Porphyrin Residues Research Articles

Density functional theory investigation of the coordination of Zn(II)-tetraphenylporphyrin with 1,2,3-triazole ligands

In this paper, we report density functional theory (DFT) studies to fully understand the coordination interactions between 1,4-disubstituted 1,2,3-triazole derivatives and the metal center of Zn(II)-porphyrins. Coordination through the most electron-rich N3 atom of the triazole heterocycle is more favorable. However, the energy difference between the N2- and N3-coordinated isomers is moderate and the less stable is likely also present in the solution. The binding of 1,4-disubstituted 1,2,3-triazole ligands to oxidized and reduced Zn(II)-porphyrins has been also investigated. Upon reduction, the binding interactions are extremely weak and the formation of the complex is not favorable anymore. In contrast, the binding energy is considerably increased upon oxidation of the Zn(II)-porphyrin moiety thus leading to more stable complexes. The calculations fully support experimental findings and explain the differences observed for the redox potentials of complexed and uncomplexed Zn(II)-porphyrin residues.

Porphyrin Network Polymers Prepared via a Click Reaction and Facilitated Oxygen Permeation Through Their Membranes

Network polymers of cobaltporphyrin derivatives are prepared by a facile click reaction via the Michael addition of acetoacetate-substituted tetraphenyl cobaltporphyrin and tri- or tetra-acrylates. The conversion is saturated for 1 h in the presence of a catalyst, which almost reaches the same gelation point of the formed network polymers. Deeply and homogeneously red-colored membranes with a sub-micrometer thickness are yielded on a porous supporting membrane. They are still tough even with a very high content of the rigid porphyrin residue. The oxygen permeability is high, at 10-100 Barrer, and the oxygen/nitrogen permselectivity (PO2/PN2) is significantly enhanced with the porphyrin content reaching 30, for the membranes with ca. 70 wt% porphyrin content.

Synthesis of oligo-DNA containing hydrophilic porphyrin in the main chain, and its energy transfer behaviour in duplex state

DNA is one of the best candidates as building blocks for bottom-up approach to nanometre size architecture in nanotechnology. In natural photosynthetic system, the arrangement of porphyrin derivatives with regulated distances, orders and orientations provides an efficient photon-energy collecting and transmission. We have studied about chromophore arrangement on DNA assembly as a simple artificial model of photosynthetic and photo-energy transmission systems. In order to prepare DNAs containing porphyrin residues at desired sites, a hydrophilic porphyrin amidite derivative, which can be utilised on automatic DNA synthesizer, was synthesised. The porphyrin amidite derivative was applied for automatic DNA synthesizer to give single-strand DNA (ssDNA) containing porphyrin set in the chain. The obtained ssDNA was mixed with complementary counter strand having another chromophore black hole quencher-3 (BHQ-3) to form duplex by self-assembly. The quenching behaviour by energy transfer from the porphyrin to BHQ-3 was monitored by fluorescence measurement.

Moleculary imprinted polymers with metalloporphyrin-based molecular recognition sites coassembled with methacrylic acid.

A diastereoselective molecularly imprinted polymer (MIP) for (-)-cinchonidine, PPM(CD), was prepared by the combined use of methacrylic acid and vinyl-substituted zinc(II) porphyrin as functional monomers. Compared to MIPs using only methacrylic acid or zinc porphyrin as a functional monomer, PM(CD) and PP(CD), respectively, PPM(CD) showed higher binding ability for (-)-cinchonidine in chromatographic tests using the MIP-packed columns. Scatchard analysis gave a higher association constant of PPM(CD) for (-)-cinchonidine (1.14 x 10(7) M(-1)) than those of PP(CD) (1.45 x 10(6) M(-1)) and PM(CD) (6.78 x 10(6) M(-1)). The affinity distribution of binding sites estimated by affinity spectrum analysis showed a higher percentage of high-affinity sites and a lower percentage of low-affinity sites in PPM(CD). The MIPs containing a zinc(II) porphyrin in the binding sites, PPM(CD) and PP(CD), showed fluorescence quenching according to the binding of (-)-cinchonidine, and the quenching was significant in the low-concentration range, suggesting that the high-affinity binding sites contain the porphyrin residue. The correlation of the relative fluorescence intensity against log of (-)-cinchonidine concentrations showed a linear relationship. These results revealed that the MIP having highly specific binding sites was assembled by the two functional monomers, vinyl-substituted zinc(II) porphyrin and methacrylic acid, and they cooperatively worked to yield the specific binding. In addition, the zinc(II) porphyrin-based MIPs appeared to act as fluorescence sensor selectively responded by binding events of the template molecule.

Stacked Porphyrin Arrays from Hydrogen-Bonded Porphyrin–Resorcinol 1D Chains

Abstract The Ni(II) complex of monoresorcinol derivative of a sterically unhindered tetraalkylporphyrin (3) affords adducts 3•(methanol) and 3•1.5(acetophenone). In the crystals, porphyrin 3 forms hydrogen-bonded (O–H···O–H) polyresorcinol chains with the porphyrin residues sticking out of the chains. The chains are self-assembled in such a manner as to give closely stacked interchain porphyrin columns, while the guest molecules are either firmly bound to the hydrogen-bonding sites (in the case of methanol) or incorporated in the channels running in parallel with the porphyrin stacks (in the case of acetophenone). The formation of such a stacked porphyrin array is not observed when the guest is changed to 4-heptanone or when the porphyrin is changed to a sterically hindered one 4 or 5 with full substitution at the meso- or the β-positions. The mode of interchain porphyrin stacking is discussed in light of the crystal structures of adducts 3•(4-heptanone), 4•pyridine, and 5•(2-nonanone).

