic signature that could be advantageously exploited for highly multiplexed imaging.…”

Fluorogen-Activating Proteins: Next-Generation Fluorescence Probes for Biological Research

“…74 Chemical modifications of a Malachite-Green (MG) fluorogen derivative with thiophene aryl groups results in multiple red-shifted fluorescence emissions. 75 This tuning of fluorescence is dependent on the electron-donating thiophene rings that increase stability of the central carbenium ion. 75 Thus, chemical alterations of cell impermeable TO-and MG-fluorogens yield analog variants with alternate FAP fluorescence emissions.…”

“…75 This tuning of fluorescence is dependent on the electron-donating thiophene rings that increase stability of the central carbenium ion. 75 Thus, chemical alterations of cell impermeable TO-and MG-fluorogens yield analog variants with alternate FAP fluorescence emissions.…”