Predicting wavelength-dependent photochemical reactivity and selectivity

Abstract

Predicting the conversion and selectivity of a photochemical experiment is a conceptually different challenge compared to thermally induced reactivity. Photochemical transformations do not currently have the same level of generalized analytical treatment due to the nature of light interaction with a photoreactive substrate. Herein, we bridge this critical gap by introducing a framework for the quantitative prediction of the time-dependent progress of photoreactions via common LEDs. A wavelength and concentration dependent reaction quantum yield map of a model photoligation, i.e., the reaction of thioether o-methylbenzaldehydes via o-quinodimethanes with N-ethylmaleimide, is initially determined with a tunable laser system. Combined with experimental parameters, the data are employed to predict LED-light induced conversion through a wavelength-resolved numerical simulation. The model is validated with experiments at varied wavelengths. Importantly, a second algorithm allows the assessment of competing photoreactions and enables the facile design of λ-orthogonal ligation systems based on substituted o-methylbenzaldehydes.

Action Plots in Action: In-Depth Insights into Photochemical Reactivity

“…Molar extinction spectra (solid curves, left axis) and adjusted action plot yields (symbols, right axis) of various photothermal cascade reactions. For ease of comparison, percentage yields were adapted from the literature ,,,, and normalized by the number of photoreactive units in solution and the number of photons delivered to the sample to give adjusted % yields. The inset highlights the region of low absorption.…”

Laser Photodissociation Action Spectroscopy for the Wavelength-Dependent Evaluation of Photoligation Reactions

“…33,35−37 While the action plot approach is undoubtedly insightful for comparing and contrasting absorption profile with reaction yield, 37−39 these experiments are time-consuming, rely on high-purity materials, and require careful control of photon count in situ to obtain accurate and comparable conversion values or quantum yields. 40 However, predicting the reactivity of a candidate tetrazole toward a dipolarophile requires more information than can be provided solely by absorption spectroscopy. Herein, UV photodissociation action spectroscopy (PDAS) is employed on an ion-trap mass spectrometer coupled to a tunable laser system to evaluate the wavelength dependence of nitrile imine formation from substituted tetrazoles.…”

“…While the action plot approach is undoubtedly insightful for comparing and contrasting absorption profile with reaction yield, − these experiments are time-consuming, rely on high-purity materials, and require careful control of photon count in situ to obtain accurate and comparable conversion values or quantum yields . However, predicting the reactivity of a candidate tetrazole toward a dipolarophile requires more information than can be provided solely by absorption spectroscopy.…”

DNA Walkers for Biosensing Development

“…It is well‐known that photochemical reaction is initiated by absorbing energy from light. [ 70 , 71 , 72 , 73 ] In 2012, Tan and his team designed a DNA walker that was capable of initiating, moving, and stopping with the control of light ( Figure 3 a ). [ 66 ] DNA walkers powered by light energy could be terminated at a desired position or time, and could be restarted easily.…”