Meso-tetraphenylporphyrin Derivatives Research Articles

Some Terminally Alkenyl-substituted Porphyrins: Synthesis and Attempts of Heck Reaction Leading to Porphyrin–Azulene Dyads

: The synthesis of meso-tetraphenylporphyrin derivatives, double functionalized in one of the phenyl rings (with a nitro group and carbon substituents), is described. 5-(4- Nitroaryl)-10,15,20-triarylporphyrinates react, in the presence of a base (t-BuOK), with carbanions containing a leaving group at the carbanionic center to give products of substitution of hydrogen at ortho-position to the nitro group via vicarious nucleophilic substitution scheme. Their alkylation with allyl bromide or 4-bromobut-1-en (t-BuOK/DMF, at 0-5°C) leads to porphyrins bearing side alkyl chain with a terminal double bond in yields of up to 82%. The above-mentioned double-substituted intermediates are very convenient substrates for Heck cross-coupling reaction. In this study, the synthesis of porphyrin–azulene dyads is reported. In some cases, the formation of highly conjugated systems is observed, with moderate yield. Their structures are interesting from both the porphyrin and azulene point of view.

Substituent Effects in the Photophysical and Electrochemical Properties of Meso-Tetraphenylporphyrin Derivatives.

Porphyrins were identified some years ago as a promising, easily accessible, and tunable class of organic photoredox catalysts, but a systematic study on the effect of the electronic nature and of the position of the substituents on both the ground-state and the excited-state redox potentials of these compounds is still lacking. We prepared a set of known functionalized porphyrin derivatives containing different substituents either in one of the meso positions or at a β-pyrrole carbon, and we determined their ground- and (singlet) excited-state redox potentials. We found that while the estimated singlet excited-state energies are essentially unaffected by the introduction of substituents, the redox potentials (both in the ground- and in the singlet excited-state) depend on the electron-withdrawing or electron-donating nature of the substituents. Thus, the presence of groups with electron-withdrawing resonance effects results in an enhancement of the reduction facility of the photocatalyst, both in the ground and in the excited state. We next prepared a second set of four previously unknown meso-substituted porphyrins, having a benzoyl group at different positions. The reduction facility of the porphyrin increases with the proximity of the substituent to the porphine core, reaching a maximum when the benzoyl substituent is introduced at a meso position.

Shielding Effects in 1H NMR Spectra of Halogen-Substituted meso-Tetraphenylporphyrin Derivatives

Shielding Effects in 1H NMR Spectra of Halogen-Substituted meso-Tetraphenylporphyrin Derivatives

Hyperporphyrin effect on oxygen sensitivity of free meso-tetraphenylporphyrins

A series of dyes; three symmetric free meso-tetraphenylporphyrins, bearing phenylacetylide (H2-TPA), hexyloxy (H2-OHex) or without peripheral substituent (H2-TPP) were chosen as luminophore to explore the effect of meso-substitution on the oxygen sensing ability. These dyes were incorporated into poly(trimethylsilylpropyne) [poly(TMSP)], polymethylmethacrylate (PMMA) and silicone matrices along with additives such as perfluorododecanoic acid (PFC) to improve the oxygen sensitivity as well as ionic liquid to favor the microfiber preparation by electrospinning. The pH of the medium is affected by the composition of the cocktail, a non-trivial effect which induce protonation of the free meso-tetraphenylporphyrin derivatives bearing electron donor (H2-OHex) and withdrawing substituents (H2-TPA), which results in absorbance and emission spectroscopic modifications called elsewhere hyperporphyrin effect. Spectrophotometric titrations were carried out by using HClO4 in THF solution and PFC in [poly(TMSP)]-based thin film to study the hyperporphyrin effect of H2-TPA, H2-OHex and H2-TPP showing the influence of the substituent on the pKa of the inner nitrogen's. The ratio of PFC/dyes optimization was prospected and the influence of the pH/protonation on the steady-state oxygen sensitivity was studied.

