A Versatile Approach for In Situ Monitoring of Photoswitches and Photopolymerizations

Abstract

A simple, inexpensive, and modular method to directly illuminate NMR samples for in situ analysis of photochemical transformations is reported. The versatility of this technique is demonstrated by analyzing the light‐induced propagating front for small‐molecule photoswitches and the kinetics of photocontrolled living radical polymerizations. In situ measurements allow oxygen‐sensitive and rapid photoevents to be studied in detail, leading to reliable determination of photoswitching quantum yields and polymerization rates. By systematically tuning light intensity, a direct relationship between propagation rate and intensity is revealed. Of particular note is the facile translation of the conditions identified through this NMR analysis to analogous benchtop experiments with insight into the nature of the photoreactive species.

A versatile method for the determination of photochemical quantum yields via online UV-Vis spectroscopy

“…Furthermore, quantitative analysis may require error prone dilution steps and long measurement times. Recently, alternative approaches for the determination of photo-dissociation quantum yields have been introduced, based on NMR techniques, 16 laser-flash photolysis (LFP) 17 and peak-height analysis of size exclusion chromatography (SEC) traces after pulsed-laser polymerization (PLP). 18 However, the lack of a "standardized" procedure makes it difficult to compare the quantum-yield values obtained from different methods.…”

Level of Theory and Solvent Effects on DASA Absorption Properties Prediction: Comparing TD-DFT, CASPT2 and NEVPT2

“…It is remarkable that in only a few years, a considerable number of applications have been reported for DASA derivatives, including polymer science [ 16 , 17 , 18 , 19 ], targeted drug release [ 20 , 21 ], temperature localization [ 22 ], energy storage [ 23 ], the monitorization of photochemical transformations [ 24 ] and orthogonal photoswitching [ 18 , 25 ]. The breadth of applications is due to the versatility of this photochrome, as well as its outstanding properties: high molar absorptivity, photoswitching under visible light, and easy synthetic access [ 13 , 14 ].…”

Speeding up NMR by in Situ Photo‐Induced Reversible Acceleration of T1‐Relaxation (PIRAT)

“…Before the next scan/increment, the spin switch is reverted to its “silent” ( S= 0) state with blue light. Several setups for in situ irradiation of samples inside NMR spectrometers have been reported in the recent time and are continuously optimized.…”

“…During the pulse sequence and data acquisition (indicated by black boxes and FID) the spin switch rests in its diamagnetic state ((E)-1, S = 0), and is paramagnetic ((Z)-1, S = 1) duringt he relaxation delay.with blue light. Severals etups for in situ irradiation of samples inside NMR spectrometers have been reported in the recent time [22][23][24][25][26] and are continuouslyoptimized.The principle behind our approachi si llustrated in Figure 2, where we follow the z-magnetization recovery after the final 908 pulse(black rectangle) of ap ulses equence. Theblue curve represents the z-magnetization of asample containing diamagnetic (E)-1.…”

“…with blue light. Severals etups for in situ irradiation of samples inside NMR spectrometers have been reported in the recent time [22][23][24][25][26] and are continuouslyoptimized.…”