Immobilization of porphyrins in poly(hydroxymethylsiloxane)

Three tetracationic porphyrins differing in the position of charged nitrogen atoms on the peripheral substituents — 5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrin (TMPyP4), 5,10,15,20-tetrakis(N-methylpyridinium-2-yl)porphyrin (TMPyP2), 5,10,15,20-tetrakis(4-trimethylammoniophenyl) porphyrin (TMAPP), and hydrophobic 5,10,15,20-tetraphenylporphyrin (TPP), were immobilized by adsorption and encapsulation in poly(hydroxymethylsiloxane) (PHOMS). The so prepared porphyrin-PHOMS composites were characterized by porosimetry, scanning electron microscopy, fluorescence and diffuse reflectance UV-VIS spectroscopy. It was found that porphyrins are immobilized in the PHOMS matrix in the free base monomer form Their irradiation produced singlet oxygen O₂(¹Δ_g) with the lifetime of 10–30 μs.     

Influence of the macrocycle structure on the ability of Co(II)-porphyrins to oxidize in the presence of organic bases

Abstract

By spectrophotometric titration, ¹H NMR and cyclic voltammetry the processes of Co(II)-5,10,15,20-tetraphenylporphyrin, Co(II)-5,10,15,20-tetraphenyl-2,3,7,8,12,13,17,18-tetrabenzoporphyrin, Co(II)-2,3,7,8,12,13,17,18-octaphenyl-5,10,15,20-tetraazaporphyrin, Co(II)-2,3,7,8,12,13,17,18-octa(4-bromphenyl)-5,10,15,20-tetraazaporphyrin and Co(II)-2,3,7,8,12,13,17,18-octa(4-nitrophenyl)-5,10,15,20-tetraazaporphyrin interaction with imidazole (Im) in benzene in the presence and absence of atmospheric oxygen has been investigated. If the Co(II)-porphyrins with high E_pc upon complexation with the imidazole form stable mono-axial complexes Co(II)P(Im), then the Co(II)-porphyrins with low E_pc are oxidized into low-spin six-coordinate Co(III)-porphyrins with formation of bis-axial complexes Co(III)P(Im)₂. The thermodynamic and kinetic parameters of the coordination and oxidation processes have been calculated and corresponding structural correlations have been carried out.     

Porphyrinylphosphonate-Based Metal–Organic Framework: Tuning Proton Conductivity by Ligand Design

A novel metal–organic framework [Zn₃(Ni-H₂TPPP)(Ni-H₄TPPP)(Ni-H₅TPPP) ⋅ 7(CH₃)₂NH₂ ⋅ DMF ⋅ 7 H₂O] (where Ni-H_xTPPP (x=2,4,5) are partially deprotonated [5,10,15,20-tetrakis(3-(phosphonatophenyl)-porphyrinato(2-))]nickel(II) species), IPCE-2Ni , with outstanding proton conductivity (1.0×10⁻² S cm⁻¹ at 75 °C and 95 % relative humidity) has been obtained. The high concentration of free phosphonate groups and compensating dimethylammonium cations bound by hydrogen bonds in the unique crystal structure of IPCE-2Ni is a key factor responsible for the observed high proton conductivity, which is one order of magnitude higher than for the corresponding MOF based on 5,10,15,20-tetrakis(4-(phosphonatophenyl)porphyrinato(2-))]nickel(II) IPCE-1Ni and comparable with that of leaders among MOFs.     

Light Induced Redox Reactions of Water Soluble Porphyrins,sensitization of hydrogen generation from water by zincporphyrin derivatives

The photoredox behaviour of two water soluble derivatives of zincporphyrin, 5,10,15,20-tetra-p-sulfonatophenyl ( 1 ) and 5,10,15,20-tetra-p-N-methylpyridiniochloride ( 2 ), was investigated using laser and continuous photolysis techniques. Photoexcitation produces triplet states whose lifetimes in aqueous solution exceeds 1 ms. These triplet states can be quenched reductively by donors such as EDTA and oxidatively by acceptors such as methylviologen (MV²⁺). Electron transfer to MV²⁺ is greatly influenced by the charge of the porphyrin, rate constants being 1.4 x 10¹⁰M^?1S^?1 and 2 × 10⁶M^?1S^?1 for 1 and 2 , respectively. In the presence of colloidal Pt catalyst, the cationic porphyrin sensitizes photoreduction of water to hydrogen with remarkable efficiency.     

