5,10-Diphenyl-15,20-di(4-methoxyphenyl)-21-telluraporphyrin (7) was prepared in 18% yield by the p-toluenesulfonic acid-catalyzed condensation of 2,5-bis(1-phenyl-1-hydroxymethyl)tellurophene (6), pyrrole, and 4-methoxybenzaldehyde in carefully deoxygenated CHCl3 followed by oxidation with p-chloranil. While H-1 and C-13 NMR spectra of 7 were consistent with a symmetrical molecule in solution, the X-ray crystal structure of 7 shows the pyrrole N-H on a pyrrole ring cis to the tellurophene and a planar porphryin core. Air oxidation of a CH2Cl2 solution of 7 under fluorescent lighting gave telluroxide 14. The reaction of a CH2Cl2 solution of 14 with 1 N HCl as a two-phase system gave 21,21-dichloro-21-telluraporphyrin 15. The X-ray structure of 15 indicated a distorted trigonal bipyramidal geometry around the Te atom with two chloride ligands occupying the axial positions. The Te atom and the N atom of the trans pyrrole were tipped out of plane in opposite directions to give a nonplanar porphyrin core. The Q-bands of the absorption spectra of 15 and vacataporphyrin 5 were similar, suggesting a similar aromatic structure in the two molecules.
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