Sessler and coworkers have explored the chemistry of many expanded porphyrins, among those amethyrin (model: 'amethyrin') which contains 6 pyrrole rings as two methine-bridged tripyrrole 'halves' and D2h ideal symmetry. The structure of the protonated form (NENBIR) is obviously non-planar -distorting by B2g, or 'monkey-saddle' C2h shape, at 9.5 Å. A Zn complex of a similar amethyrin (SURXIM) is only distorted 7 Å, whereas the Cu2Cl2 chelate of this ligand (ZUBGEI) is distorted by Au, B1u and B1g to approx. 10 Å each, resulting in a near-C2 twisted-and-bent shape.