MOLECULAR-STRUCTURE OF MESO-TETRA(4-PYRIDYL)PORPHYRINATOTHALLIUM(III)ACETATE, TL(TPYP)(OAC)

The molecular structure of meso-tetra(4-pyridyl)porphyrinatothallium(I II) acetate, Tl(tpyp)(OAc), has been determined by X-ray analysis. The displacement of the thallium atom from the porphyrin mean plane was 0 .858 Angstrom. The geometry around the thallium centre of the Tl(tpyp) (OAc) molecule has Tl-O(1) = 2.266(10), Tl-O(2) = 2.512(9) and average Tl-N = 2.224(8) Angstrom. This X-ray diffraction data provides eviden ce for an asymmetric pseudo-chelating acetato group coordinated to the thallium(III) atom. This might explain why intermolecular acetate exc hange is the chief exchange mechanism for Tl(tpyp)(OAc).