Photocatalytic CO2 Reductions Catalyzed by meso-(1,10-Phenanthrolin-2-yl)-Porphyrins Having a Rhenium(I) Tricarbonyl Complex

We have prepared Zn and free-base porphyrins appended with a fac-Re(phen)(CO)₃Br (where phen is 1,10-phenanthroline) at the meso position of the porphyrin, and performed photocatalytic CO₂ reduction using porphyrin–Re dyads in the presence of either triethylamine (TEA) or 1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzo[d]imidazole (BIH) as an electron donor. The Zn porphyrin dyad showed a high turnover number for CO production compared with the free-base porphyrin dyad, suggesting that the central Zn ion of porphyrin plays an important role in suppressing electron accumulation on the porphyrin part and achieving high durability of the photocatalytic CO₂ reduction using both TEA and BIH. The effect of acids on the CO₂ reduction was investigated using the Zn porphyrin–Re dyad and BIH. Acetic acid, a relatively strong Brønsted acid, rapidly causes the porphyrin's color to fade upon irradiation and dramatically decreases CO production, whereas proper weak Brønsted acids such as 2,2,2-trifluoroethanol and phenol enhance the CO₂ reduction.     

Intermolecular complexes of singly linked bisporphyrins with trinitrobenzene

Several covalently linked bisporphyrin systems, free-base (H₂P---H₂P), hybrid bisporphyrins (Zn---H₂P) and Zn(II) dimers (ZnP---ZnP) and their 1:1 molecular complexes with sym 1,3,5-trinitrobenzene have been investigated by optical absorption and emission, and magnetic resonance spectroscopic methods. In these systems, two porphyrin units are linked singly through one of the meso aryl groups via ether linkages of variable length. The bisporphyrins cooperatively bind a molecule of a π-acceptor; 1,3,5-trinitrobenzene (TNB). The binding constant values vary with interchromophore separation. Maximum binding is observed in the bisporphyrin bearing a two-ether covalent linkage. It is found that TNB quenches the fluorescence of the two porphyrine units in a selective manner. It is suggested that a critical distance between the two porphyrin units is necessary for the observance of maximum cooperative intermolecular binding with an acceptor.     

The first phosphite complex of a metalloporphyrin

(Di­phenyl phosphite‐κO)(5,10,15,20‐tetra­phenyl­porphyrinato‐κ⁴N)­manganese(III) hexa­fluoro­antimonate(V), [Mn(C₄₄H₂₈N₄)(C₁₂H₁₁O₃P)](SbF₆), is the first example of a structurally characterized di­aryl or di­alkyl phosphite complex of a metal–porphyrin ion. The axial phosphite ligand binds to the Mn^III ion via the P=O O atom, affording a nominally five‐coordinate complex with an Mn—O distance of 2.120 (4) Å. The mean porphyrin Mn—N distance is 2.000 (4) Å and the Mn^III ion is displaced from the 24‐atom porphyrin mean plane by 0.1548 (13) Å towards the axial O atom. The porphyrin adopts a marked saddle conformation, with a small domed component. The saddle distortion of the porphyrin ligand reflects the tight back‐to‐back dimers formed in the lattice by pairs of neighboring cations. The `non‐covalent' dimers in the lattice exhibit an unusual (weak) η²‐type coordination of a pyrrole C=C bond from a neighboring mol­ecule, with Mn^III⃛C distances of 3.697 (5) and 3.537 (5) Å.     

Über Synthesen der Verbindungen von Mn,Fe, Co,Ni, Cu und Zn mit Hydrazidokohlensäure

Zusammenfassung Die Synthesen und einige Eigenschaften der Verbindungen von zweiwertigem Mn, Cu, Fe, Co, Ni und Zn mit Hydrazidokohlensäure werden beschrieben. Die Verbindungen von Fe, Co, Ni und Zn sind Hydrazinium-hydrazidocarbonato-metallate(II) der allgemeinen Formel N₂H₅[Me ^II(N₂H₃COO)₃]·H₂O, die von Mn und Cu sind aber einfache Hydrazido-carbonate der FormelMe ^II(N₂H₃COO)₂·n H₂O. Die Ergebnisse magnetochemischer Messungen sowie der orientierender Messungen der thermischen Eigenschaften werden angegeben.

