51750-83-5Relevant academic research and scientific papers
Study of Rhodamine-Based Fluorescent Probes for Organic Radical Intermediates
He, Jiaxin,Yan, Boyu,Meng, Jiangtao,Ran, Maogang,Zhou, Yutong,Deng, Jinfei,Li, Chao-Jun,Yao, Qiuli
, p. 4059 - 4064 (2021)
Rhodamine-based amide derivatives for the detection of radical intermediates in organic reactions were synthesized and used as fluorescent probes over a wide range of solvents. The mechanistic studies confirm a reversible opening and closing of the spirolactam ring. Compound 21 can be used to support the radical mechanism or in the real-time monitoring of radical intermediates.
Tuning the pKa of Fluorescent Rhodamine pH Probes through Substituent Effects
Stratton, Sarah G.,Taumoefolau, Grace H.,Purnell, Grace E.,Rasooly, Mona,Czaplyski, William L.,Harbron, Elizabeth J.
, p. 14064 - 14072 (2017)
Rhodamine spirolactams (RSLs) have recently emerged as popular fluorescent pH probes due to their fluorescence turn-on capability and ease of functionalization at the spirolactam nitrogen. Design of RSLs is often driven by biological targeting or compatibility concerns, rather than the pH sensitivity of the probe, and the relationship between RSL structure and pKa is not well understood. To elucidate the relationship between pKa values and the properties of substituents attached to the spirolactam nitrogen, a series of 19 aniline-derived RSLs is presented. RSLs derived from di-ortho-substituted anilines exhibit pKa tunability across the moderately acidic region (ca. pH 4–6). Evaluation of pKa data using the Fujita–Nishioka model for ortho substituent effects reveals that both steric and electronic substituent properties influence RSL pH responsiveness, with pKa values increasing as substituent size and electron withdrawing character increase. These trends are attributed to changes in the RSL structure induced by large substituents, and to electronic influences on the protonated spirocyclic reaction intermediate. To demonstrate the practical applicability of these probes in completely aqueous environments, RSL-doped conjugated polymer nanoparticles that exhibit a ratiometric fluorescence response to changing pH levels are presented.
Tuning the Photophysical Properties of Spirolactam Rhodamine Photoswitches
Li, Bo,Haris, Uroob,Aljowni, Maha,Nakatsuka, Andrew,Patel, Shreya K.,Lippert, Alexander R.
, p. 244 - 252 (2020/11/30)
Spirolactam rhodamines are fluorescent photoswitches that are useful for single molecule localization microscopy, volumetric 3D digital light photoactivatable dye displays, and other applications. Measurement of the photophysical properties, particularly photoswitching kinetics and quantum yields, is challenging and a comprehensive understanding of how molecular structure affects these parameters remains incomplete. In this study, we have synthesized a series of N-aryl spirolactam rhodamine photoswitches with fluorescent emissions at 585 nm and 518 nm. Extinction coefficients and fluorescence quantum yields of the fluorescent form of the photoswitch have been measured using excess trifluoroacetic acid to drive the equilibrium to the open form. A method to determine photoswitching kinetics and quantum yields was developed by monitoring the kinetics to reach equilibrium between the on-state and off-state and fitting this data to a rate equation for a reaction in equilibrium. Trends based on the electronic and steric properties of the aryl substituents were evaluated. Using this information, a proof-of-principle demonstration of 3D voxel formation was accomplished using a green (518 nm) emitting photoswitch, setting the foundation for a multi-colour volumetric 3D display.