Nonlinear optical properties tuning in meso-tetraphenylporphyrin derivatives substituted with donor/acceptor groups in picosecond and nanosecond regimes.

meso-Tetraphenylporphyrin (TPP) and its two substituted derivatives (meso-tetrakis(4-cyanophenyl)porphyrin [TPP(CN)4] and meso-tetrakis(4-methoxyphenyl)porphyrin [TPP(OMe)4]) were synthesized. Their nonlinear absorption and refraction properties were studied using the Z-scan technique in the picosecond (ps) and nanosecond (ns) regimes. The open aperture Z-scan results reveal that TPP and TPP(CN)4 display an identical reverse saturable absorption (RSA) character in the ps and ns regimes. While TPP(OMe)4 exhibits a transition from saturable absorption (SA) to RSA in the ps regime and a typical RSA character in the ns regime. The closed aperture Z-scan results show that TPP(CN)4 and TPP(OMe)4 have regular enhancement of the magnitude of nonlinear refraction as compared to their parent TPP in both the ps and ns regimes. In addition, the second-order molecular hyperpolarizabilities (γ) of these three porphyrins are calculated, and the γ values of TPP(CN)4 and TPP(OMe)4 are remarkable larger than that of TPP. The introduction of the electron-withdrawing group CN and the electron-donating group OMe into TPP has enhanced its nonlinear refraction and γ value, and tuned its nonlinear absorption (TPP(OMe)4), which could be useful for porphyrin-related applications based on the desired NLO properties.

Synthesis, spectroscopy, and photophysics of porphyrins attached to gold nanoparticlesviaone or two linkers

Four new meso-tetraphenylporphyrin derivatives were prepared, singly and doubly substituted with thiocarbamate and thioacetate groups. These compounds were subsequently attached to gold nanoparticles suspended in chloroform. Very different kinetics of the attachment were revealed; the process was much faster for the thiocarbamate derivatives. Spectral, photophysical, and scanning electron microscopy studies revealed large differences in the morphology of the gold–porphyrin systems. The porphyrins with one linker attach to single nanoparticles, whereas the dual linker derivatives induce formation of aggregates, characterized by readily detectable Raman signals. A "hot-spot" type structure is proposed for the latter, with the porphyrin bridging two gold nanoparticles.

Controlled self-assembly and photovoltaic characteristics of porphyrin derivatives on a silicon surface at solid–liquid interfaces

Two meso-tetraphenylporphyrin (H2TPP) derivatives with different central metal ions, namely ZnTPP, CuTPP, were synthesized, and characterized by a series of spectroscopic methods. Their self-assembly behaviors in mixed solvents without surfactant were systematically investigated. The morphology of the thus produced nanoarchitectures could be efficiently controlled. Nanoslices can be manufactured when a volume of cyclohexane is involved, octahedrons can be produced when a mixed solvent of chloroform and isopropanol is employed, while four-leaf clover-shaped structures can be produced with a large volume of methanol injected. The nanostructures have been characterized by electronic absorption, scanning electron microscopy (SEM) and photoelectric conversion techniques. The internal structures of the nanostructures are well described by XRD. The nanostructures exhibit a power conversion under illumination intensity of 2.3 mW cm(-2). The present result appears to represent an effort toward controlling the morphology of self-assembled nanostructures of porphyrin derivatives via synthesis through introduction of metal-ligand and solvent interaction. Nevertheless, the fundamental study will be helpful to understand photoinduced energy/charge transport in an organic interface and this might also serve as promising building blocks for nanoscale power sources for potential application in solar energy technologies and organic electronics and optoelectronics.

Self-Terminating Protocol for an Interfacial Complexation Reaction in Vacuo by Metal–Organic Chemical Vapor Deposition

The fabrication and control of coordination compounds or architectures at well-defined interfaces is a thriving research domain with promise for various research areas, including single-site catalysis, molecular magnetism, light-harvesting, and molecular rotors and machines. To date, such systems have been realized either by grafting or depositing prefabricated metal-organic complexes or by protocols combining molecular linkers and single metal atoms at the interface. Here we report a different pathway employing metal-organic chemical vapor deposition, as exemplified by the reaction of meso-tetraphenylporphyrin derivatives on atomistically clean Ag(111) with a metal carbonyl precursor (Ru3(CO)12) under vacuum conditions. Scanning tunneling microscopy and X-ray spectroscopy reveal the formation of a meso-tetraphenylporphyrin cyclodehydrogenation product that readily undergoes metalation after exposure to the Ru-carbonyl precursor vapor and thermal treatment. The self-terminating porphyrin metalation protocol proceeds without additional surface-bound byproducts, yielding a single and thermally robust layer of Ru metalloporphyrins. The introduced fabrication scheme presents a new approach toward the realization of complex metal-organic interfaces incorporating metal centers in unique coordination environments.

