Stereochemistry of a Porphyrin Atropisomer. The Molecular and Crystal Structure of Six-Coordinate [5α,10β-bis(o-nicotinamidophenyl)-15,20-diphenylporphinato]zinc(II)

The synthesis and molecular structure of the title complex was investigated as part of our work into the chemical significance of atropisomerism in porphyrin compounds. The complex crystallizes in the triclinic system, space group P1, a=11.707 (2) Å, b=12.744 (5) Å, c=9.521 (2) Å, α=102.60 (3)°, β=101.31 (2)°, and γ=100.29 (2)°, Z=1. A total of 3737 reflections (average of two forms) were considered observed and used in the solution and refinement of the structure. The structure was refined to a final R=0.081. The molecule, with a crystallographically imposed inversion center, has disordered nicotinamide side chains. This disorder leads to some ambiguity in defining the relative substitution pattern of the phenyl rings. Independent of the assumptions used to define the disorder, the nicotinamide side chains are found to coordinate the zinc ions of adjacent molecules to form a polymeric, linear chain containing six-coordinate zinc ions. The average equatorial Zn–N bond distance is 2.052 (3) Å and the unique axial bond distance is 2.432 (5) Å.