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.     

Synthesis of non-covalent BODIPY–metalloporphyrin dyads and triads

Boron-dipyrromethenes (BODIPY) containing oxypyridine substituents at 3- and 3,5-positions and metalloporphyrins (Zn(II), Ru(II)) were used to synthesize four non-covalent BODIPY–metalloporphyrin dyads and four BODIPY–metalloporphyrin triads assembled using metal–pyridine ‘N’ interaction. The formation of BODIPY–metalloporphyrin assemblies was confirmed by 1D and 2D NMR methods and X-ray crystal structure obtained for one of the BODIPY–metalloporphyrin dyad. In ¹H NMR, the signals of oxypyridine group(s) of BODIPY unit showed significant upfield shifts supporting the coordination of oxypyridine group of BODIPY unit to metalloporphyrin unit. The NMR study also indicated that Zn(II) porphyrin forms relatively weak BODIPY–Zn(II) porphyrin conjugates, whereas Ru(II) porphyrin forms strong BODIPY–Ru(II) porphyrin conjugates. The X-ray structure solved for BODIPY–Zn(II)porphyrin dyad revealed that the Zn(II) porphyrin coordinated to the BODIPY unit obliquely and the angle between the Zn(II) porphyrin and the pyridyl ring is 70°. The absorption properties of stable BODIPY–Ru(II) porphyrin conjugates showed the overlapping absorption features of both the components and the fluorescence studies indicated that the BODIPY unit emission was significantly quenched on coordination with RuTPP(CO) unit. The electrochemical studies exhibited the features of both BODIPY and metalloporphyrin units in dyads and traids.     

Synthesis of meso-5-azaindolyl-appended Zn(II) porphyrins via Pd-catalyzed annulation

Pd-catalyzed annulation reaction of meso-hexynyl Zn(II) porphyrin with 4-amino-3-iodopyridine efficiently provides meso-3-(5-azaindolyl)-substituted Zn(II) porphyrin as a major product, which assembles to form a slipped cofacial dimer by the complementary coordination of the pyridine moiety to the Zn(II) center. 2-iodoaniline and 2-iodophenol also undergo this [3 + 2] annulation with the meso-hexynyl Zn(II) porphyrin to furnish meso-indolyl- and benzofuranyl-substituted Zn(II) porphyrins, respectively.     

Synthesis of Vinylene-Co,N-Linked Multi(porphyrin)s by the Addition of Free-Base Porphyrins to a C(2)H(2) Complex of Cobalt(III) Porphyrin and Their Oxidative Rearrangement to Vinylene-N,N'-Linked Multi(porphyrin)s

The nucleophilic addition reaction of a pyrrole nitrogen of free-base porphyrins to a pi-complexed acetylene ligand in a cationic Co(III) porphyrin intermediate afforded good yields of vinylene-Co,N'-linked bis(porphyrin)s, (Por)Co(III)-CH=CH-(N-Por)H(2). N-substituted porphyrin free bases are N-vinylated regioselectively at the pyrrole adjacent to the original N-substituted pyrrole in this reaction. Tris- and tetrakis(porphyrin)s have been prepared by reacting a vinylene-N,N'-linked bis(meso-tetraarylporphyrin) with (OEP)Co(III)(H(2)O)(2)ClO(4) (OEP: octaethylporphyrin dianion) and acetylene. The tetrakis(porphyrin) proved to be a 1:1 mixture of C(i)()- and C(2)-symmetric regioisomers. These organometallic Co(III) complexes underwent facile oxidative migration of the Co-bound vinyl group to a porphyrin pyrrole nitrogen when treated with Fe(III) salts or HClO(4) to provide moderate to good yields of Co(II) vinylene-N,N'-linked multi(porphyrin) complexes. (Vinylene-N,N')bis(porphyrin) free bases with combinations of different porphyrins have been obtained by this procedure. The homobinuclear (2Co(II), 2Cu(II), and 2Zn(II)) and heterobinuclear (Co(II)Cu(II) and Co(II)Zn(II)) complexes have been prepared and characterized spectroscopically. The single-crystal X-ray analysis of (CH=CH-N,N')[(OEP)Co(II)Cl][(TPP)Zn(II)Cl] (TPP: meso-tetraphenylporphyrin dianion) showed a face-to-face structure with an average inter-ring separation of 4.39 ? (triclinic P&onemacr;; Z = 2; a = 14.806(4), b = 18.703(10), c = 13.796(3) ?, alpha = 97.69(3), beta = 99.57(2), gamma = 96.74(3) degrees ).     