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The syntheses and some properties of the compounds of bivalent Mn, Fe, Co, Ni, Cu and Zn with hydrazido-carbonic acid are described. The compounds of Fe, Co, Ni and Zn are hydrazinium hydrazido-carbonato-metallates(II) with the formula N₂H₅[Me ^II(N₂H₃COO)₃]·H₂O. The compounds of Mn and Cu are hydrazido-carbonatesMe ^II(N₂H₃COO)₂·n H₂O. The results of magnetic and preliminary measurements of thermal properties are given.

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J. Slivnik, A. malc, B. Sedej undM. Vilhar, Vestnik SKD (Bull. Soc. chim. Slovène)11, 53 (1964).     

Synthesis of oligo(p-phenylene)-linked dyads containing free base, zinc(II) or thallium(III) porphyrins for studies in artificial photosynthesis

A series of (p-phenylene)_n-linked meso-mesityl-substituted porphyrin dyads (n=2-4) was prepared via Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base porphyrin dyads were demetalated. The series of free base porphyrin dimers (n=1-4), four other porphyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl meso substituents), and several benchmark monomers were converted to the thallium(III)chloride complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and benchmark monomers have been prepared.     

TRANSFER OF EXCITATION ENERGY BETWEEN PORPHYRIN CENTERS OF A COVALENTLY-LINKED DIMER*

Abstract— Three covalently-linked porphyrin hybrid dimers were synthesized, each containing a metallotetraarylporphyrin [Zn(II), Cu(II), or Ni(II)], and a free base tetraarylporphyrin. Transfer of singlet excitation energy from the metalloporphyrin center to the free base porphyrin center was determined by measuring fluorescence properties. The Zn hybrid dimer displayed excellent intramolecular transfer of energy ( 85%) from the excited singlet state of the Zn(II) chromophore to the free base chromophore. No evidence for such transfer of the excited singlet state energy was found in the Ni(II) or Cu(II) analogues. From our experimental data, the fluorescence quantum yield of the Zn hybrid dimer was the same as for the free base monomer porphyrin (0.11; Seybold and Gouterman, 1969). Thus, the covalent attachment of another fluorescent porphyrin center effectively doubled the antenna size without decreasing the quantum yield even though the fluorescence quantum yield of the Zn(II) containing monomer was substantially less (0.03, according to Seybold and Gouterman, 1969) than that of the free base porphyrin. The donor-acceptor distance and the rate constant for energy transfer were calculated using the Forster equation. Assuming random orientation, a donor-acceptor distance of 15 Å was calculated with an associated rate constant (k_ci) for energy transfer of 1.9 ± 10₉ s_–1.     

meso–meso‐Linked Diarylamine‐Fused Porphyrin Dimers

A meso–meso‐linked diphenylamine‐fused porphyrin dimer and its methoxy‐substituted analogue were synthesized from a meso–meso‐linked porphyrin dimer by a reaction sequence involving Ir‐catalyzed β‐selective borylation, iodination, meso‐chlorination, and S_NAr reactions with diarylamines followed by electron‐transfer‐mediated intramolecular double C?H/C?I coupling. While these dimers commonly display characteristic split Soret bands and small oxidation potentials, they produced different products upon oxidation with tris(4‐bromophenyl)aminium hexachloroantimonate. Namely, the diphenylamine‐fused porphyrin dimer was converted into a dicationic closed‐shell quinonoidal dimer, while the methoxy‐substituted dimer gave a meso–meso, β‐β doubly linked porphyrin dimer.     

