Synthesis of covalently linked linear porphyrin triad and tetrad containing different porphyrin sub-units

Covalently linked diarylethyne bridged unsymmetrical porphyrin triad containing ZnN₄, N₄, and N₂S₂ porphyrin sub-units and porphyrin tetrad containing ZnN₄, N₄, N₃S, and N₂S₂ porphyrin sub-units were synthesized over sequence of Pd(0) mediated coupling reactions. The triad and tetrad are freely soluble in all common organic solvents and characterized by ES-MS, NMR, absorption, fluorescence, and electrochemical techniques. The ¹H NMR, absorption, and electrochemical studies indicated a weak interaction between the porphyrin sub-units of porphyrin triad and porphyrin tetrad. The steady state and time-resolved fluorescence studies supported an energy transfer from one end of porphyrin array to the other end. This kind of porphyrin arrays containing different porphyrin sub-units will be useful for molecular electronics applications.     

Hydrogen‐bonded assemblies of 5,10,15,20‐tetrakis(4‐hydroxyphenyl)porphyrin with dimethylformamide,dimethylacetamide and water

The title free base porphyrin compound forms hydrogen‐bonded adducts with N,N‐dimethylformamide, C₄₄H₃₀N₄O₄·4C₃H₇NO, (I), a mixture of N,N‐dimethylformamide and water, C₄₄H₃₀N₄O₄·4C₃H₇NO·H₂O, (II), and a mixture of N,N‐dimethylacetamide and water, C₄₄H₃₀N₄O₄·6C₃H₇NO·2H₂O, (III). Total solvation of the four hydroxy functions of the porphyrin molecules characterizes all three compounds, thus preventing its supramolecular association into extended network architectures. In (I), the asymmetric unit consist of two five‐component adduct species, while in (III), the nine‐component entities reside on centres of inversion. This report provides the first structural characterizations of the free base tetra(hydroxyphenyl)porphyrin. It also demonstrates that the presence of strong Lewis bases, such as dimethylformamide or dimethylacetamide, in the crystallization mixture prevents direct supramolecular networking of the porphyrin ligands via O—H...O—H hydrogen bonds, due to their competing O—H...N(base) interaction with the hydroxy functions. The crystal packing of compounds (I)–(III) resembles that of other hydrogen‐bonding‐assisted tetraarylporphyrin clathrates.     

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.     

Polymeric ionic liquid material‐anchored Mn–porphyrin anion: Heterogeneous catalyst for aerobic oxidation of olefins

P(APTMACl)‐[Mn(TPPS)(OAc)] heterogeneous catalyst system comprised of anionic [Mn(tetrakis(4‐sulfonatophenyl)porphyrin)(OAc)] ([Mn(TPPS)(OAc)]) embedded within cationic cross‐linked polymeric ionic liquid (poly[(3‐acrylamidopropyl)trimethylammonium chloride], p(APTMACl)) hydrogel matrices was used for the selective aerobic oxidation of olefins. P(APTMACl)‐[Mn(TPPS)(OAc)] hydrogel was synthesized by radical polymerization in a solution of cationic APTMACl as an ionic liquid monomer, N,N′‐methylenebisacrylamide as cross‐linking agent, ammonium persulfate as initiator and N,N,N′,N′‐tetramethylmethylenediamine as accelerator in the presence of anionic [Mn(TPPS)(OAc)]. P(APTMACl)‐[Mn(TPPS)(OAc)] was characterized using Fourier transform infrared, diffuse reflectance UV–visible and atomic absorption spectroscopies and scanning electron microscopy. Differential scanning calorimetry was used for measuring the glass transition temperature. Catalytic activity of p(APTMACl)‐[Mn(TPPS)(OAc)] was investigated in the aerobic oxidation of olefins with emphasis on the effect of various parameters such as temperature, catalyst amount, substituent effect, etc. The catalyst was easily recovered from the reaction medium and could be re‐used for another seven runs without significant loss of activity.     

