The crystal structures of two cyanines dyes with the same aromatic core as C8S3, but different substituents (namely C2C2 32 and C8O3 33 ) were simulated to evaluate the performance of the QM generated parameters. The unit cell of each crystal is presented in Figure and 2d. To prepare the initial structure for the simulations, the unit cells for C2C2 and C8O3 were replicated along each dimension by a factor of 3, resulting in supercells consisting of 27 unit cells and 108 cyanine dye molecules. C2C2 crystal structures also included 108 iodine molecules to neutralise the charge and 216 methanol molecules, whereas C8O3 crystal structures included 54 dimethyl-sulfoxide (DMSO) molecules and no counter ions. Our goal was to find the best set of parameters that is able to maintain the experimental determined structures and, then, use it as reference for the CG model. The atomistic parameters were evaluated based on their ability to maintain structural features of the initial unit cells, such as box dimensions and density. The results from the crystal simulations are reported in Table of the Supplementary Information.