Of the two co-crystals, PYRPMA was found to be the easier landscape for locating structures. Despite the greater dimensionality of the search space, the latest of the space group global energy minima to be located in the pure QR search was in P 2 1 /c after 866 steps (Table ). Counts of the number of low energy structures located in each space group are presented in the Supporting Information (Table ). We also monitored the step at which the structure corresponding to the experimentally observed co-crystal structure was located. This was located as the 3 rd lowest energy structure in space group P 2 1 , 2 kJ mol -1 above the global minimum.