Basis sets including diffuse functions-aug-cc-pVTZ and def2-TZVPD-produce minima that are considerably lower than basis sets without diffuse functions, meaning that the absolute interaction energies are larger for both CC2 variants in those cases. As CC2 more greatly overestimates the interaction energy minima, additional diffuse functions give well depths furthest from the CCSDR(3) reference. Interestingly, def2-TZVPD produces a deeper minimum than aug-cc-pVTZ. For SCS-CC2, def2-TZVPD and aug-cc-pVTZ differ by 0.58 kcal/mol, while for CC2 they differ by 0.38 kcal/mol. Without diffuse functions, Dunning and Ahlrichs basis sets are closer in energy; for instance, def2-TZVP and cc-pVTZ minima differ by 0.19 kcal/mol and 0.24 kcal/mol for SCS-CC2 and CC2 respectively (Table † ). The choice to include diffuse functions is highly system and method dependent as in some cases their addition can increase the BSSE of the system. In the case of exciplex binding, diffuse functions giving a worse result may suggest that the BSSE and BSIE do not decrease at the same rate. The impact of diffuse functions is of interest for future studies. Herein, we choose to discard them for prag-matic reasons, as the CCSDR(3) data could not be obtained with diffuse functions. However, this decision will not influence our subsequent TD-DFT benchmark study, as long as the same type of basis set is used therein. Our final findings and conclusions are therefore unlikely to be affected by this decision.