As previously noted, the transition from H-to J-type coupling occurs at about 5.4 Å Q y -shift, which corresponds to θ ≈ 33 • (Figure ). This value is far from 54.7 • , which would be expected from the dipole approximation. This is due to the short Z-shift distance between the two monomers, which causes higher order multipoles to contribute to the coupling. Figure in the supporting information shows how the angle where the type of aggregate changes, depends on the Z-shift, approaching 54.7 • for larger distances. Furthermore, increasing the Z-shift also smooths out excitonic excitation energy changes along the in the Supporting Information.), approaching the situation where the two curves are symmetrical with respect to the monomer excitation energy, and permanent dipole effects disappear.