Synthesis of Highly Substituted Nitro/Ha­lo-meso-tetraaryl­porphyrins by Tandem Cyclocondensation/Aromatic Electrophilic Nitration Reactions

Synthesis of highly functionalized nitro/halo-5,10,15,20-tetraaryl porphyrins is described. meso-Tetraphenylporphyrin derivatives (halo-substituted in meso-phenyl rings; with F, Cl, Br, and I), in the reaction with fuming yellow nitric acid (d = 1.52), result in the formation of mono-, di-, tri-, and even tetranitro-substituted porphyrins (with summary yields of 28–81%), depending on the reaction temperature (0 °C to 5 °C or at r. t.), amounts of the acid used, and reaction time. In some cases moderate selectivity was observed. The starting halo-substituted meso-tetraarylporphyrins were prepared in the cyclocondensation reaction of pyrrole with the respective aromatic aldehydes (usually carried out according to known procedures). By this route, the preparation of the synthetic porphyrins (bearing up to ten halo-/ nitro-substituents) was demonstrated.

DFT/TD-DFT study of solvent effect as well the substituents influence on the different features of TPP derivatives for PDT application

Spectral characteristics study of meso-tetraphenylporphyrin derivatives (TPP1 and TPP2) used as photosensitizers for utilization in photodynamic therapy (PDT) has been performed by density functional theory (DFT) and time dependent DFT (TD-DFT) calculations at B3LYP/6-31G(d) level of theory using PCM solvation model. The geometrical parameters of porphyrins have been studied for ground and excited-state geometry to deduce the influence of various substituents as well as solvent effect on the deformation of porphyrin ring. Two theoretical approaches – linear response (LR) and external iteration (EI) – have been performed to replicate absorption and fluorescence emission spectra. Experimental and theoretical investigations have shown that EI method reproduces the absorption energies very well for both singlet–singlet and triplet–triplet transitions, whereas the LR approach is more coherent with experimental fluorescence emission spectra. Spectral features and HOMO–LUMO band gap analysis have shown that TPP1 can be more useful in PDT. Calculations have revealed that two the highest occupied and two the lowest unoccupied molecular orbitals are responsible for the Q-band absorption and are located mainly on the porphyrin ring. In order to verify the substituent effect on the activity of tested compounds in their ground and excited states, the molecular electrostatic potential surfaces have been analyzed.

Determination of explosives based on novel type of sensor using porphyrin functionalized carbon nanotubes

The hydroxide of meso-tetraphenylporphyrin derivatives functionalized carbon nanotubes (CNTs) was fabricated in our research to explore the interaction between porphyrin and explosive. It was turned out that in the formation of grid porphyrin film, carbon nanotubes as a cruciul base materials promoted the electron transfer rate. Most of important, the results also showed that the electrochemical response was enhanced through increasing the number of -OH substitution in porphyrin. Such information provides the platform for a practical strategy for rational design of the sensor of explosives.

Diprotonation process of meso-tetraphenylporphyrin derivatives designed for Photodynamic Therapy of cancers: From Multivariate Curve Resolution to predictive QSPR modeling

Tetrapyrrole rings possess four nitrogen atoms, two of which act as Bröndsted bases in acidic media. The two protonation steps occur on a close pH range, particularly in the case of meso-tetraphenylporphyrin (TPP) derivatives. If the cause of this phenomenon is well known – a protonation-induced distortion of the porphyrin ring – data on stepwise protonation constants and on electronic absorption spectra of monoprotonated TPPs are sparse. A multivariate approach has been systematically applied to a series of glycoconjugated and hydroxylated TPPs, potential anticancer drugs usable in Photodynamic Therapy. The dual purpose was determination of protonation constants and linking substitution with basicity. Hard-modeling version of MCR-ALS (Multivariate Curve Resolution Alternating Least Squares) has given access to spectra and distribution profile of pure components. Spectra of monoprotonated species (H 3TPP +) in solution resemble those of diprotonated species (H 4TPP 2+), mainly differing by a slight blue-shift of bands. Overlap of H 3TPP + and H 4TPP 2+ spectra reinforces the difficulty to evidence an intermediate form only present in low relative abundance. Depending on macrocycle substitution, p K values ranged from 3.5 ± 0.1 to 5.1 ± 0.1 for the first protonation and from 3.2 ± 0.2 to 4.9 ± 0.1 for the second one. Inner nitrogens’ basicity is affected by position, number and nature of peripheral substituents depending on their electrodonating character. p K values have been used to establish a predictive Multiple Linear Regression (MLR) model, relying on atom-type electrotopological indices. This model accurately describes our results and should be applied to new TPP derivatives in a drug-design perspective.