Synthesis of glycosylated porphyrins as neutral ionophores for a berberine-sensitive electrode

For preparing a berberine-sensitive electrode, 5,10,15,20-tetrakis[2-(2,3,4,6-tetraacetyl-β-D-glucopyranosyl)-1-O-phenyl]porphyrin (T(o-glu)PPH₂) was synthesized from the reaction of pyrrole with ortho-acetylglycosylated benzaldehyde by Lindsay’s method. The electrode based on T(o-glu)PPH₂ with an optimized membrane composition exhibits Nernstian response to berberine in the concentration range 2.4 × 10^–7–5.0 × 10^–3 mol L^–1, with a pH range from 3.9 to 10.2, and a fast response time of 30 s. The electrode shows fair selectivity towards berberine with respect to common co-existing species. T(o-glu)PPH₂ shows better potentiometric response characteristics comparing to chloro[5,10,15,20-tetrakis[2-(2,3,4,6-tetraacetyl-β-D-glucopyranosyl)-1-O-phenyl]-porphinato]-manganese (MnT(o-glu)PPCl) and better selectivity towards berberine than tetraphenylporphyrin (TPPH₂). The effect of the composition of the electrode membrane has been studied and the experimental conditions optimized. The contents of berberine in pharmaceutical tablets were determined by direct potentiometry and the results agreed with values obtained by the pharmacopoeia method. Received: 17 July 2000 / Revised: 18 September 2000 / Accepted: 23 October 2000     

Unusual sensitivity to the concentration of ethanol in the boron trifluoride/ethanol-catalyzed synthesis of 5,10,15,20-tetrakis-(4-cyano-2,6-dimethylphenyl)porphyrin by the lindsey method

The boron trifluoride/ethanol-catalyzed condensation of 4-cyano-2,6-dtmethylbenzaldehyde 1b with pyrrole by the Lindsey method to give the new, ortho-disubstituted 5,10,15,20-tetrakis(4-cyano-2,6-dimethylphenyl)porphyrin 2 was found to be highly sensitive to the concentration of ethanol. In the absence of ethanol the yield of porphyrin is only 1%. Yields can be increased to 20–25% with ethanol concentrations of 0.05–0.1% (v/v) but they decrease rapidly at higher concentrations of ethanol. Optimized procedures for the preparation of both 1b and 2 are described and the newly synthesized molecules are characterized by nmr (¹H and ¹³C), mass spectra and elemental analysis.     

Synthesis and Spectral Properties of Ni(II), Pd(II), Pt(II), and Pt(IV) Tetraphenyltetrabenzoporphyrinates

Complexation reactions of 5,10,15,20-tetraphenyltetrabenzoporphyrin and transmetallation of its cadmium complex with nickel(II) acetate, Ni(II), Pd(II), and Pt(II) chlorides in dimethylformamide and phenol have been studied. The corresponding Ni(II), Pd(II), and Pt(II) porphyrinates have been synthesized. Pt^IVBr₂ porphyrinate has been obtained by the treatment of Pt(II) 5,10,15,20-tetraphenyltetrabenzoporphyrinate with bromine in chloroform. The obtained compounds have been characterized by elemental analysis, electronic absorption and ¹H NMR spectroscopy and mass spectrometry.     

Formation of supramolecular complex between imidazole and dichloro(5,10,15,20-tetraphenylporphinato)zirconium(IV)

By the reaction of 5,10,15,20-tetraphenyl-21H,23H-porphin (H₂TPP) with zirconium tetrachloride in boiling benzonitrile a complex was obtained, dichloro(5,10,15,20-tetraphenylporphinato)zirconium(IV), (Cl)₂ZrTPP. The equilibrium and reaction rate of stepwise reactions of (Cl)₂ZrTPP with imidazole (Im) in toluene were investigated by spectrophotometry. It was established that the three steps of the complex formation include reversible processes of coordination of Im molecule and substitution of 2Cl⁻ by the second and third Im molecules. The products of the first and second stages of the reaction, (Cl)₂(Im)ZrTPP and [(Cl)(Im)₂ZrTPP]⁺Cl⁻, respectively, are unstable and dissociate slowly at one Zr-Cl bond. By the analysis of the numerical values of the reactions parameters with accounting for the existence of definite spectral response to the presence of an organic base was shown a better prospect of application of (Cl)₂ZrTPP in sensor systems than those of metallophtalocyianines and doubly charged cation complexes with porphyrins.     

