Synthesis and properties of thallium(III) porphyrin chelates

Bis-thallium(I) porphyrin complexes

“…3(A)) which introduces asymmetry [5]. Our X-ray study of Tl(III) porphyrin complexes showed the geometry about the Tl atom to be square-pyramidal [6,7].…”

“…There is no evidence to establish the existence of the monothallium(I) complex though they may be intermediates in the metalation process; the mono-thallium(I) species, if it exists, must have a very short lifetime. It should be noted that the method of choice for demetalation of thallium(III) complexes of porphyrins is first to reduce them to thallium(I) by using sulfur dioxide, then to add acid [5]. This further establishes the fact that the stability toward acid of thallium(III) complexes is much higher than that of thallium(I) complexes.…”

“…It was also found that the thallium(III) porphyrin chelates were oxidized by thallium trifluoroacetate in the presence of trifluoroacetic acid [4]. Later, detailed studies of thallium(III) porphyrin chelates were also reported [5], and it was shown that the proposed aqua-hydroxides (3) were obtained directly when porphyrins were metalated with thallium(III) nitrate trihydrate. Subsequent work [6] showed that the axial ligand on the thallium atom is chloride (i.e.…”

Synthesis and characterization of halogeno- and pseudo-halogeno-thallium(III) porphyrin complexes. Variation of the co-ordination geometry as a function of the axial ligand

“…The 13C NMR spectroscopy of thallium porphyrins has been investigated in detail by Abraham et al 26 The electronic absorption spectra (see Experimental section) show the two-banded spectra typical of many metalloporphyrins, as already noted in many publications on thallium(Ir1) porphyrins. 22 The complete halogeno series presented here allows however some conclusions with regard to the influence of different axial ligands on the properties and stability of the central metal atom. No drastic influence of different axial ligands on the wavelength of the main absorption bands is observed although there is a trend towards higher wavelengths with increasing size of the halogen atom.…”

“…The azide ligand is almost linear with an N-N-N angles of 176.4(9)0 in [Tl(tmpp)(N,)] and 176.7( 12)" in [Tl(tpp)(N,)].The TI-N(porphyrin)-N,, system deviates from a perfect square-pyramidal co-ordination. The smallest such angle is 102.0(2)0 for N( l)-Tl-N(24) in [Tl(tpp)(N,)] while the largest is 1 15.3(2)O for N( l)-Tl-N(22). In [Tl(tmpp)(N,)] these angles are 99.1(2) and 117.8(2)", respectively.…”