Conformation of the ground-state dimer in poly(ethylene terephthalate)

Absorbance, excitation, and emission measurements have been performed with methyl benzoate and five model compounds, C₆H₅COO (CH₂)_xOOCC₆H₅, x = 2–6. Under appropriate conditions, three of the model compounds (those with x = 3, 4, 5) show evidence for the formation of intramolecular ground-state dimers. The model compound with x = 5 can form two types of dimers which emit with different energies. The model compound with x = 3 forms one of these dimers, and the model compound with x = 4 prefers the other ground-state dimer. Molecular modeling of the dimers suggests that the two conformations of the ground-state dimers differ in the orientation of the two C?O bonds. In the one dimer these two bonds are nearly parallel, but in the other they make an angle of about 120°. © 1993 John Wiley & Sons, Inc.     

Synthesis, characterization and some properties of amide-linked porphyrin-ruthenium(II) tris(bipyridine) complexes

A new molecular dyad, comprised of a zinc-porphyrin and a ruthenium(II) tris(bipyridine) complex linked through an amide bond has been synthesized and characterized by ¹H, ¹³C NMR, UV-vis, mass-spectrometry and elemental analysis. The electrochemistry as well as the steady-state emission properties were investigated. The redox behavior of the dyad exhibits a favorable reversible characteristic. Substantial quenching of porphyrin emission was found when the Q band of 5 and 5-Zn was selectively photoexcited. This observation suggests a quenching mechanism with possible intramolecular electron transfer or energy transfer between the Ru(bpy)₃ moiety and the porphyrin free-base or Zn porphyrin moieties.     

Synthesis,infrared spectra and thermoanalytical properties of transition metal sulfite hydrazine hydrates

Transition metal sulfite hydrazine hydrates, MSO₃·xN₂H₄·yH₂O whereM=Mn, Fe, Co, Ni and Zn have been prepared and characterized by chemical analysis, infrared spectra, thermoanalytical and combustion studies. The colours,x andy parameters of the complexes varied depending upon the preparation conditions. Thermal decomposition characteristics differ from metal to metal yielding metal oxides at relatively low temperatures.

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Zusammenfassung Mittels chemischer Analyse, IR-Spektren, thermoanalytischen und Verbrennungsstudien wurden die Hydrazinhydrate der hergestellten Übergangsmetallsulfite MSO₃·xN₂H₄·yH₂O mitM=Mn, Fe, Co, Ni und Zn beschrieben. Farbe sowie die Parameterx undy der Komplexe hängen von den Herstellungsbedingungen ab. Die thermische Zersetzung, bei der bei relativ niedrigen Temperaturen Metalloxide entstehen, ist von Metall zu Metall verschieden.

     

Phenylene‐bridged Porphyrin meso‐Oxy Radical Dimers

Stable meta‐ and para‐phenylene bridged porphyrin meso‐oxy radical dimers and their Ni^II and Zn^II complexes were synthesized. All the dimers exhibited optical and electrochemical properties similar to the corresponding porphyrin meso‐oxy radical monomers, indicating small electronic interaction between the two spins. Intramolecular spin‐spin interaction through the π‐spacer was determined to be J/k_B=?15.9 K for m‐phenylene bridged Zn^II porphyrin dimer. The observed weak antiferromagnetic interaction has been attributed to less effective conjugation between the porphyrin radical and linking π‐spacer due to large dihedral angle. In the case of Zn^II complexes, both para‐ and meta‐phenylene bridged dimers formed 1D‐chain in solutions and in the solid states through Zn‐O coordination.     

Synthesis,characterisation and X-ray structure of a novel porphyrin array employing Zn–O and O–H…O bonding motifs

The preparation and characterisation of the free-base and zinc metallated derivatives of 5,10,15,20-tetrakis(4-(2-(2-hydroxyethoxy)ethoxy)phenyl)porphyrin 1 is described. The X-ray crystal structure of the Zn(II) adduct 2 dimerises in the solid state via an intermolecular polyether oxygen–Zn(II) interaction (O…Zn = 2.124(4) Å). The porphyrin dimers form discrete layers defined by a distance of 5.10 Å between the porphyrin planes in adjacent layers. A bilayer sheeting arrangement of the porphyrin macrocyclic units is achieved through cooperative hydrogen bonding of the ethoxyethanol arms to form 11-membered macrocycles containing four hydrogen bonds.     