Synthesis and properties of covalently linked BF2–oxasmaragdyrin–porphyrin dyads and triad

Two covalently linked diphenyl ethyne bridged unsymmetrical dyads containing porphyrin and BF₂–oxasmaragdyrin and Zn(II)porphyrin and BF₂–oxasmaragdyrin units and one covalently linked triad containing Zn(II)porphyrin, porphyrin and BF₂–oxasmaragdyrin units were synthesized by coupling appropriate functionalized macrocycles under Pd(0) coupling reaction conditions. The dyads and triad were freely soluble in common organic solvents and confirmed by ES-MS spectra. 1D and 2D NMR techniques were used to characterize the dyads and triad. Absorption and electrochemical studies of dyads and triad showed the overlapping features of the constituted macrocycles indicating that the macrocycles retain their basic features in the dyads and triad. The BF₂–oxasmaragdyrin absorbs at lower energy and emits strongly in the visible region compared to porphyrin/Zn(II)porphyrin. Thus, BF₂–oxasmaragdyrin acts as energy acceptor and porphyrin/Zn(II) porphyrin act as energy donor in dyads and triad. The steady state and time-resolved fluorescence studies supported an efficient energy transfer from porphyrin/Zn(II)porphyrin to BF₂–oxasmaragdyrin unit in dyads and triad.     

新型水溶性金属卟啉配合物的合成及其光敏性质

本文采用一种新方法合成了三种水溶性极好的新型金属卟啉配合物—5、10、15、20四(对-N-丙磺酸负离子,-N,N-二甲苯胺基)卟啉锌、铜、钴(Zn(Ⅱ)、Cu(Ⅱ)、Co(Ⅱ)TDMAPTPS)和一种新的卟啉,5、10、15、20四(对-N,N-二甲基-N-磺酸负离子苯胺基)双-N-丙磺酸卟啉(TDMAPSPS)。通过红外、紫外、核磁和元素分析等手段对它们进行了表征、确定了它们的结构。采用荧光分析和甲基紫精还原反应研究了它们的光敏性,结果表明,光敏性的强度有如下规律: Zn(Ⅱ)TDMAPTPS>TDMAPSPS>Cu(Ⅱ)TDMAPTPS>Co(Ⅱ)TDMAPTPS。     

Solubility of Tetra(pyrid-3- and 4-yl)porphines and Their Complexes with <Emphasis Type="Italic">d</Emphasis>-Metals in Chloroform and Ethanol

The solubility of 5,10,15,20-tetra(pyrid-3- and 4-yl)porphine isomers and their coordination compounds with d-metals in the temperature range of 298–318 K is studied. Patterns of the dissolving of porphyrin ligands and the metal complexes they form with Co(II), Cu(II), and Zn(II) in chloroform and ethanol depending on the nature of the metal and the position of the nitrogen atom in the pyridyl substituent of the porphyrin molecule are discussed. The thermodynamic parameters of dissolution are calculated for the investigated compounds.     

Time-Resolved Spectroscopic Study on Photoinduced Electron-Transfer Processes in Zn(II)porphyrin–Zn(II)chlorin–Fullerene Triad

Femtosecond time-resolved transient absorption studies have been performed to investigate the photoinduced energy and electron-transfer processes in Zn(II )porphyrin–Zn(II )chlorin–fullerene triad in which energy and oxidation potential gradients are directed along the donor–acceptor-linked arrays. Fast energy transfer (≈450 fs) from photoexcited Zn(II )porphyrin to Zn(II )chlorin was observed upon selective photoexcitation of Zn(II )porphyrin unit in the triad. In a nonpolar solvent such as toluene, the energy transfer from the excited singlet state of Zn(II )chlorin to fullerene occurs and is followed by the formation of an intermediate state with a time constant of nanoseconds, which was attributed to the intramolecular exciplex between Zn(II )chlorin and fullerene. In benzonitrile, on the other hand, the photoexcitation of the triad results in the fast electron transfer (<1 ps) from photoexcited Zn(II )chlorin to fullerene. The generated charge-separated species recombine with a time constant of ≈12 ps. The relatively fast charge separation and charge recombination rates imply that the strong electronic coupling between Zn(II )chlorin and fullerene moieties is probably induced by the folded conformation between Zn(II )chlorin and fullerene moieties which enhances direct through-space interaction between the proximately contacted π systems.     