A New Nonconjugated Naphthalene Derivative of Meso-tetra-(3-hydroxy)-phenyl-porphyrin as a Potential Sensitizer for Photodynamic Therapy

A new 5,10,15,20-tetra-(phenoxy-3-carbonyl-1-amino-naphthyl)-porphyrin was prepared by an isocyanate condensation reaction and its photophysical properties fully evaluated, both in terms of photostability and singlet oxygen production. It shows considerably enhanced photostability when compared with the parent 5,10,15,20-tetra-(3-hydroxy-phenyl)-porphyrin, with the photodegradation quantum yields for T(NAF)PP and T(OH)PP being 4.65 × 10⁻⁴ and 5.19 × 10⁻³, respectively. Its photodynamic effect in human carcinoma HT-29 cells was evaluated. The new porphyrin showed good properties as a sensitizer in photodynamic therapy with an in vitro cytotoxicity IC₅₀ value of 6.80 μg mL⁻¹ for a 24 h incubation. In addition to the potential of this compound, the synthetic route used provides possibilities of extension to a wide range of new sensitizers.     

Alternating copolymerization of cyclohexene oxide and carbon dioxide under cobalt porphyrin catalyst

Cobalt porphyrin complexes（TPPCo^ⅢX）（TPP = 5,10,15,20-tetraphenyl-porphyrin;X = halide） in combination with bis（triphenylphosphine） iminium chloride（PPNCl） were used for the copolymerization of cyclohexene oxide and CO₂. The highest turnover frequency of 67.2 h^-1 was achieved after 13 h at 20℃,and the obtained poly（1,2-cyclohexylene carbonate）（PCHC） showed number average molecular weight（M_n） of 10×10³.Though the obtained PCHC showed atactic structure,the m-centered tetrads content reached 58.1%at CO₂ pressure of 1.0 MPa,and decreased to 51.9%at CO₂ pressure of 6.0 MPa,indicating that it was inclined to form atactic polymer at high CO₂ pressure.     

Fluorescent Arylphosphonic Acids: Synergic Interactions between Bone and the Fluorescent Core

Herein, we report the third generation of fluorescent probes (arylphosphonic acids) to target calcifications, particularly hydroxyapatite (HAP). In this study, we use highly conjugated porphyrin-based arylphosphonic acids and their diesters, namely 5,10,15,20-tetrakis[m-(diethoxyphosphoryl)phenyl]porphyrin ( m -H₈TPPA-OEt₈ ) and 5,10,15,20-tetrakis [m-phenylphosphonic acid]porphyrin ( m -H₈TPPA ), in comparison with their positional isomers 5,10,15,20-tetrakis[p-(diisopropoxyphosphoryl)phenyl]porphyrin ( p -H₈TPPA-iPr₈ ) and 5,10,15,20-tetrakis [p-phenylphosphonic acid]porphyrin ( p -H₈TPPA ), which have phosphonic acid units bonded to sp² carbon atoms of the fluorescent core. The conjugation of the fluorescent core is thus extended to the (HAP) through sp²-bonded −PO₃H₂ units, which generates increased fluorescence upon HAP binding. The resulting fluorescent probes are highly sensitive towards the HAP in rat bone sections. The designed probes are readily taken up by cells. Due to the lower reported toxicity of ( p -H₈TPPA ), these probes could find applications in monitoring bone resorption or adsorption, or imaging vascular or soft tissue calcifications for breast cancer diagnosis etc.     

Effect of the nature of the tetrapyrrole macrocycle on the transmetallation of Zn2+ and Cd2+ porphyrins with PdCl2 in dimethylformamide

Transmetallation of zinc (Zn²⁺) and cadmium (Cd²⁺) complexes of 5,10,15,20-tetraphenylporphin, 5,10,15,20-tetra(4-chlorophenyl)porphyrin, 5,10,15,20-tetra(4-methoxyphenyl)porphyrin, tetrabenzoporphyrin, and octaphenyltetraazaporphyrin with PdCl₂ in DMF was studied by spectrophotometry. The influence of the nature of the tetrapyrrole macrocycle on the reactivity of Zn²⁺ porphyrins toward palladium chloride in boiling DMF was established. Palladium(II) complexes of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra(4-chlorophenyl)porphyrin, 5,10,15,20-tetra(4-methoxyphenylporphyrin), and tetrabenzoporphyrin were prepared and identified.     