π-Electronic Charge-Transfer Interactions in Inclusion Complexes of Fullerenens with Cyclic Dimers of Metalloporphyrins

Spectroscopic and voltammetric analyses on inclusion complexes of a fullerene such as C₆₀ with a cyclic dimer of a free-base porphyrin (1-M; M = 2H) and its metal complexes (M = Co, Ag, and Zn) showed that a charge-transfer interaction is partly responsible for the complexation.     

Programmable conformational regulation of porphyrin dimers on geometric scaffold of duplex DNA

DNA-porphyrin conjugates were designed and synthesized in which free-base and Zn-coordinated porphyrins were introduced to the N⁶-position of the internal adenosine. Conformations of the porphyrin dimer in the major groove of duplex DNA were controlled by changing the orientation and the distance between the two porphyrin moieties. The porphyrin dimers formed a thermally favorable face-to-face conformation on the duplex DNA. In the disadvantageous geometry for porphyrin dimer formation on the duplex, the porphyrins induced the DNA duplex structures to the Z-form conformation. These results indicate that the interaction of the two porphyrins and the conformation of duplex DNA are controlled by the program of DNA sequences.     

Homo‐ and Heteronuclear meso,meso‐(E)‐Ethene‐1,2‐diyl‐Linked Diporphyrins: Preparation,X‐ray Crystal Structure,Electronic Absorption and Emission Spectra and Density Functional Theory Calculations

Homo‐ and heteronuclear meso,meso‐(E)‐ethene‐1,2‐diyl‐linked diporphyrins have been prepared by the Suzuki coupling of porphyrinylboronates and iodovinylporphyrins. Combinations comprising 5,10,15‐triphenylporphyrin (TriPP) on both ends of the ethene‐1,2‐diyl bridge M₂10 (M₂=H₂/Ni, Ni₂, Ni/Zn, H₄, H₂Zn, Zn₂) and 5,15‐bis(3,5‐di‐tert‐butylphenyl)porphyrinato‐nickel(II) on one end and H₂, Ni, and ZnTriPP on the other ( M₂11 ), enable the first studies of this class of compounds possessing intrinsic polarity. The compounds were characterized by electronic absorption and steady state emission spectra, ¹H NMR spectra, and for the Ni₂ bis(TriPP) complex Ni₂10 , single crystal X‐ray structure determination. The crystal structure shows ruffled distortions of the porphyrin rings, typical of Ni^II porphyrins, and the (E)‐C₂H₂ bridge makes a dihedral angle of 50° with the mean planes of the macrocycles. The result is a stepped parallel arrangement of the porphyrin rings. The dihedral angles in the solid state reflect the interplay of steric and electronic effects of the bridge on interporphyrin communication. The emission spectra in particular, suggest energy transfer across the bridge is fast in conformations in which the bridge is nearly coplanar with the rings. Comparisons of the fluorescence behaviour of H₄10 and H₂Ni10 show strong quenching of the free base fluorescence when the complex is excited at the lower energy component of the Soret band, a feature associated in the literature with more planar conformations. TDDFT calculations on the gas‐phase optimized geometry of Ni₂10 reproduce the features of the experimental electronic absorption spectrum within 0.1 eV.     

Towards tuning PDT relevant photosensitizer properties: comparative study for the free and Zn2+ coordinated meso-tetrakis[2,6-difluoro-5-(N-methylsulfamylo)phenyl]porphyrin