Electrochemical synthesis and characterisation of polythiophene conducting polymers functionalised by metal-containing porphyrin residue

Two different copolymers of 2,2′-bithiophene and of new thiophene derivatives, bearing in the β position a porphyrin macrocycle, either free or complexed with Ni(II), have been electrogenerated and studied. The electrochemical behaviour of the relevant coatings has been compared, and the complexing ability of the macrocycle with respect to Ni(II) ion has been investigated. Moreover, the possibility of growing the metal-containing polymer on a micro Pt disk has been checked. The resulting modified microelectrode has been characterised and tested.

A μ-Oxo-bis[iron(III) porphyrin] Complex

Partial nitration of iron(III) 2,3,7,8,12,13,17,18-octaethylporphyrin chloride [Fe III (OEP)Cl] gives the μ-oxo-bis(5,15-dinitro) compound μ-oxo-bis[2,3,7,8,12,-13,17,18-octaethyl-5,15-dinitroporphyrinato)iron(III)], [Fe 2 (C 36 H 42 N 6 O 4 ) 2 O], which is similar to other μ-oxo-iron(III) porphyrin complexes but with less ruffling of the porphyrin structure. The porphyrin planes are not parallel [the angle between plane normals is 169 (2)°] and the Fe-O-Fe angle is 167.9(3)°. As expected, the Fe atoms are significantly displaced from the porphyrin planes towards the bridging O atom : 0.46 A for Fe1 and 0.49 A for Fe2. The two porphyrin residues are eclipsed with respect to their C atoms, but the nitro groups are staggered by 90° from one residue to the other.

Action of chlorophyllase purified from rye seedlings on light-harvesting bacteriochlorophyll of chromatophores and spheroplasts from Rhodospirillum rubrum.

1. The chlorophyllase [EC 3.1.1.14] purified from greened rye seedlings hydrolyzed the bacteriochlorophyll isolated from Rhodospirillum rubrum, but not the pigment bound to the membrane of chromatophores or spheroplasts from the bacterium. 2. Acetone, if added at such concentrations that the bound bacteriochlorophyll would not be solubilized, enabled the enzyme to hydrolyze the bound pigment. The acetone concentrations required for half the maximum hydrolysis rates were 16% with chromatophores and 7% with spheroplasts. 3. The enzymic hydrolysis of the bound bacteriochlorophyll in the presence of acetone removed bacteriochlorophyllide from the membrane, leaving its esterifying alcohol, possibly all-trans-geranylgeraniol, in situ. 4. Washing of chromatophores with 30% acetone removed about 10% of the bound bacteriochlorophyll. The bound pigment remaining after washing was not hydrolyzed by the enzyme unless acetone was added. 5. It seems possible that light-harvesting bacteriochlorophyll was mostly, if not all, bound to the inner surface of chromatophores (the outer surface of spheroplasts), having its esterifying alcohol residue buried in the membrane and its porphyrin residue emerging from the membrane into the inside solution; thus, chlorophyllase could not make contact with the ester linkage between the esterifying alcohol and porphyrin moieties of the pigment unless the esterifying alcohol residue was partly exposed.

The Mössbauer recoil-free fraction and structure. Part 1. α, β, γ, δ-tetraphenylporphinatodihydroxytin(IV)-bis(chloroform)-bis(carbon tetrachloride) solvate

The structure of α, β, γ, δ-tetraphenylporphinatodihydroxytin(IV) (TPPSn(OH) 2) has been determined as its bis(chloroform)-bis(carbon tetrachloride) solvate by Patterson and Fourier techniques to a final ‘R’-factor of 15.14% for 4380 independent reflections. Purple crystals of the material are triclinic, space group P1, with a = 12.229(6), b = 12.310(9), c = 9.592(8) Å, α = 102.58(1), β = 109.64(5), γ = 91.78(8)°, and are composed of stacks of non-interacting TPPSn(OH) 2 molecules, with the solvate molecules occupying spaces in the lattice. The geometry at the tin is only slightly distorted from regular octahedral, with SnN bonds of normal length (2.09(5) Å), but with very short bonds to oxygen (2.00(3) and 2.03(5) Å). Tin-119 Mössbauer resonance area data have been collected in the temperature range 77 ⩽ T ⩽ 153 K, and a semi-logarithmic plot of resonance area versus temperature is linear in this temperature range, yielding values of the logarithmic temperature coefficient of the recoil-free fraction, a, and of the characteristic Mössbauer temperature, θ M, of −0.01193 K −1 and 122.3 K, respectively. The data have also been used to evaluate the isotropic mean-square amplitudes of vibration, <x iso(T) 2>, of the tin atom, normalised to the value at 298 K available from the crystallographic study, in the same temperature range. Root-mean-square values of the vibrational amplitude range from 0.125 Å at 77 K to 0.148 Å at 153 K. From the Goldanskii-Karyagin effect data, it was concluded that the sign of the electric field gradient, V zz, assumed to be coincident with the pseudo-four-fold axis of the molecule, is negative, and that the tin atom vibrates with greater amplitude in the plane of the porphyrin residue (perpendicular to V zz). The temperature coefficient of the root-mean-square amplitude of vibration is significantly larger in the out-of-plane direction (along the OSnO axis) (4.184 × 10 −4 Å K −1 than in the in-plane direction (2.618 × 10 −4 Å K −1), reflecting the constraining nature of the porphyrin residue. Absolute values of the recoil-free fraction, f a were estimated to be 0.100 at 77 K reducing to 0.0404 at 153 K.