Synthesis,Spectral, and Coordination Properties of Halogen-Substituted Tetraarylporphyrins

2,3,7,8,12,13,17,18-Ocatbromo-5,10,15,20-tetra-(4-chloroprienyl)porphyrin and 2,3,7,8,12,13,17,18-octachloro-5,10,15,20-tetra-(4-bromophenyl)porphyrin have been synthesized. The obtained compounds have been identified by electronic absorption and ¹H NMR spectroscopy as well as mass spectrometry. The complex-forming properties of the synthesized porphyrins in the zinc acetate (II)-acetonitrile system at 278–298 K have been studied. Kinetic parameters of the formation of the corresponding zinc complexes in acetonitrile have been determined.

     

Direct introduction of heterocyclic units into porphyrin derivatives

In the reaction with quinazoline and 5-phenyl-1,2,4-triazin-5(2H)-one, 5,10,15,20-tetra(4-methoxyphenyl)porphyrin exhibits nucleophilic properties. In quinazoline excess, C—C coupling occurs at the C=N bond of azines and position 3 of the aryl ring to form 5,10,15,20-tetrakis(3-heteryl-4-methoxyphenyl)porphyrins. Monoheteryl-substituted porphyrin was obtained by the reaction of equimolar amounts of 5,10,15,20-tetra(4-methoxyphenyl)porphyrin and 5-phenyl-1,2,4-triazin-5(2H)-one.     

Synthesis and properties of ms- and β-substituted Pt(II) and Pt(IV) tetraphenylporphyrinates

The interaction of 5,10,15,20-tetraphenylporphyrin, 5,10,15,20-tetra-(4-chlorophenyl)porphyrin, 2-bromo-5,10,15,20-tetraphenylporphyrin, and 2,3,12,13-tetrabromo-5,10,15,20-tetraphenylporphyrin with platinum(II) chloride in boiling phenol has been studied. The corresponding platinum(II) porphyrinates have been synthesized; their subsequent treatment with bromine in chloroform resulted in platinum(IV) porphyrinates. The Pt(II) and Pt(IV)(Br)₂ porphyrinates have been identified by elemental analysis, electron absorption, IR, and ¹H NMR spectroscopy.     

A one‐dimensional manganese(III)–porphyrin coordination polymer: crystal structure and photophysical properties

A novel manganese(III)–porphyrin complex, namely, catena‐poly[[chloridomanganese(III)]‐μ₂‐5,10,15,20‐tetrakis(pyridin‐3‐yl)‐21H,23H‐porphinato(2?)‐κ⁵N²¹,N²²,N²³,N²⁴:N⁵], [MnCl(C₄₀H₂₄N₈)]_n, 1 , was prepared by the hydrothermal reaction of manganese chloride with 5,10,15,20‐tetrakis(pyridin‐3‐yl)‐21H,23H‐porphine. The crystal structure was determined by single‐crystal X‐ray diffraction. The porphyrin macrocycle exhibits a saddle‐like distortion geometry. The Mn^III atom has a six‐coordination geometry. Each porphyrin unit links to two neighbouring units to yield a one‐dimensional coordination polymer. These chains are further interlinked by hydrogen bonds to form a two‐dimensional network. The complex shows red photoluminescence emission bands in ethanol solution, which can be attributed to ligand‐to‐ligand charge transfer (LLCT) accompanied by partial metal‐to‐ligand charge transfer (MLCT), as revealed by TDDFT calculations.     

