Joan-Anton Farrera

Aggregation in water solutions of tetrasodium diprotonated meso-tetrakis(4-sulfonatophenyl)porphyrin

The title porphyrin shows non ideal cmc with formation of J-aggregates, due to the formation of intermolecularly stabilized zwitterions, which at high concentration also results in H-aggregates.

Stirring effects on the spontaneous formation of chirality in the homoassociation of diprotonated meso-tetraphenylsulfonato porphyrins.

Homoassociates of the achiral title porphyrins in acid solutions show spontaneous symmetry breaking, which can be detected by circular dichroism (CD). The CD spectra are due to differential scattering and differential absorption contributions, the relative significance of which is related to the shape and size of the homoassociate. When an earlier model, designed for the association of these diprotonated porphyrins (J aggregates with the geometry of stepped sheets of intramolecular-stabilised zwitterions), was applied to an exciton-coupling point-dipole approximation, the folding of the one-dimensional homoassociates explained the CD signals detected. An effect of the vortex direction, caused by stirring or rotary evaporation, upon the exciton chirality sign was detected. In the case of H2TPPS3, the number of experiments performed gave a statistical significance to this effect. This vortex effect can be attributed to enhancement of the chirality fluctuations that originate in the diffusion-limited aggregation to high-molecular-weight homoassociates. In this sense, the phenomenon could be general for supramolecular systems that are obtained under kinetic control, and its detection would be possible when inherent chiral chromophores were being generated in the association process.

SELF-ASSEMBLY IN WATER OF THE SODIUM SALTS OF MESO-SULFONATOPHENYL SUBSTITUTED PORPHYRINS

The aggregation in water of the free bases and the diprotonated forms of p-sulfonatophenyl and phenyl meso-substituted porphyrins [sodium salts of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4), 5,10,15-tris(4-sulfonatophenyl)-20-phenylporphyrin (TPPS3), 5,10-bis(4-sulfonatophenyl)-15,20-diphenylporphyrin (TPPS2A), 5,15-bis(4-sulfonatophenyl)-10,20-diphenylporphyrin (TPPS2O), 5-(4-sulfonatophenyl)-10,15,20-diphenylporphyrin (TPPS1) and 5,15-bis(4-sulfonatophenyl)porphine (DPPS2O)] was studied by UV/Vis, 1H-NMR, fluorescence, polarized fluorescence and resonance light scattering. The presence of hydrophobic phenyl groups favours the aggregation. The free bases TPPS4 and TPPS3 aggregate into stacks of ill-defined geometry. TPPS2A and DPPS2O give H-aggregates. TPPS2O and TPPS1 give J-aggregates through interaction of the hydrophobic phenyl groups, that is their geometry corresponds to edge-to-edge arrangements. All these porphyrins give J-aggregates upon diprotonation, through electrostatic interactions between the positively charged porphyrin ring and the sulfonato group. These J-aggregates give different arrays depending on the meso-substitution pattern.

Self-assembly of cyclodextrins with meso-tetrakis(4-sulfonatophenyl)porphyrin in aqueous solution

Abstract The ability of α-CD, β-CD and γ-CD to break the aggregates in the solution of the title porphyrin (TPPS4) and to form inclusion self-assemblies has been studied by UV/Vis and 1H-NMR (ROESY). The behaviour of TPPS4 in the presence of α-CD, β-CD and γ-CD has been compared to that of sodium p-toluenesulfonate and sodium benzenesulfonate. TPPS4 in neutral media forms inclusion assemblies, through its meso-phenyl groups, with β-CD and γ-CD, but not with α-CD. Diprotonated TPPS4, which has a different geometry from the free base, forms an inclusion assembly only with β-CD. The inclusion assemblies of TPPS4 with β-CD and γ-CD show different geometry: introduction of the phenyl substituent through the cyclodextrin secondary face for β-CD and through the primary face for γ-CD.

The antioxidant role of bile pigments evaluated by chemical tests

Bilirubin, biliverdin and their serum albumin complexes were tested as oxyradical scavengers (superoxide generated by the xanthine/xanthine oxidase system and peroxyl radical-trapping antioxidant ability). As superoxide scavengers the free bile pigments showed activities near to that of serum albumin, higher than the water soluble vitamin E analog Trolox and lower than ascorbic acid. The peroxyl radical-trapping antioxidant abilities of the tested bile pigments were much higher than those of the serum albumin and of the same order as their serum albumin complexes. This interaction with peroxyl radicals showed different stoichiometric factors for bilirubin (approximately 2) and biliverdin (approximately 4).

REACTIVITY OF PYRROLE PIGMENTS, XX. ON THE STRUCTURE OF CU(II) AND ZN(II) TRIPYRRIN-1-ONE CHELATES IN SOLUTION

SummaryThe Cu(II) and Zn(II) chelates of 12,14-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one, 12,13-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one, and their sulfonate derivatives are studied. The chelates show the expected structure of an NH dideprotonated ligand chelating the metal ion. However, in the case of the Zn chelate of 12,14-dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-one the ligand is only monodeprotonated, and the lactam ring is tautomerized to a hydroximino function.ZusammenfassungDie Cu(II)- und Zn(II)-Chelate von 12,14-Dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-on, 12,13-Dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-on und ihrer Sulfonate wurden untersucht. Erwartungsgemäß findet man einen NH-dideprotonotierten Liganden im Chelat; im Zn-Complex von 12,14-Dimethyl-2,3,7,8-tetraethyl-15H-tripyrrin-1-on ist der Ligand nur einfach deprotoniert, und das Lactam ist zur Hydroximinogruppe tautomerisiert.