A five‐coordinate iron(III) porphyrin complex including a neutral axial pyridine N‐oxide ligand

While six‐coordinate iron(III) porphyrin complexes with pyridine N‐oxides as axial ligands have been studied as they exhibit rare spin‐crossover behavior, studies of five‐coordinate iron(III) porphyrin complexes including neutral axial ligands are rare. A five‐coordinate pyridine N‐oxide–5,10,15,20‐tetraphenylporphyrinate–iron(III) complex, namely (pyridine N‐oxide‐κO)(5,10,15,20‐tetraphenylporphinato‐κ⁴N,N′,N′′,N′′′)iron(III) hexafluoroantimonate(V) dichloromethane disolvate, [Fe(C₄₄H₂₈N₄)(C₅H₅NO)][SbF₆]·2CH₂Cl₂, was isolated and its crystal structure determined in the space group P. The porphyrin core is moderately saddled and the Fe—O—N bond angle is 122.08 (13)°. The average Fe—N bond length is 2.03 Å and the Fe—ONC₅H₅ bond length is 1.9500 (14) Å. This complex provides a rare example of a five‐coordinate iron(III) porphyrin complex that is coordinated to a neutral organic ligand through an O‐monodentate binding mode.     

Studies of porphyrin zinc compounds intercalated into V<Subscript>2</Subscript>O<Subscript>5</Subscript> xerogel

The intercalation of meso-tetrakis(4-pyridyl)porphyrin zinc, the cationic salts of meso-tetrakis(N-methylpyridinium-4-yl)porphyrin zinc, and zwitterionic meso-tetrakis-[N-(3-sulfonatopropyl)pyridinium-4-yl]porphyrin zinc from aqueous solutions as well as of meso-tetrakis(N-methylpyriclinium-4-yl)porphyrin zinc from pyridine solutions into V₂O₅ xerogel was studied. The intercalation complexes obtained were characterized by X-ray diffraction analysis, TG analysis, IR, and UV reflectance spectroscopy.     

Synthesis of a variety of star‐shaped polybenzamides via chain‐growth condensation polymerization with tetrafunctional porphyrin initiator

A variety of well‐defined tetra‐armed star‐shaped poly(N‐substituted p‐benzamide)s, including block poly(p‐benzamide)s with different N‐substituents, and poly(N‐substituted m‐benzamide)s, were synthesized by using porphyrin‐cored tetra‐functional initiator 2 under optimized polymerization conditions. The initiator 2 allowed discrimination of the target star polymer from concomitantly formed linear polymer by‐products by means of GPC with UV detection, and the polymerization conditions were easily optimized for selective synthesis of the star polybenzamides. Star‐shaped poly(p‐benzamide) with tri(ethylene glycol) monomethyl ether (TEG) side chain was selectively obtained by polymerization of phenyl 4‐{2‐[2‐(2‐methoxyethoxy)ethoxy]ethylamino}benzoate ( 1b ′) with 2 at ?10 °C in the case of [ 1b ′]₀/[ 2 ]₀ = 40 and at 0 °C in the case of [ 1b ′]₀/[ 2 ]₀ = 80. Star‐shaped poly(p‐benzamide) with 4‐(octyloxy)benzyl (OOB) substituent was obtained only when methyl 4‐[4‐(octyloxy)benzylamino]benzoate ( 1c ) was polymerized at 25 °C at [ 1c ]₀/[ 2 ]₀ = 20. On the other hand, star‐shaped poly(m‐benzamide)s with N‐butyl, N‐octyl, and N‐TEG side chains were able to be synthesized by polymerization of the corresponding meta‐substituted aminobenzoic acid alkyl ester monomers 3 at 0 °C until the ratio of [ 3 ]₀/[ 2 ]₀ reached 80. However, star‐shaped poly(m‐benzamide)s with the OOB group were contaminated with linear polymer even when the feed ratio of the monomer 3d to 2 was 20. The UV–visible spectrum of an aqueous solution of star‐shaped poly(p‐benzamide) with TEG side chain indicated that the hydrophobic porphyrin core was aggregated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Synthesis and fluorescence properties of covalently linked homo- and hetero-porphyrin dyads containing meso-tolyl porphyrin and meso-furyl porphyrin sub-units

Three porphyrin building blocks with N₄, N₃S and N₂S₂ cores having three meso-furyl groups and one meso-iodophenyl group were synthesized and characterized. The porphyrin building blocks were used to synthesize six porphyrin dyads such as N₄-N₄, N₃S-N₃S, N₂S₂-N₂S₂, N₄-N₃S, N₄-N₂S₂ and N₃S-N₂S₂ containing meso-tolyl and meso-furyl porphyrin sub-units under mild Pd(0) mediated coupling conditions. Steady state fluorescence studies indicated an efficient energy transfer from the meso-tolyl porphyrin sub-unit to the meso-furyl porphyrin sub-unit in all six dyads. This study supported the argument that the meso-furyl porphyrins can be used as good energy acceptors when meso-aryl porphyrins act as energy donors in their metal free form.     

