Steering photochemical reactivity of 2,4,6-triisopropylbenzophenonate anion in a crystalline state

• The Norrish–Yang reaction in crystals was studied by X-ray structure analysis.
• The homogeneity of the reaction was analysed by the JMAK model.
• The crystal lattice was modified by introducing various counterions.
• The influence of different surroundings on molecules in crystals was analysed.
• It is possible to largely change reactivity of chemical species in crystals.

The Norrish–Yang reaction was conducted in crystals of benzylammonium, pyrrolidinium and ammonium 4-(2,4,6-triisopropylbenzoyl)benzoates (1–3). The crystal structures of 1–3, six structures of the partly reacted crystals of these compounds and the structure of the pure product crystal for 1 were determined. The content of the product in the partly reacted crystals allowed to calculate the values of the rate constants and the orders of the reaction for 1 and 3 by the JMAK model. The results indicated that the Norrish–Yang reaction proceeded homogeneously for 3 and according to a hybrid mechanism for 1. The rate constant was much higher for 3 than for 1. The differences in the reactivity were explained by the intramolecular geometrical parameters and intermolecular interactions mapped onto the Hirshfeld surfaces. The results showed that it is possible to largely change reactivity of the one organic species, even several hundred times, by modifying the crystal lattice in which it is embedded.

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