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.     

Convergent synthesis of meso-ferrocenyl porphyrins for TiO2 sensitization

Electron-donating ferrocenyl moieties have been incorporated into supramolecular carboxyporphyrin architectures Zn(II)-5-ferrocenyl-10,20-bistolyl-15-(4-methylbenzoate)porphyrin (trans-Fc-ZnP-CO₂Me), Zn(II)-5-ferrocenyl-10,15,20-tris(4-methylbenzoate)porphyrin [trans-Fc-ZnP-(CO₂Me)₃], and Zn(II)-5,15-bisferrocenyl-10,20-bis(4-benzoate)porphyrin [trans-Fc₂-ZnP-(CO₂Me)₂] for self-assembly on metal oxide nanoparticles. Efficient and economic synthesis has required a convergent strategy toward reduced symmetry trans-A₂B₂ and trans-AB₂C substitution patterns about the porphyrin macrocycle minimizing the production of porphyrin side products and increasing yields of the target ferrocenylporphyrins. Preliminary spectroscopic data in solution and in the solid state bound to mesoporous TiO₂ films are discussed.     

Kinetic fluorimetric determination of Cu(II) and Zn(II) by their incorporation reactions into a water-soluble porphyrin

Kinetics of incorporation of Cu, Zn, Fe, Co, Ni and Mn divalent ions into coproporphyrin-I in imidazole buffer solution, pH 7.0, has been studied by monitoring the decrease in fluorescence intensity of the free base porphyrin. All reactions followed simple second-order rate law, the rate constants being decreased in the order Zn > Cu > Co > Fe > Mn, Ni. the kinetic fluorimetric method for the determination of Cu(II) and Zn(II) using their incorporation reactions into the porphyrin was developed. Initial rate and fixed-time methods were used to construct calibration graphs over the range 0-1.0 x 10(-5)M of both metals. The analytical characteristics of the method and effect of foreign ions were determined. In the presence of sodium thiosulphate as the masking reagent the determination of micromolar concentrations of Zn in the presence of a 10-fold excess of Cu is possible.     

新型手性酪氨酸卟啉锌对咪唑类客体的分子识别研究

合成了两种新型手性锌卟啉Zn(o-BocTyr)TAPP和Zn(p-BocTyr)TAPP.通过元素分析、紫外可见光谱及核磁共振谱对其性质进行了表征.研究了这两种锌卟啉对咪唑类的分子识别行为,识别的缔合常数顺序均为K(2-MeIm)>K(Im)>K(N-MeIm)>K(2-Et-4-MeIm).同时,采用理论计算和圆二色谱研究了咪唑类小分子在与锌卟啉分子识别时进攻主体位置的变化,这对于研究卟啉分子识别起到一定的作用.     

Excitonic Coupling Strength and Coherence Length in the Singlet and Triplet Excited States of meso–meso Directly Linked Zn(II)porphyrin Arrays

Excitation‐energy transport (EET) phenomena in meso–meso directly linked Zn(II )porphyrin arrays in the singlet and triplet excited states were investigated with a view to electronic coupling strength and coherence length by steady‐state and time‐resolved spectroscopic measurements. To investigate energy transfer in the triplet states, we modified the Zn(II )porphyrin arrays with bromo substituents at both ends. The coupling strength of the Soret bands of the arrays was estimated to be about 2200 cm^?1, and that of the Q bands is about 570 cm^?1. The coherence length in the S₁ state of the Zn(II )porphyrin arrays was determined to be 4–5 porphyrin units, which is comparable to that of the well‐ordered two‐dimensional circular structure B850 in the peripheral light‐harvesting antenna (LH2) in photosynthetic purple bacteria. This indicates that the Zn(II )porphyrin arrays are well suited for mimicking natural light‐harvesting antenna complexes. On the other hand, the rate of energy transfer in the triplet state is estimated to be on the order of 100 μs^?1, and the very weak coupling between the triplet states (ca. 0.003 cm^?1), indicates that the triplet excitation energy is essentially localized on a single porphyrin moiety.     

