Monitoring Photochemical Reactions in Single Crystals by X-ray Diffraction: Practical Aspects

Abstract

The influence of external stimuli on the decrease of crystal diffracting power and hence the quality of diffraction patterns and determined structures was studied in the case of the Norrish-Yang photochemical reaction of methyl 2-{[4-(2,4,6-triisopropylbenzoyl)benzoyl]amino}-3-phenylpropanoate, compound 1. The reaction was conducted in a single-crystal-to-single-crystal homogeneous manner. The calculated rate constant at 75°C was 1.6 9 10 -3 s -1 . In a quantitative way we illustrated a relationship between the reduction of the crystal diffracting power and the content of reactant molecules in the crystal and quantitatively showed that reactant molecules are responsible for this reduction. We observed that there is no correlation between the energy of UV-vis radiation applied to induce the photochemical reaction and the degree of the decrease of crystal diffracting power. We also showed in the case of the studied crystals that some change in temperature does not influence the degree of the decrease of the crystal diffracting power under the influence of UV-vis radiation. The unknown structures of the crystals containing pure reactant and product for compound 1 were also presented. Graphical AbstractThe influence of different external stimuli on the reduction of diffracting power of crystals was monitored quantitatively during and after the NorrishYang photochemical reaction.

The role of free space in photochemical reactions in crystals at high pressure – the case of 9-methylanthracene

“…The void volume and the distance between reactive atoms are two opposite geometric factors influencing the reaction rate of 1. The acceleration of reactions in crystals with increasing pressure was observed for the [2+2] photodimerization of 2,6-difluorocinnamic acid, 2,5-difluorocinnamic acid, 3,5-difluorocinnamic acid and 5-benzylidene-2benzylcyclopentanone (Galica, Ba ˛kowicz, Konieczny & Turowska-Tyrk, 2016;Galica et al, 2018;, but in the case of the Norrish-Yang reaction of 4-(2,4,6-triisopropylbenzoyl)benzoate benzylammonium and the salt of 6,6-diethyl-5-oxo-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid with (1S)-1-(4methylphenyl)ethylamine a decrease in the reaction rate was stated (Konieczny et al, 2015(Konieczny et al, , 2016, indicating that the phenomenon depends on the type and demands of a reaction. The X-ray structure analysis for 1 revealed the completeness of the reaction after 30 and 20 h of irradiation at 0.1 and 0.4 GPa, respectively, indicating a higher reaction rate at 0.4 GPa than at 0.1 GPa (Fig.…”

Monitoring photo-induced population dynamics in metastable linkage isomer crystals: a crystallographic kinetic study of [Pd(Bu4dien)NO2]BPh4

“…Table 1 lists the fitted initial and final MS occupations and kinetic parameters for the datasets, and fits obtained without fixed n are shown in the ESI † for comparison. We also note that, although there is precedent for modelling photo-excitation curves with JMAK kinetics, [25][26][27][28] is effectively equivalent to the simple exponential fitting function…”

Monitoring photo-induced transformations in crystals of 2,6-difluorocinnamic acid under ambient conditions

“…In general, UV radiation can cause two phenomena in crystals. The first is disintegration of the crystals and this process is characterized by a general decrease of the intensities of reflections (Konieczny et al, 2016;Turowska-Tyrk, 2003). The second phenomenon is connected with changes in the molecular and crystal structures brought about by a photochemical reaction and can also be observed by changes in the intensities and positions of reflections.…”

“…In order to conduct a reaction in a bulk of crystals, the applied wavelengths should come from the low-energy absorption tail (Enkelmann et al, 1993;Novak et al, 1993). However, in our experience, the application of such wavelengths does not necessarily ensure that a reaction will proceed homogeneously in the whole volume of the crystal and several other conditions should be fulfilled as well (Konieczny et al, 2016).…”