Figure also contains the results of respective TDDFT calculations. Overall TDDFT is in qualitative agreement with the present MS-RASPT2 results. As far as the coupling is concerned we observe a nonmonotonic shift between the two curves in Figure ; a more detailed analysis is provided in Fig. . This leads to a different behaviour of the excitonic energies in dependence on the Q y -shift in Figure , besides the overall shift of the monomer excitation energies (cf. Section S3.2).