Red–orange–yellow reclaims polymorph record with help from molecular cousin

A compound nicknamed Roy (red–orange–yellow) has – again – claimed the record as the molecule with the most polymorphs, now 10 in total.

Roy, or 5-methyl-2-[(2-nitrophenyl)-amino]thiophene-3-carbonitrile, is a precursor to the antipsychotic drug olanzapine and named after its colourful crystal forms. For decades, it has been a favourite of crystallographers as it has more than four polymorphs – one of only 0.001% of compounds among the million in the Cambridge Structural Database to have this property.