Spectroscopic properties of meso-thienylporphyrins with different porphyrin cores

The absorption and fluorescence properties of a series of meso-thienylporphyrins with different porphyrin cores (N₄, N₃O, N₃S and N₂S₂ cores) were studied and compared with the corresponding meso-tetraarylporphyrins. The replacement of six-membered phenyl groups with five-membered thienyl groups at meso-positions resulted in red shifts and broadening of absorption and emission bands, low quantum yields and decreased S₁ state lifetimes and the maximum effects were observed for meso-tetrathienylporphyrin with N₂S₂ porphyrin core. Similar observations were noted for the dications of meso-thienylporphyrins compared to the dications of the corresponding meso-tetraarylporphyrins. These results suggest that the replacement of six-membered aryl group with five-membered thienyl groups at meso-positions, the electronic properties of the porphyrin were altered significantly.     

Interaction and photodynamic activity of cationic porphyrin derivatives bearing different patterns of charge distribution with GMP and DNA

The interaction of amphiphilic cationic porphyrins, containing different patterns of meso-substitution by 4-(3-N,N,N-trimethylammoniumpropoxy)phenyl (A) and 4-(trifluoromethyl)phenyl (B) groups, with guanosine 5′-monophosphate (GMP) and calf thymus DNA have been studied by optical methods in phosphate buffer solution. The properties of these synthetic porphyrins were compared with those of representative standard of anionic 5,10,15,20-tetra(4-sulphonatophenyl)porphyrin (TPPS₄⁴⁻) and cationic 5,10,15,20-tetra(4-N,N,N-trimethylammonium phenyl)porphyrin (TMAP⁴⁺). Stable complexes with GMP were found for cationic porphyrins, except for monocationic AB₃⁺. The binding constant (K_GMP  10⁴ M⁻¹) follows the order: A₃B³⁺  ABAB²⁺ > A₄⁴⁺  TMAP⁴⁺. Also, interaction with DNA was observed for all evaluated cationic porphyrins. For these related cationic porphyrins, the binding constant (K_DNA  10⁵ M⁻¹) increases with the number of cationic charges. On the other hand, the photodynamic activity of porphyrins was analyzed in solution of GMP and DNA. Monocationic AB₃⁺ is a less effective sensitizer to oxidize GMP in comparison with the other cationic porphyrins, in agreement with the lack of detected interaction with this nucleotide. The electrophoretic analysis of DNA indicates that photocleavage takes place when the samples are exposed to photoexcited tricationic and tetracationic porphyrins. In the presence of sodium azide the DNA decomposition was diminished. Also, reduction in the DNA photocleavage was observed under anoxic condition, indicating that oxygen is essential for DNA photocleavage sensitized by these cationic porphyrins. In addition, an increase in DNA degradation was not observed in deuteriated water. Therefore, an important contribution of type I photoreaction processes could be occurring in the DNA photodamage sensitized by these cationic porphyrins. These results provide a better understanding of the characteristics needed for sensitizers to produce efficient DNA photocleavage.     

Fluorescence ratiometric pH sensor prepared from covalently immobilized porphyrin and benzothioxanthene

A fluorescence ratiometric sensor for pH determination is described in this paper. The sensor incorporated the pH-sensitive dye meso-5,10,15,20-tetra-(4-allyloxyphenyl)porphyrin (TAPP) as an indicator and a pH-insensitive dye N-(2-methacryloxyethyl)benzo[k,l]thioxanthene-3,4-dicarboximide (MBTD), a benzothioxanthene derivative, as a reference for fluorescence ratiometric measurement. To prevent leakage of the dyes, both were photocopolymerized with acrylamide, hydroxyethyl methacrylate, and triethylene glycol dimethacrylate on the silanized glass surface. The reproducibility and response time of the prepared sensor were sufficient. Most common coexisting inorganic ions and organic compounds did not interfere with pH sensing. In the acidic pH range from 1.5 to 5.0 the fluorescence intensity ratio of the two dyes varied linearly as a function of pH. The sensing membrane was found to have a lifetime of at least one month. The sensor was applied to the analysis of waste water and artificial samples.     

