A set of flexible π-conjugated hydrocarbon molecules was generated by successively applying a series of molecular transformation operations to benzene (see Fig. ), similar to the procedure used in ref. [30]. At each step, these operations modify structural elements in the parent molecule or add additional ones. The set of operations used herein includes biphenyl-conjugation, annelation (5/6-ring) and ring-contraction, among others (see SI for details). Based on these transformations, molecular structures with up to four rings and two linker atoms were randomly generated, leading to 131.810 unique structures. This set forms the virtual screening space for this study. DFT calculations were performed for a subset of 10.900 structures (see below).