Synthesis, properties, and crystal structure of a novel anthracene-bridged molybdenum-zinc porphyrin dimer

The synthesis and properties of novel anthracene-bridged porphyrin dimers having an oxomolybdenum(V) porphyrin unit, H(2)(DPA)[Mo(V)O(OMe)] (1) and (DPA)[Mo(V)O(OMe)][Zn(II)(MeOH)] (2), and the relevant monomer porphyrin complexes Mo(V)O(MPP)OMe (3) and Zn(II)(MPP) (4) are presented. An oxomolybdenum(V) unit was introduced into one of the two porphyrins in DPA to give 1, which has a free-base porphyrin unit. By introducing a zinc(II) ion to the free-base part, a mixed-metal complex of 2 was prepared and isolated. The structure of 2 was analyzed by X-ray crystallography (2.(7)/(6)CH(2)Cl(2), triclinic, P(-)1 (no. 2), a = 15.2854(12) A, b = 19.9640(15) A, c = 13.6915(12) A, alpha = 90.968(3), beta = 113.108(4), gamma = 96.501(4), Z = 2, R1 = 9.9, wR2 = 19.2). The structure of 2 demonstrated that a methanol is stably coordinated to the Zn(II) ion with the aid of a hydrogen bond to the methoxo ligand on the Mo(V) ion in the binding pocket of DPA. The electrochemical measurements of 2 suggested that the methanol was kept in the pocket of DPA in solution even at the reduced state of the molybdenum ion.     

Photo processes on self-associated cationic porphyrins and plastocyanin complexes 1. Ligation of plastocyanin tyrosine 83 onto metalloporphyrins and electron-transfer fluorescence quenching

The spectroscopic properties of the self-associated complexes formed between the anionic surface docking site of spinach plastocyanin and the cationic metalloporphyrins, in which the tyrosine 83 (Y83) moiety is placed just below the docking site, tetrakis(N-methyl-4-pyridyl)porphyrin (Pd(II)TMPyP(4+) and Zn(II)TMPyP(4+)), have been studied and reported herein. The fluorescence quenching phenomenon of the self-assembled complex of Zn(II)TMPyP(4+)/plastocyanin has also been discovered. The observed red-shifting of the Soret and Q-bands of the UV-visible spectra, ca. 9 nm for Pd(II)TMPyP(4+)/plastocyanin and ca. 6 nm for the Zn(II)TMPyP(4+)/plastocyanin complexes, was explained in terms of exciton theory coupled with the Gouterman model. Thus, the hydroxyphenyl terminus of the Y83 residue of the self-associated plastocyanin/cationic porphyrin complexes was implicated in the charge-transfer ligation with the central metal atoms of these metalloporphyrins. Moreover, ground-state spectrometric-binding studies between Pd(II)TMPyP(4+) and the Y83 mutant plastocyanin (Y83F-PC) system proved that Y83 moiety of plastocyanin played a critical role in the formation of such ion-pair complexes. Difference absorption spectra and the Job's plots showed that the electrostatic attractions between the cationic porphyrins and the anionic patch of plastocyanin, bearing the nearby Y83 residue, led to the predominant formation of a self-associated 1:1 complex in the ground-state with significantly high binding constants (K = (8.0 +/- 1.1) x 10(5) M(-1) and (2.7 +/- 0.8) x 10(6) M(-1) for Pd(II)TMPyP(4+) and zinc variant, respectively) in low ionic strength buffer, 1 mM KCl and 1 mM phosphate buffer (pH 7.4). Molecular modeling calculations supported the formation of a 1:1 self-associated complex between the porphyrin and plastocyanin with an average distance of ca. 9 A between the centers of mass of the porphyrin and Y83 positioned just behind the anionic surface docking site on the protein surface. The photoexcited singlet state of Zn(II)TMPyP(4+) was quenched by the Y83 residue of the self-associated plastocyanin in a static mechanism as evidenced by steady-state and time-resolved fluorescence experiments. Even when all the porphyrin was complexed (more than 97%), significant residual fluorescence from the complex was observed such that the amplitude of quenching of the singlet state of uncomplexed species was enormously obscured.     

