Solid-state dilution of dihydroxybenzophenones with 4,13-diaza-18-crown-6 for photocrystallographic studies

Abstract

This work forms part of the ongoing drive toward identifying and developing suitable light sensitive substances for photocrystallographic studies. In order to investigate the solid-state dilution of the photoactive dihydroxybenzophenone, X-ray crystal structures of three dihydroxybenzophenone•4,13-diaza-18-crown-6 co-crystals are reported and analyzed. The dihydroxybenzophenone molecules within the co-crystal are compared to those observed in homomolecular dihydroxybenzophenone crystals in terms of their intermolecular contacts, bond geometry and conformation. Molecular volumes and void spaces were calculated using Voronoi-Dirichlet polyhedra and Hirshfeld surface-based space partitioning, demonstrating new ways to represent potential reaction cavities around a photoactive molecule and calculate their packing efficiency. In each case the conditions of solid-state dilution were met. The molecular conformations of the homomolecular environments are retained to varying degrees in the analogous co-crystals. Results show that the co-crystals studied are potentially suitable for photocrystallography. In particular, 2,4-dihydroxybenzophenone molecules in 4,13-diaza-18-crown-6•2(2,4- dihydroxybenzophenone) co-crystals exhibit high structural similarity to their homomolecular analogues suggesting its photochemical properties could be common to both environments. © 2012 American Chemical Society.