. Furthermore, we find that the energy difference between the C i and C 2 conformers is negligible (see Table , ESI) indicating that both, along with other conformers, should be present at room temperature. To obtain consistent results, we select C 2 conformers for all subsequent calculations, unless specified explicitly. Optimised ground-state geometries, considering the C 2 case, are presented in Fig. and the geometric data for C 2 and C i are shown in Table . Generally speaking, we find significant twisting for both torsion angles considered. Starting with the discussion of the C 2 geometries, the Cz/Ph twisting angles (θ 1 /θ 1 ) are consistently ≈57 • for both molecules. By comparison, the twisting around the Ph/core junction (θ 2 /θ 2 ) is notably reduced owing to reduced steric hindrance. Twisting in Cz-AQ is larger than in Cz-BDT (39 • vs 26 • ) which can be understood by considering that the AQ group has two hydrogen atoms in the vicinity of the Ph group whereas BDT only has one. Cz-BDT is, thus, expected to allow for enhanced conjugation between the Ph and BDT groups and we will explore the consequences of this on the observed photophysics in more detail below. Proceeding to the bond distances, we find that the Cz-Ph distances (d 1 /d 1 ) are very similar for both molecules (≈ 1.417 Å). For the d 2 /d 2 values however, the bond distance is shorter in Cz-BDT (1.479 Å) than Cz-AQ (1.491 Å) following the same trends as expected for the bond angles, i.e. conjugation is stronger for Cz-BDT. Table also presents results for the C i geometry as well as data from previous work on the two molecules 4,29 using the B3LYP functional. The observed trends between the three data sets are consistent indicating that these geometric parameters are fairly robust with respect to both the precise conformer studied and the functional chosen.