Homoadamantane-Fused Tetrahydroquinoxaline as a Robust Electron-Donating Unit for High-Performance Asymmetric NIR Rhodamine Development

Abstract

Rhodamines have emerged as a useful class of dye for bioimaging. However, intrinsic issues such as short emission wavelengths and small Stokes shifts limit their widespread applications in living systems. By taking advantage of the homoadamantane-fused tetrahydroquinoxaline (HFT) moiety as an electron donor, we developed a new class of asymmetric NIR rhodamine dyes, NNR1−7. These new dyes retained ideal photophysical properties from the classical rhodamine scaffold and showed large Stokes shifts (>80 nm) with improved chemo/photostability. We found that NNR1−7 specifically target cellular mitochondria with superior photobleaching resistance and improved tolerance for cell fixation compared to commercial mitochondria trackers. Based on NNR4, a novel NIR pH sensor (NNR4M) was also constructed and successfully applied for real-time monitoring of variations in lysosomal pH. We envision this design strategy would find broad applications in the development of highly stable NIR dyes with a large Stokes shift.

De Novo Design of a Highly Stable Ratiometric Probe for Long-Term Continuous Imaging of Endogenous HClO Burst

“…First, a series of photostable dyes, HFTCs, were judiciously designed based on the following considerations: (1) a classical coumarin platform was selected as the matrix for novel photostable dye construction due to their excellent photophysical parameters such as high fluorescence quantum yield, relatively large Stokes shift, and sufficient chemo/photostability; 36 (2) tetrahydroquinoxaline was employed as the electron-donating group due to their incomparable electron-donating capability, thereby significantly intensifying the intramolecular charge transfer (ICT) process of the target coumarin dyes, giving longer emission wavelength and larger Stokes shift; 37 and (3) a large steric hindrance homoadamantane moiety was embedded with tetrahydroquinoxaline to act as a shielding unit to ensure high stability of the target coumarin dyes; a strategy was already verified in our previous work. 35 Second, with these dye candidates in hand, their photophysical properties, especially the related photostability, will be studied, and the most suitable dye scaffold with excellent photostability will be screened out. Finally, based on the selected dye platform, various probes equipped with distinct HClO-identifying sites will be constructed.…”

Comparison of Polarization Energies from B3LYP and MP2 Parameterizations: Spherical Benzene and Anthracene Clusters

“…Organic small molecule (OSM) based materials have been widely used in many applications, such as in the fields of energy [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and sensing, [19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36] due to their abundance and versatility of functionalization that makes systematically tuning device performance feasible. As such, studies of organic small molecules have become a very active research field ranging from designing special functionalities, studying the excited state properties of OSMs, [58][59][60][61][62][63][64][65][66][67][68][69]…”