Structural study of a manganese(II) `picket‐fence' porphyrin complex

`Picket‐fence' porphyrin compounds are used in the investigation of interactions of hemes with dioxygen, carbon monoxide, nitric monoxide and imidazole ligands. (Cryptand‐222)potassium chlorido[meso‐tetra(α,α,α,α‐o‐pivalamidophenyl)porphyrinato]manganese tetrahydrofuran monosolvate (cryptand‐222 is 4,7,13,16,21,24‐hexaoxa‐1,10‐diazabicyclo[8.8.8]hexacosane), [K(C₁₈H₃₆N₂O₆)][Mn(C₆₄H₆₄N₈O₄)Cl]·C₄H₈O or [K(222)][Mn(TpivPP)Cl]·THF [systematic name for TpivPP: 5,10,15,20‐tetrakis(2‐tert‐butanamidophenyl)porphyrin], is a five‐coordinate high‐spin manganese(II) picket‐fence porphyrin complex. It crystallizes with a potassium cation chelated inside a cryptand‐222 molecule; the average K—O and K—N distances are 2.83 (4) and 2.995 (13) Å, respectively. All four protecting tert‐butyl pickets of the porphyrin are ordered. The porphyrin plane is nearly planar, as indicated by the atomic displacements and the dihedral angles between the mean planes of the pyrrole rings and the 24‐atom mean plane. The axial chloride ligand is located inside the molecular cavity on the hindered porphyrin side and the Mn—Cl bond is tilted slightly off the normal to the porphyrin plane by 3.68 (2)°. The out‐of‐plane displacement of the metal centre relative to the 24‐atom mean plane (Δ₂₄) is 0.7013 (4) Å, indicating a noticeable porphyrin core doming.     

Oxazolochlorins. 14.

The structure of 8‐oxo‐5,10,15,20‐tetraphenyl‐7‐oxaporphyrin N²⁴‐oxide, C₄₃H₂₈N₄O₃, (4B), shows that N‐oxidation of the pyrrole opposite the oxazolidone group cants the pyrrole out of the mean plane of the chromophore. This also affects the oxazolidone group, which is also slightly canted out. This conformation is qualitatively similar to that of the parent meso‐tetraphenylporphyrin N‐oxide, but dissimilar to that of the porpholactone N‐oxide isomer 8‐oxo‐5,10,15,20‐tetraphenyl‐7‐oxaporphyrin N²²‐oxide, (4A), carrying the N‐oxide at the oxazolidone group. While the degree of canting of the N‐oxidized groups in both cases is comparable (and more pronounced than in the porphyrin N‐oxide case), in (4A) the pyrrolic groups adjacent to the N‐oxidized group are more affected than the opposing group. These differences in the conformational modes may contribute to rationalizing the distinctly different electronic properties of (4A) and (4B).     

Geminal systems. 50. Synthesis and alcoholysis of N-acyloxy-N-alkoxy derivatives of ureas,carbamates, and benzamides

Procedures were developed for the synthesis of N-acyloxy-N-alkoxy derivatives of ureas, carbamates, and benzamides by the reactions of the corresponding N-alkoxy-N-chloro derivatives with sodium carboxylates in MeCN. N-Chloro-N-ethoxy-p-toluenesulfonamide was inert in this reaction. Alcoholysis of N-acyloxy-N-alkoxy derivatives of ureas, carbamates, and tert-alkylamines afforded the corresponding N,N-dialkoxy derivatives, whereas alcoholysis of N-acetoxy-N-ethoxybenzamide gave rise to alkyl benzoates.     

Carbon-13 n.m.r. investigation on the nitrogen methylation of the mono- and diazanaphthalenes

The ¹³C n.m.r. spectra of the N-methylated mono- and diazanaphthalenes have been recorded and analysed. It has been shown that N-methylation as well as N-protonation in cinnoline occur predominantly at the β-nitrogen atom. N-methylation and N-protonation show a similar effect on the ¹³C chemical shifts.     

