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The synthesis, reactivity and full characterization of a series of meso-tetraalkyl porphyrins and metalloporphyrins with R ≡ n-butyl (6), 2-methyl-propyl (7), isopropyl (8), l-ethyl-propyl (10) and tert-butyl (11) groups are reported. Derivatives of the last of these show considerably bathochromically shifted absorption bands and the crystal structure of Zn(II)11(pyr) exhibits a severely ruffled macrocycle conformation. Systematic crystallographic studies of the porphyrins showed that the free base porphyrins with R ≡ n-butyl (H₂6), 2-methyl-propyl (H₂7) and 1-ethyl-propyl (H₂10) are planar. A larger conformational variety was found for the metal complexes. While most Ni(II) derivatives and Pd(II)₈ showed a ruffled macrocycle conformation with a degree of ruffling exceeding that of meso-unsubstituted porphyrins, both planar and non-planar forms were found for the related Cu(II) derivatives. The Zn(II) complexes of porphyrins with isopropyl or 1-ethyl-propyl exhibited conformations with variable degree of distortion. Together with comparative structures from the literature, this study provides experimental evidence that considerable conformational flexibility exists for meso-alkylporphyrins with substituents less bulky than tert-butyl groups.

The crystal structure of the triflate salt of the title compound, [Me₃TPP][CF₃SO₃], was investigated to obtain structural information on the conformation of N-trimethylated 5,10,15,20-tetraarylporphyrins. The molecular stereochemistry of the cation is characterized by an up/down/up arrangement for the three N-methyl groups with significant pyramidalization at the nitrogen atoms. The macrocycle is severely distorted with an average deviation from planarity of 0.438 Å. The distortion mode is an asymmetric saddle with deviations from the 4N plane of the C_b atoms at N-methylated pyrrole rings exceeding 1.1 Å. The out-of-plane displacements of pyrrole ring IV are significantly smaller than those of the methylated pyrrole rings.