Tetrachelate porphyrin chromophores for metal oxide semiconductor sensitization: effect of the spacer length and anchoring group position

Four Zn(II)-tetra(carboxyphenyl)porphyrins in solution and bound to metal oxide (TiO2, ZnO, and ZrO2) nanoparticle films were studied to determine the effect of the spacer length and anchoring group position (para or meta) on their binding geometry and photoelectrochemical and photophysical properties. The properties of three types of anchoring groups (COOH and COONHEt3) for four Zn(II)-porphyrins (Zn(II)-5,10,15,20-tetra(4-carboxyphenyl)porphyrin (p-ZnTCPP), Zn(II)-5,10,15,20-tetra(3-carboxyphenyl)porphyrin (m-ZnTCPP), Zn(II)-5,10,15,20-tetra(3-(4-carboxyphenyl)phenyl)porphyrin (m-ZnTCP2P), and Zn(II)-5,10,15,20-tetra(3-ethynyl(4-carboxyphenyl)phenyl)porphyrin (m-ZnTC(PEP)P)) were compared. In m-ZnTCPP, m-ZnTCP2P, and m-ZnTC(PEP)P the four anchoring groups are in the meta position on the meso-phenyl rings of the porphyrin macrocycle, thus favoring a planar binding mode to the metal oxide surfaces. The three meta-substituted porphyrin salts have rigid spacer units of increasing length (phenyl (P), biphenyl (P2), and diphenylethynyl (PEP)) between the porphyrin ring and the carboxy anchoring groups, thus raising the macrocycle from the metal oxide surface. All porphyrins studied here, when bound to TiO2 and ZnO, exhibited quenching of the fluorescence emission, consistent with electron injection into the conduction band of the semiconductor. Steady-state UV-vis and fluorescence studies of p-ZnTCPP on insulating ZrO2 showed evidence of aggregation and exciton coupling. This was not observed in any of the meta-substituted porphyrins. The photoelectrochemical properties (IPCE, Voc, and Isc) of the porphyrins bound to TiO2 films in solar cells have been measured and rationalized with respect to the sensitizer binding geometry and distance from the surface.     

β-Octafluorinated tetrakis(ethoxycarbonyl)porphyrin

Tetrakis(alloxycarbonyl)porphyrin and its β-octafluoro-substituted derivatives were synthesized via Lindsey method and transformed to their zinc complexes.Single crystal X-ray structures of corresponding Zn(Ⅱ) porphyrins revealed that β-octafluorination will give more compactness of porphyrin moieties in the crystal structure owing to the hydrogen bonding interactions involving β-fluorine atoms.An unusual six-coordinated Zn(Ⅱ) was found via intramolecular coordination of oxygen atom of meso-substituents with central Zn(Ⅱ).     

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.     

Flexible inner and outer coordination of Zn(II) N-confused porphyrin complex

Tetra- and dinuclear Zn(II) N-confused porphyrin dimers (1, 2) and pyridine-coordinating Zn(II) monomer complex (3) were synthesized, and the ditopic, inner and outer coordination of Zn metal in the dimer complex (1) was demonstrated by X-ray analyses.     

Electrical conduction through linear porphyrin arrays

Electrical conduction measurements were made on two extreme types of directly linked porphyrin arrays by using nanoelectrodes. One type is the directly linked Zn(II)porphyrin arrays, consisting of 48 Zn(II)porphyrin moieties (Z48), and the other type is the completely flat, tape-shaped Zn(II)porphyrin arrays, consisting of eight Zn(II)porphyrin units (T8). The I-V curve for Z48 exhibits the diode-like behavior and the hysteresis depending on the voltage sweep direction presumably due to the conformational heterogeneity arising from the dihedral angle distribution in Z48. On the other hand, the I-V curve for T8 is nearly symmetric without any hysteresis, leading to the higher conductivity and the smaller band gap. These results illustrate that the stronger pi-electron conjugation in T8, as compared with that of Z48, results in better electrical conduction.