ROY Reclaims Its Crown: New Ways To Increase Polymorphic Diversity

Chemical compounds that exist in
multiple crystalline forms are
said to exhibit polymorphism. Polymorphs have the same composition,
but their structures and properties can vary markedly. In many fields,
conditions for crystallizing compounds of interest are screened exhaustively
to generate as many polymorphs as possible, from which the most advantageous
form can be selected. We report new ways to search for polymorphs
and increase polymorphic diversity, based on crystallization induced
by suitably designed mixed-crystal seeds. The potential of the strategy
has been demonstrated by using it to produce new polymorphs of the
benchmark compound ROY as single crystals structurally characterized
by X-ray diffraction. This allows ROY to reclaim its crown as the
most polymorphic compound in the Cambridge Structural Database. More
generally, the methods promise to become valuable tools for polymorphic
screening in all fields where crystalline solids are used.