Most metalloporphenes, including Zn(II)P, belong to group 0, in which the number of π-electrons remains unperturbed by the presence of the metal. Therefore, all group 0 metalloporphenes have 26 π electrons per unit cell and display antiaromatic features. They can be divided further according to the extent of electron delocalization, or ascending U/t ratio: 0 tt (no Peierls distortion, gapless), 0 t (distorted, gapless), 0 U (antiaromatic semiconductors), and 0 UU (Baird aromatic semiconductors), as shown in Figure .