PW91, and ωB97X-D3BJ 55 using pseudopotentials to treat the iodine atoms with either double or triple ζ basis sets. This is based on the widespread use of the DFT functionals within the field of computational chemistry. Furthermore, we study DKH-CCSD(T) and ZORA-CCSD(T) as possible scalar-relativistic benchmark values, and spin-orbit ZORA-B3LYP, spin-orbit ZORA-PBE0, and PBE0-4comp (full four component relativistic DFT), and as possible full-relativistic benchmark values. For the energies we studied the same DFT functionals using pseudo-potentials and coupled cluster calculations using either pseudopotentials or scalar-relativistic Hamiltonians, together with this we also tested the use of the DLPNO approximation in the form of DLPNO-CCSD(T 0 ) calculations. Unless otherwise specified, all DLPNO calculations use the tight PNO criteria.