Diversity of Survey Set. Our aforementioned search criteria yielded 1007 distinct molecules crystallising in 1040 crystal structures observed in the CSD. The constraint of no rotatable bonds necessarily limits chemical diversity, but despite this our candidate set still displays a variety of chemical functionalities and molecular structures, as seen in Figure and Table . A complete list of molecules, including formulae, CSD refcode identifiers, SMILES strings, and systematic and common names is available in the Supporting Information.