Metal Complexes of Dioxo-porphyrins-Zinc(II) Complexes of 2,3,7,8,12,13,17,18-Octaethyl-5,15-dioxo-porphyrin and 5,15-Dioxo-etioporphyrin I

The crystal structures of two zinc(II) 5,15-dioxo-porphyrins (porphodimethenes) have been determined to investigate the coordination chemistry of porphyrins with interrupted conjugation system. Both compounds have a five-coordinated zinc center with pyridine as axial ligand and show overall structural parameters very similar to porphyrins. The oxidized meso-positions are, however, easily identified by longer C_m–C_a bond lengths and smaller C_a–C_m–C_a angles. The macrocycles exhibit a small degree of conformational distortion, and the etioporphyrin I derivative shows evidence for π-stacking in the crystal. Crystal data: 1 – C₄₁H₄₇N₅O₂Zn. Triclinic, a = 10.052(3) Å, b = 14.139(4) Å, c = 14.635(5) Å, α = 105.17(2)°, β = 108.62(3)°, γ = 106.29(2)°, V = 1745.3(9) ų, CuKα radiation, λ = 1.54178 Å, space group P1̅, Z = 2. R = 0.089. 2 – C₃₇H₃₉N₅O₂Zn. Triclinic, a = 12.122(3) Å, b = 12.383(3) Å, c = 12.759(4) Å, α = 61.77(2)°, β = 72.19(2)°, γ = 70.32(2)°, V = 1563.8(8) ų, CuKa radiation, λ = 1.54178 A, space group PĪ, Z = 2, R = 0.076.