Meso-tetraphenyl porphyrin derivatives: The effect of structural modifications on binding to DMPC liposomes and albumin

Three series of glycoconjugated and hydroxylated derivatives of 5,10,15,20- meso-tetraphenyl porphyrin (TPP) were studied in order to evaluate the effect of a porphyrin structure on its binding to dimyristoylphosphatidylcholine (DMPC) liposomes and to human serum albumin (HSA). The studied derivatives have been developed as potent photosensitizers for photodynamic therapy (PDT) of cancers. Steady state and time resolved fluorescence emission spectroscopy, Stern–Volmer quenching and fluorescence anisotropy were used for this evaluation. The lipophilicity of the compounds has been deduced from their retention time in reverse phase liquid chromatography. The results demonstrated that the more polar glycoconjugated compounds presented limited aggregation in aqueous media and very rapid binding kinetics to DMPC liposomes and HSA. Derivatives having intermediate or high hydrophobicity showed extensive auto-association in aqueous media and as a consequence slow association kinetics. The strength of porphyrin binding to DMPC liposomes also depended on their lipophilicity and was lower for the polar glycoconjugated analogues. The highest affinity for liposomes was observed for hydroxylated derivatives with intermediate lipophilicity. In contrast, the highest binding constant for albumin was observed for a polar tetra-glycoconjugated analogue. The depth of penetration into the phospholipid bilayer did not appear to be directly related to the global hydrophobicity of the compounds, but depended more on the number of apolar, non-substituted phenyl groups grafted to a tetrapyrrolic macrocycle. Furthermore, liposome–albumin competition studies revealed that the porphyrins were always mainly partitioned into the phospholipid bilayer.

Mitochondria-targeting properties and photodynamic activities of porphyrin derivatives bearing cationic pendant

Four meso-tetraphenylporphyrin derivatives bearing either triphenylphosphonium ion-(P1 and P2) or triethylammonium ion-(P3 and P4) terminated alkoxy group at either para-(P1 and P3) or meta-(P2 and P4) position of one meso-phenyl group were designed and synthesized. P1-P4 show similar absorption and fluorescence emission spectra and (1)O(2) quantum yields. The more lipophilic nature of triphenylphosphonium ion over triethylammonium ion renders P1 and P2 higher octanol/water partition coefficients than P3 and P4. Confocal fluorescence microscopy proved that P1-P4 are all mitochondria-targeting. MTT assay showed that P1-P4 presented significant phototoxicity at the concentrations that dark toxicity is negligible towards human breast cancer cell line MCF-7 cells, displaying their application potential in PDT.

Synthesis of cationic β-vinyl substituted meso-tetraphenylporphyrins and their in vitro activity against herpes simplex virus type 1

An easy route to cationic β-vinyl substituted meso-tetraphenylporphyrin derivatives is described. Two novel compounds were tested in vitro for their antiviral photoactivity against herpes simplex virus type 1. One of these compounds exhibited a significant activity, reaching 99% of virus inactivation after 15 min of photoactivation.

Synthesis of Stably Water-Soluble Gold Nanoparticles Protected by Porphyrin-Thiol Derivative

Meso-tetraphenylporphyrin derivative having four thioacetyl groups was synthesized using Lindsay's method. Monodisperse small gold (Au) nanoparticles passivated by the synthesized ligand were prepared by a liquid phase synthesis. The nanoparticles were extremely stable and can be homogeneously dispersed in basic aqueous solution. [DOI: 10.1380/ejssnt.2005.30]

UV−Vis Spectrophotometric Titrations and Vibrational Spectroscopic Characterization of meso-(p-Hydroxyphenyl)porphyrins

Sequentially spectrophotometric titrations by sodium hydroxide of meso-tetraphenylporphyrin derivatives bearing one, two, three, or four p-hydroxyl groups result in new types of spectra. The strong new bands appear in the visible region with splitting or broadening of the Soret band and its significant loss of oscillator strength. To understand the molecular origin of these phenomena, the Resonance Raman (RR) and Fourier Transform Infrared (FTIR) experiments are carried out. The results demonstrate that the charges of the deprotonated para-hydroxy substituted meso-tetraphenylporphyrins are localized on the substituents, not delocalized into the π system of the porphyrin macrocycles and that the ground states of the macrocycles remain essentially unperturbed. Both the related behavior of diprotonated tetrakis(p-(dimethylamino)phenyl) porphyrin and protonated Schiff base porphyrins show that the new bands considered as hyperporphyrin spectra are due to π(phenoxide anion) → π*(porphyrin) transitions, where π...

Modulation of porphyrin binding to serum albumin by pH.