Regulation of α‐Chymotrypsin Catalysis by Ferric Porphyrins and Cyclodextrins

Positively charged α‐chymotrypsin (ChT) formed a 1:1 complex with negatively charged 5,10,15,20‐tetrakis(4‐sulfonatophenyl)porphyrinato iron(III) (FeTPPS) in phosphate buffer at pH 7.4 through electrostatic interaction. In spite of the large binding constant (K=4.8×10⁵ M ^?1), FeTPPS could not completely inhibit the catalysis of ChT in the hydrolysis of the model substrate, N‐succinyl‐L ‐phenylalanine p‐nitroanilide (SPNA). The degree of inhibition (60 %) was saturated at 1.6 equivalents of FeTPPS, which indicates that covering of the active site of ChT by FeTPPS was insufficient. The enzymatic activity lowered by FeTPPS was entirely recovered for the freshly prepared sample when the porphyrin on the protein surface was detached by per‐O‐methylated β‐cyclodextrin (TMe‐β‐CD), which formed a stable 1:2 inclusion complex with FeTPPS (K₁=1.26×10⁶ M ^?1, K₂=6.3×10⁴ M ^?1). FeTPPS gradually induced irreversible denaturation of ChT, and the denatured ChT further lost its catalytic ability. No repairing effect of TMe‐β‐CD was observed with irreversibly denatured ChT. A new reversible inhibitor, 5,10,15,20‐tetrakis[4‐(3,5‐dicarboxyphenylmethoxy)phenyl]porphyrinato iron(III) (FeP8M), was then designed, and its inhibitory behavior was examined. FeP8M formed very stable 1:1 and 1:2 FeP8M/ChT complexes with ChT, the K₁ and K₂ values being 2.0×10⁸ and 1.0×10⁶ M ^?1, respectively. FeP8M effectively inhibited the ChT‐catalyzed hydrolysis of SPNA (maximum degree of inhibition=85 %), and the activity of ChT was recovered by per‐O‐methylated γ‐cyclodextrin. No irreversible denaturation of ChT occurred upon binding with FeP8M. The kinetic data support the observation that, for nonincubated samples, both inhibitors did not cause significant conformational change in ChT and inhibited the ChT activity by covering the active site of the enzyme.     

The first lanthanide(III) monoporphyrin complex liquid crystal

Hydroxy [5,10,15,20-tetra[P-decyloxy- ^m -methyloxy)phenyl]porphyrin Yb(III) exhibits a discotic hexagonal columnar phase, it is the first example of a monoporphyrin rare earth complex liquid crystal.     

Influence of chloroform on crystalline products yielded in reactions of 5,10,15,20‐tetraphenylporphyrin with HCl and copper(II) salts

Chloroform was found to occupy the lattice of the protonated porphyrin and to promote crystallization of a different polymorphic form of a metalloporphyrin. The structure of 5,10,15,20‐tetraphenylporphyrin‐21,23‐diium dichloride chloroform octasolvate, C₄₄H₃₂N₄²⁺·2Cl⁻·8CHCl₃, (I), in the solid state is described and compared with related solvates. The porphyrin macrocycle displays a distorted saddle shape, with chloride anions above and below the ring. Seven chloroform molecules are bound via C—H...Cl hydrogen bonds, while the link with the eighth solvent molecule is weaker. A new monoclinic polymorph of (5,10,15,20‐tetraphenylporphyrinato)copper(II), [Cu(C₄₄H₂₈N₄)], (II), crystallized from chloroform, is also presented.     

A kinetic method for the determination of zinc(II) in presence of a large excess of cadmium(II) by the different dissociation rate of their complexes with 5,10,15,20-tetrakis(4-sulfonatophenyl)porphine

Summary Acid-dissociation reaction of the cadmium(II) complex of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphme (H₂tspp) proceeds about 10¹² times as fast as that of the zinc(II) complex. This provides the basis for a kinetic determination of zinc(II) in presence of a large excess of cadmium (II). The absorbance at soret-band (421 nm) of Zn(II)(tspp) was used to monitor the reaction. At 5.0×10^–2 M hydrogen ion concentration, Cd(II)(tspp) dissociates completely to Cd²⁺ in 1 s and only the reaction associated with Zn(II)(tspp) is observed during the reaction time from 30 s to 5 min. Zinc(II) concentration <10^–6 M is determined in the presence of 10^–2 M cadmium(II). The molar absorption coefficient is 2.7×10⁵ M ^–1 cm^–1. Iron(III), aluminum(III) and cobalt(II) being masked sodium tartrate, this method is highly selective and is free from interferences of most substances usually encountered. The method was applied to determine zinc(II) in tap water and in cadmium(II) sulfate.