Ruffling of Nickel(II) Octaethylporphyrin in Solution.

Nickel(II) octaethylporphyrin (NiOEP) plays a central role in studies of the molecular properties of tetrapyrroles and tetrapyrrole-containing enzymes. NiOEP in noncoordinating solvents is found to be a mixture of planar and nonplanar, ruffled species. At 77 K in frozen solutions, the S/sub 4/ ruffled form is more prominent than at room temperature. The ruffled form is most prominent for laser excitation to the red of the Soret absorption maximum, suggesting that the ruffled form has a red-shifted Soret band. The presence of multiple forms coexisting in solution requires that normal coordinate analyses based on NiOEP spectra be reexamined.