Solid-State Dilution of Dihydroxybenzophenones with 4,13-Diaza-18-crown-6 for Photocrystallographic Studies

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.