The spectroscopic, photochemical, and biological studies of 5,10,15,20-tetrakis[2,6-difluoro-5(N-methylsulfamylo)phenyl]porphyrinate Zn(II) (ZnF₂PMet) were carried out including absorption and fluorescence spectra, fluorescence quantum yields, triplet absorption spectra, triplet lifetimes, singlet oxygen quantum yield, and reactive oxygen species (ROS) detection under biological conditions and compared with its free-base analog (F₂PMet). Zinc coordination into the porphyrin ring results in decrease of hydrophobicity and in higher cellular uptake. F₂PMet localized specifically in endoplasmic reticulum and mitochondria while the ZnF₂PMet is more diffused all over the cell, bonded to membrane proteins, as assessed by fluorescence microscopy. Zn-porphyrin exhibits greater singlet oxygen quantum yield than its free-base analog. Studies with fluorescent probes confirm that the ZnF₂PMet produces mostly singlet oxygen, whereas F₂PMet generates more hydroxyl radicals as the ROS. F₂PMet is a more effective photosensitizer in vitro than its zinc complex, thus, the final photodynamic effect depends more on the nature of ROS than on the higher cellular uptake.     

Diastereochemically controlled porphyrin dimer formation on a DNA duplex scaffold

DNA-porphyrin conjugates were designed and synthesized for the preparation of the conformationally controlled porphyrin dimer structures constructed on a d(GCGTATACGC)2. Porphyrin derivatives were introduced to the central TATpA sequence where p represents the phosphoramidate for the attachment of the free-base porphyrin (FbP) and zinc-coordinated porphyrin (ZnP), which allows contact of the two porphyrins in the minor groove. The porphyrin dimers were characterized using CD, UV-vis, steady-state, and time-resolved fluorescence spectroscopies, indicating that the porphyrins form face-to-face conformations. Also the co-facial conformation was confirmed by comparison with spectra of the non-self-complementary duplex containing one porphyrin moiety. Introduction of zinc into porphyrin moiety destabilized the duplex formation. Two diastereomers showed different thermal stabilities and affected the conformations of porphyrin dimers. The temperature-dependent assembly and the conformational change of the porphyrin dimer on the duplex DNA were observed in the UV-vis spectra, indicating that the dynamic movement of the porphyrin dimer occurs on the duplex. The results indicate that the porphyrin dimers of DNA-FbP conjugates are overlapped clockwise and are located in the minor groove of the usual B-form DNA backbone. The interaction and conformation of two porphyrin moieties are controlled by the following three factors: (1) temperature change during and after formation of the duplex porphyrins at lower temperature; (2) diastereochemistry of the phosphoramidates where porphyrins are connected via a linker; and (3) zinc ion coordination that destabilizes the interaction of porphyrins as well duplex formation.     

Synthesis,Structural Characterization,and Antimicrobial Activities of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) Complexes of Triazole‐based Azodyes

The synthesis and characterization of new transition metal complexes of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) with 3‐(2‐hydroxynaph‐1‐ylazo)‐1,2,4‐triazole ( HL¹ ) and 3‐(2‐hydroxy‐3‐carboxynaph‐1‐ylazo)‐1,2,4‐triazole ( HL² ) have been carried out. Their structures were confirmed by elemental analyses, thermal analyses, spectral and magnetic data. The IR and ¹H NMR spectra indicated that HL¹ and HL² coordinated to the metal ions as bidentate monobasic ligands via the hydroxyl O and azo N atoms. The UV‐Vis, ESR spectra and magnetic moment data revealed the formation of octahedral complexes [Mn L¹ (AcO)(H₂O)₃] ( 1 ), [Co L¹ (AcO)(H₂O)₃]·H₂O ( 2 ), [Mn L² (AcO)(H₂O)₃] ( 6 ) and [Co L² (AcO)(H₂O)₃] ( 7 ), [Ni L¹ (AcO)(H₂O)] ( 3 ), [Zn L¹ (AcO)(H₂O)]·H₂O ( 5 ), [Ni L² (AcO)(H₂O)] ( 8 ), [Zn L² (AcO)(H₂O)]·10H₂O ( 10 ) have tetrahedral geometry, whereas [Cu L¹ (AcO)(H₂O)₂] ( 4 ) and [Cu L² (AcO)(H₂O)₂]·5H₂O ( 9 ) have square pyramidal geometry.. The mass spectra of the complexes under EI‐con‐ ditions showed the highest peaks corresponding to their molecular weights, based on the atomic weights of ⁵⁵Mn, ⁵⁹Co, ⁵⁸Ni, ⁶³Cu and ⁶⁴Zn isotopes; besides, other peaks containing other isotopes distribution of the metal. Kinetic and thermodynamic parameters of the thermal decomposition stages were computed from the thermal data using Coats‐Redfern method. HL² and complexes 6 – 10 were found to have moderate antimicrobial activities against Staphylococcus aureus (gram positive), Escherichia coli (gram negative) and Salmonella sp bacteria, and antifungal activity against Fusarium oxysporum, Aspergillus niger and Candida albicans. Also, in most cases, metallation increased the activity compared with the free ligand.     

