Please do not adjust margins Please do not adjust margins An advantage of using ΔEgap instead of the computed IR spectrum is that modes with no IR intensity (dD/dQi = 0) due to symmetry can also be IRAVs; indeed, some of the first IRAVs were observed in Raman-active modes. In case of 1 •+ the symmetric stretch of the butadiyne linker at 2156 cm -1 (see Figure and) is IR forbidden, but it is strongly coupled to the ground electronic state as it decreases the conjugation between the two porphyrins.