Self-assembly to ordered films of the homoassociate solutions of the tetrasodium salt of 5,10,15,20-tetrakis(4-sulfonatophenyl) porphyrin dihydrochloride

Abstract Films were obtained from the evaporation on flat glass substrates of homoassociate water solutions of the title porphyrin. The films of 1 were characterized by UV–VIS and FT-IR spectroscopy, microscopy, X-ray diffraction, thermogravimetry (TG) and differential scanning calorimetry (DSC). The films are composed by a birefrigent organic phase and NaCl crystallites; the organic phase shows an orientated structure. The water content of the film depends directly on the water-vapour pressure of the surrounding atmosphere; a change of structure occurs for pH2O>10 Torr and there is a transition to gel-like material for pH2O>20 Torr. In the organic phase, water, sodium, and chloride ions are placed in layers or channels parallel to the evaporation surface with thickness depending on the water content.

Reactivity of pyrrole pigments: Part 14. The electrochemical oxidation and reduction of bile pigments

Abstract The anodic oxidation of dipyrrin-1(10 H )-ones, biladiene- ac -diones (bilirubins), bilindiones (biliverdins), two 2,3-dihydrobilindiones and phycocyanobilin dimethyl ester were studied by cyclic voltammetry in N,N -dimethylformamide. The cathodic reduction of the bilindiones, the 2,3-dihydrobilindiones and phycocyanobilin dimethyl ester was also studied by voltammetry and polarography. Substituent effects and the influence of bases on the oxidative behaviour of these compounds were studied. The results are discussed in relation to the biological role of bile pigments. Phycocyanobilin dimethyl ester shows a clearly different oxidative behaviour with respect to the bile pigments tested.

Reactivity of pyrrole pigments, XIX. On the structure of Cu(II) and Zn(II) chelates of dipyrrins in solution

SummaryThe Cu(II) and Zn(II) chelates of 1,2,3,7,9-pentamethyldipyrrin and 1,2,3,7,9-pentamethyl-8-sulfodipyrrin are studied. When metal acetates are used for the formation of the metal complexes, dipyrrinate metal acetates could be detected as precursors of thebis-dipyrrinates.ZusammenfassungDie Cu(II)- und Zn(II)-Chelate von 1,2,3,7,9-Pentamethyldipyrrin und 1,2,3,7,9-Pentadimethyl-8-sulfodipyrrin wurden untersucht. Bei Einsatz von Metalldiacetaten für die Komplexbildung wurden Dipyrrinmetallacetate als Vorläufer derbis-Dipyrrinate nachgewiesen.

Reactivity of pyrrole pigments, XXI: Structure and reactivity of Cu(II) and Zn(II) bilindione chelates

SummarySeveral Mn, Cu, and Zn chelates of etiobiliverdin-IV-γ, mesobiliverdin-IXα, and its dimethyl ester are studied. The results show that the chemical constitution of the Cu biliverdin chelate corresponds to a formal metal oxidation state of (II) coordinated to a neutral radical of the NH trideprotonated biliverdin. The reactivity of the Cu(II) bilindione chelates in nucleophilic solvents agrees with that expected for a π neutral radical structure of the ligand; in CH3OH, they undergo oxidation towards dimethoxybilipurpurins. The magnetic behaviour of Cu(II) etiobiliverdinate-IV-γ in the solid state shows an intramolecular weak antiferromagnetic coupling d9Cu-to-π-radical (J=−23 cm−1) and an intermolecular weak antiferromagnetic coupling π-radical-to-π-radical (J=−45 cm−1). The analogy of this magnetic behaviour to that of the π cation radical of metalloporphyrins is discussed.ZusammenfassungEinige Mn, Cu and Zn Chelate von Etiobiliverdin-IV-γ, Mesobiliverdin-IXα und seinem Dimethylester werden untersucht. Im Komplex koordiniert ein Metallatom (mit der Formalladung II) mit einem Neutralradikal des dreifach NH-deprotonierten Bilindions. Die Reaktivität des Komplexes gegenüber nukleophilen Lösungmitteln entspricht erwartungsgemäß dem eines neutralen π-Radikals; in CH3OH wird er zu Dimethoxybilipurpurin oxidiert. Bei Cu(II)-Etiobiliverdinat-IVγ beobachtet man im festen Zustand neben schwacher, antiferromagnetischer Kupplung zwischen d9Cu und π-Radikal (J=−23 cm−1) auch eine schwache, intermolekulare, antiferromagnetische Wechselwirkung zwischen zwei π-Radikalen (J=−45 cm−1). Dieses magnetische Verhalten wird dem des π-Kationradikals von Metalloporphyrinen gegenübergestellt.