Anionic polymerization of N-substituted maleimide. II. Polymerization of N-ethylmaleimide

Anionic polymerization of N-ethylmaleimide (N-EMI) was carried out with potassium t-butoxide, lithium t-butoxide, n-butyllithium, and ethylmagnesium bromide as initiators in THF and in toluene. An almost quantitative yield of poly(N-EMI) was obtained with potassium t-butoxide as initiator in THF in a wide range of polymerization temperatures. Initiators possessing lithium as counter cation produced poly(N-EMI) in slightly lower yields and ethylmagnesium bromide gave the polymer only in less than 35% yield in THF. As a polymerization reaction solvent, THF was preferable for the polymerization of N-EMI compared with toluene with respect to polymer yields. Poly(N-EMI) obtained with anionic initiators exerted unimodal molecular weight distribution. From ¹H- and ¹³C-NMR spectra of poly(N-EMI) anionic polymerization of N-EMI with potassium t-butoxide was revealed to proceed at carbon–carbon double bond. t-Butoxide system was found to have a “living” polymerization character, i.e., the observed average degree of polymerization was in good agreement with the one calculated from the initial molar ratio of N-EMI/initiator and the yield of polymer.     

Chiral memory and self-replication study of porphyrin and bilirubin aggregates formed on polypeptide matrices

Porphyrin heteroaggregates composed of meso-tetrakis(N-methylpyridinium-4-yl)porphinatocopper(II) and meso-tetrakis(4-sulfonatophenyl)porphyrin formed in the presence of a polyglutamic matrix possess chiral memory and an ability to self-replicate their supramolecular structures. By means of electronic circular dichroism spectroscopy, it has been shown that the self-replication process is not influenced by changes in pH or ionic strength. The average molecular weight of the polyglutamic matrix used for porphyrin aggregate preparation plays a crucial role with regard to the form of the resulting CD spectrum. In the second part of our study, a complex composed of polylysine and bilirubin as a model system for a structured homoaggregate formed on the chiral matrix has been tested for chiral memory phenomena. The results indicate that the bilirubin homoaggregate shows chiral memory.     

2,3,5,6-tetramethylmorpholine. VI. Cyclization of N-substituted 3,3′-iminobis-2-butanols

The cyclization of N-substituted 3,3′-iminobis-2-butanols to N-substituted 2,3,5,6-tetramethylmorpholines in sulfuric acid is studied. The ring closure seems to be exclusively a normal S_N2-type substitution with partial inversion of configuration before the cyclization. The steric influence of the N-substituents on the S_N2-reaction and on the inversion is discussed.     

1,2,4-Triazoles. V. Nuclear magnetic resonance study of N-Methyl derivatives of 1,2,4-triazoles

The chemical shifts of the N-methyl protons of a number of N-methylated-1,2,4-triazoles were studied. Substitution of methyl and methylthio groups in position 3 causes upfield shifts of the N-methyl signals, while substitution of α-pyridyl, γ-pyridyl, and phenyl groups causes downfield shifts. In 3,5-disubstituted 1,2,4-triazoles, substituents in positions 3 and 5 have additive effects on the chemical shifts of N-methyl groups, so that the chemical shifts of the N-methyl groups of such compounds can be calculated. In this way, it was possible to assign the peaks of mixtures of N-monomethylated derivatives obtained by methylation of 1,2,4-triazoles.     

Quaternary ammonium polyelectrolytes. III. Kinetic studies of amination of chloromethylated polystyrene with tertiary amines

The amination kinetics of benzyl chloride and chloromethylated polystyrene with three tertiary amines were studied: N-2-hydroxyethyl-dimethylamine, N,N-bis(2-hydroxyethyl)-methylamine, and triethylamine in N,N-dimethylformamide. The amination of chloromethylated polystyrene takes place with two reaction rate constants K₁ and K₂. K₂ is higher than K₁; hence there is a self-accelerating effect. This phenomenon is due to the influence of the positive electrostatic field of the macroion chain on amines that are nucleophilic reactants. The magnitude of the self-accelerating effect given by the K₂/K₁ ratio depends on the substituent volume of the nitrogen atom of the amine molecule.