Statistical mixture design development of digestion methods for Oyster tissue using inductively coupled plasma optical emission spectrometry for the determination of metallic ions

The quantitative determination of chemical elements in organic or biological samples is an important analytical problem. Normally the elements to be determined in the organic matrix must be transformed into a simple inorganic form. A digestion method by heating on a block digestor has been developed for the determination of Al, As, Ba, Ca, Cd, Co, Cu, Fe, Mg, Mn, V and Zn in Oyster tissue by ICP OES. A simplex centroid statistical mixture design has been used to study the effects of changing HNO₃, HCl and H₂O₂ reagent proportions on the digestion of these samples. Response surface and principal component analyses show that the species Ca, Cd, Cu, Fe, Mg, Mn and Zn have very similar analytical tendencies under this experiment. By means of mixture modeling maximum recoveries for these ions were predicted using 19%, 18% and 63% of the HCl, HNO₃ and H₂O₂ pseudocomponent mixtures, respectively. This corresponds to 21.4%, 30.8% and 47.8% of the HCl, HNO₃ and H₂O₂ commercial solutions. Furthermore the As, Co and V ions present large recoveries for these mixtures as well. The Al and Ba ion recoveries are seen to be independent of the mixture proportions. The analysis of Oyster tissue reference material (SRM 1566b - NIST) under optimized conditions at the selected wavelengths resulted in ion recoveries between 90% and 100%.     

Isotype Borophosphate MII(C2H10N2)[B2P3O12(OH)] (MII = Mg,Mn, Fe,Ni, Cu,Zn): Verbindungen mit Tetraeder‐Schichtverbänden

Isotypic Borophosphates M^II(C₂H₁₀N₂)[B₂P₃O₁₂(OH)] (M^II = Mg, Mn, Fe, Ni, Cu, Zn): Compounds containing Tetrahedral Layers The isotypic compounds M^II(C₂H₁₀N₂) · [B₂P₃O₁₂(OH)] (M^II = Mg, Mn, Fe, Ni, Cu, Zn) were prepared under hydrothermal conditions (T = 170 °C) from mixtures of the metal chloride (chloride hydrate, resp.), Ethylenediamine, H₃BO₃ and H₃PO₄. The orthorhombic crystal structures (Pbca, No. 61, Z = 8) were determined by X‐ray single crystal methods (Mg(C₂H₁₀N₂)[B₂P₃O₁₂(OH)]: a = 936.81(2) pm, b = 1221.86(3) pm, c = 2089.28(5) pm) and Rietveld‐methods (M^II = Mn: a = 931.91(4) pm, b = 1234.26(4) pm, c = 2129.75(7) pm, Fe: a = 935.1(3) pm, b = 1224.8(3) pm, c = 2088.0(6) pm, Ni: a = 939.99(3) pm, b = 1221.29(3) pm, c = 2074.05(7) pm, Cu: a = 941.38(3) pm, b = 1198.02(3) pm, c = 2110.01(6) pm, Zn: a = 935.06(2) pm, b = 1221.33(2) pm, c = 2094.39(4) pm), respectively. The anionic part of the structure contains tetrahedral layers, consisting of three‐ and nine‐membered rings. The M^II‐ions are in a distorted octahedral or tetragonal‐bipyramidal [4 + 2] (copper) coordination formed by oxygen functions of the tetrahedral layers. The resulting three‐dimensional structure contains channels running along [010]. Protonated Ethylenediamine ions are fixed within the channels by hydrogen bonds.