In this study, we show that the difference in acidity of functional groups in porphyrin photosensitizers provides a meaningful avenue to achieve differential localization and retention of porphyrins in tissues and cells, and in the end could be a positive factor in the photodynamic treatment of cancer (PDT). We have demonstrated that meso-tetraphenylporphyrin derivative with four phosphonate (bond P(double bond O)(bond OH)(2)) moieties exists in aqueous solutions mainly in four forms that differ by a degree of protonation of the porphyrin ring and ionization of the phosphonate group. It is shown that each porphyrin form has different affinities toward the model protein (bovine serum albumin, BSA). Thus pH of the medium significantly modulates the affinity of the phosphonate porphyrin toward BSA. At lower pH (pH 6.0), the phosphonate porphyrin and BSA form a complex with affinity constant of K(b)=6.9 x 10(5) M(-1), while at pH 7.0 the K(b)=6.1 x 10(5) M(-1). At pH 8.0 the association is significantly lower. Because cancerous cells have generally lower pH (pH approximately 6.9) compared to healthy cells (pH approximately 7.4), the pH of such cells could be a decisive factor for cellular retention of the porphyrin in the form of an associate with intracellular proteins. Moreover, we have also demonstrated that the protonation/deprotonation equilibria do not negatively affect the photophysical properties or ability of phosphonate porphyrin to generate singlet oxygen.

Localization and photodynamic efficacy of two cationic porphyrins varying in charge distributions.

Two meso-tetraphenylporphyrin derivatives bearing adjacent: 5,10-di[4-(N-trimethylaminophenyl)-15,20-diphenylporphyrin (DADP-a) or opposite: 5,15-di[4-(N-trimethylaminophenyl)-10,20-diphenylporphyrin (DADP-o) cationic-N-(CH3)3+ groups on two of the para-phenyl positions were examined with regard to photodynamic properties as a function of charge distribution. The two adjacent positive charges in the DADP-a structure result in a molecular distortion (asymmetry), likely from electrostatic repulsion. This could be responsible for the unusual interaction of this compound with some solvents and detergent micelles. In contrast, DADP-o is a much more symmetric molecule. In a cellular environment, fluorescence spectra of the two agents were essentially identical. Subcellular localization played a major role in photodynamic efficacy. DADP-a localized in mitochondria, and irradiation of photosensitized cells (640-650 nm) resulted in a rapid loss of the mitochondrial membrane potential (delta(psi)m), usually a prelude to apoptotic cell death. In contrast, DADP-o localized in lysosomes, and extensive lysosomal photodamage was observed after irradiation. Both steady-state accumulation levels and absorbance spectra favored DADP-o, but the light dose required for a 90% cell kill was two-fold greater for DADP-o than for DADP-a, at a constant extracellular sensitizer concentration. These data indicate that, on a photons/cell basis, DADP-a was five-fold more efficacious. Fluorescence emission spectra in different solvents and detergents demonstrated a tendency for DADP-a association. We interpret these results to indicate partition of both drugs to membrane loci, with mitochondriabeing the more lethal site for photodamage.

Anticorrosive Lipid Monolayers with Rigid Walls around Porphyrin-Based 2 nm Gaps on 20 nm Gold Particles

A meso-tetraphenylporphyrin derivative with two butanethiol and two carboxylate groups on opposite phenyl substituents was first covalently bound to citrate gold particles by a self-assembly procedure. In a second self-assembly step the remaining areas on the gold surface were covered with a monolayer of a bolaamphiphile (“bola”) containing a hydrosulfide end group for the attachment to gold and a triethylene glycol (TEG) end group for solubilization in water as well as in toluene. Bolas with octyl ends for dissolution only in toluene and with chiral gluconamide ends for water were also synthesized and applied. Two central secondary amide functions separated by 10 methylene units formed hydrogen bond chains within the monolayer and made it impermeable for cyanide ions. The porphyrin bottom of the water-filled gaps did not allow the passage of cyanide either. The holey membrane provided a complete protection against corrosion of the gold particles by 0.1 M cyanide in the bulk water. The porphyrin molecules on the bottom of the 2.2 nm wide gaps showed a weak fluorescence. It was quenched quantitatively by a tetracationic manganese porphyrinate, which fitted exactly into the gaps. A tetracationic porphyrin with a width of 3.4 nm caused no fluorescence quenching. The gaps thus have the uniform size of a monomeric porphyrin, and no domain formation was apparent. The same gaps with walls made of octadecanethiol did not discriminate between the two porphyrins of different size, both causing quantitative quenching. 1,2-trans-Cyclohexanediol or tyrosine were irreversibly immobilized within the gaps at pH 7 and stopped the entrance of the fitting porphyrin in both the rigid and the flexible gaps. The citrate gold particles thus proved to be smooth enough to allow the formation of well-defined gaps. It was also shown that 800 mg of gold colloid carries about 20 mg of membrane and gap material, which is enough for their characterization by solid-state NMR spectroscopy.