The distortion of the square pyramidal CoPcH4(CO) geometry on the SWCNT is likely due to strong spin-orbit coupling in the d 7 configuration . The 4-coordinate planar Co (II) ion has degenerate dxz and dyz orbitals which lie below the singly occupied dxy. Upon binding to the SWCNT, the Co distorts out of the N basal plane, swapping the dxz and dyz orbitals with the dxy orbital, so that dxy becomes doubly occupied lying below the doubly occupied dxz and singly occupied dyz.