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The texaphyrins are a novel class of pentadentate, porphyrin-like aromatic macrocyclic ligands that form kinetically stable complexes with essentially all cations of the trivalent lanthanide series. This ability, combined with certain features inherent to the texaphyrin skeleton, gives rise to species that are of potential interest in a range of medical applications including diagnosis and therapy. In this paper, the biomedical utility of one particular metallotexaphyrin derivative, namely the lutetium(III) complex PCI-0123 (1), is highlighted. This system generates singlet oxygen in 11% quantum yield in water (20–30% in organic solvents) and is an effective sensitizer for photodynamic cancer therapy as judged from animal model studies. It is currently in Phase I human clinical trials.

The synthesis and characterization of several lanthanide(III) texaphyrin complexes of 4, 5, 9, 24-tetraethyl-16, 17-dimethoxy-10, 23-dimethyl-13, 20, 25, 26, 27-pentaazapentacyclo[20.2.1.1 heptacosa]-1, 3, 5, 7, 9, 11(27),-12, 14, 16, 18, 20, 22(25), 23-tridecaene (2), 4, 5, 9, 24-tetraethyl-16, 17-bis((3-hydroxypropyl)oxy)-10, 23-dimethyl-13, 20, 25, 26, 27-pentaazapentacyclo-[20.2.1.1] heptacosa-1,3, 5, 7, 9, 11(27), 12, 14(19), 15, 17, 20, 22(25),-20, 25, 26, 27-pentaazapentacyclo[20.2.1.1] heptacosa-1,3, 5, 7, 9, 11(27), 12, 14, 16, 18, 20, 22(25), 23-tridecaene (30), respectively, are reported. Single crystals suitable for X-ray diffraction were obtained for the La(III) complex 3, the Gd(III) complexes 9 and 37, the Eu(III) complex 36, and the Lu(III) complex 22, by dissolving the respective complex in MeOH/CHCl[sub 3] and layering with diethyl ether. The five lanthanide(III) texaphyrin complexes all crystallize in the triclinic space group, P[bar 1] (No. 2), with Z = 2. The complexes are characterized by five-coordination from the texaphyrin, a coordinated methanol molecule on one side and at least one symmetrically bidenate NO[sub 3][sup [minus]] ion opposite the methanol. The 10-coordinate La(III) complex 3 has two bidentate NO[sub 3][sup [minus]] ions on the same side of the macrocycle. The europium(III) and gadolinium(III) texaphyrins 36 and 37 are structurally isomorphous and are 9-coordinate species with a bidentatemore » NO[sub 3][sup [minus]] ion and a methanol molecule on the top side of the macrocycle. On the other hand, the lutetium(III) texaphyrin is 8-coordinate with only a single bidentate NO[sub 3][sup [minus]] ion chelated on the [open quotes]top[close quotes] side of complex. In an unusual case of disorder, the gadolinium(III) texaphyrin 9 has both 9- and 10-coordinate species present in the solid state. The geometry of the 9-coordinate species is like that found in 36 and 37, while the 10-coordinate Gd(III) species similar to the La(III) species 3.« less

UV-vis absorption and magnetic circular dichroism (MCD) are reported for a series of metal salts of hexaalkyltexaphyrins, recently synthesized novel porphyrinoid structures. The results are interpreted in terms of the standard perimeter model. It is found that texaphyrin is a soft MCD chromophore and that the arrangement or frontier orbitals in metallohexaalkyltexaphyrins is, s, a, − s, − a in order or increasing energy

The syntheses of three new cadmium(II)-containing tripyrroledimethine-derived, ''texaphyrin''-type, macrocycles, 14,15-dicyano-4,5,9,20-tetraethyl-10,19-dimethyl-13,16,21,22,23- pentazatetracyclo[16.2 .1.13,6.18,11]tricosa-1,3,5,7,9,11(23)12,14,16,18(21),19-undecaene (1), 4,5,9,28-tetraethyl-10,27-dimethyl-13,24,29,30,31- pentaazahexaacyclo$B24.2.1.13,6. 18,11.014,23.016,21]-hentriaconta-1,,5,7,9,11(31),12,14(23),15,17,19, 21,24,26(29),27-pentadecaene (2), and 4,5,9,32-tetraethyl-10,31-dimethyl-13,28,33,34,35- pentaazaheptacyclo$B28.2.1.13,6. 18,11.014,27.015,20.021,26]pentariconta-1,3,5,7,9,11(35),12,14( 27),15(20),16,18,21(26),22,24,28,30(33,31-heptadecaene (3), are discussed. These compounds, which contain extended (pi) -systems, possess strong, low-energy, Q-like absorption bands in the 650-900 nm spectral region, making them of possible interest in photodynamic applications. Time-resolved absorption and emission laser studies have been carried out and the fluorescence and triplet absorption spectra, excited state yields and lifetimes, O2-quenching rate constants, and quantum yields for formation of O2(1(Delta) g) measured and related to the structure of the macrocycle. The results of preliminary cell localization and in vitro photodynamic anti-viral, anti-bacterial, and anti-leukemic cell inactivation studies carried out with these and/or the parent (omicron) -phenylenediamine-derived parent texaphyrin system, 4, are also presented.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Cadmium texaphyrin, [(TXP)Cd] + , a representative of a new family of expanded porphyrins, has an absorption maximum around 760 nm in acetonitrile solution. The first excited triplet state, which is formed with a quantum yield of 0.9, is quenched by O 2 , via an energy-transfer process, and by aromatic amines, via an electron-transfer reaction. This latter process produces [(TXP)Cd] o , the neutral radical, as characterized by flash photolysis methods, with an overall quantum efficiency of about 60%. The potential of the texaphyrin family as photosensitizers for photodynamic therapy is highlighted.