H2T PP Research Articles

Molecular Engineering Design of Enhanced Donor-Acceptor Therapeutic Reagent for Efficient Image-Guided Photodynamic Therapy.

The greatest barrier to the further development and clinical application of tumor image-guided PDT, is the inconsistency between the fluorescence intensity and the singlet oxygen generation yield of the photosensitizer under light excitation. Here, a novel donor-acceptor (D-A) system wa s designed from the point of molecular selection by wrapping a classical porphyrin molecule (H2 TPP) as an acceptor into conjugated polymer (ADS254BE) as a donor through fluorescence resonance energy transfer mechanism, which exhibits bright red emission centered at 650nm (Quantum yield, 0.12), relatively large Stoke shift of 276nm, enhanced singlet oxygen generation rate of 0.73, and excellent photostability. The investigations on distribution and killing effect of nanomaterials in cancer cells revealed that ADS254BE/H2 TPP NPs can accumulate in the cytoplasm for imaging while simultaneously producing a large amount of singlet oxygen to remarkably kill cancer cells, which could be used for real-time image-guided PDT. In the xenograft tumor model, real-time imaging and long-term tracing in tumor tissue with ADS254BE/H2 TPP NPs disclosed that the growth of lung cancer in mice could be effectively inhibited during in-situ imaging. From the standpoint of molecular engineering design, this work provides a feasible strategy for novel D-A systems to improve the development of image-guided PDT. This article is protected by copyright. All rights reserved.

The fabrication of albumin- Tetraphenylporphyrin -metronidazole nanosystem as potential photosensitizers/radiosensitizers for radiation-induced cancer therapy

Breast cancer is the second leading cause of cancer death in women after lung cancer. In the context of cancer therapy, chemotherapy regarded as the most common method of treatment, but besides this beneficial modality, radiation therapy (RT) is used as a supplementary or palliative treatments. In this regard, we aimed at preparing albumin- Tetraphenylporphyrin -metronidazole nanosystem (BSA-Met- H2T(4-SO2)PP NPs) as an effective photo/radiosensitizer along with RT to tackle breast cancer. Accordingly, the synthesized nanosystems were analyzed by various characterization techniques such as dynamic light scattering (DLS), fourier transform infrared spectroscopy (FT-IR), UV-vis, and proton nuclear magnetic resonance (1HNMR), also transmission electron microscopy (TEM) technique was used to determine the morphology and size of fabricated nanosystems. Moreover, the biosafety of developed nanosystems were ascertained using LD50 and hemolysis assay. Based on DLS measurements the average size and polydispersity index of fabricated nanosystems were about 190 nm and 0.36, respectively. The BSA-Met-H2T(4-SO2)PP NPs showed pH-dependent drug release behavior. The results showed that the drug loading (DL) for metronidazole and Tetraphenylporphyrin were 3.406% and 13.586%, respectively. Both hemolysis and LD50 confirmed the biosafety of the BSA-Met-H2T(4-SO2)PP NPs. Finally, MTT assay revealed that the prepared nanoparticles exhibited great anti-cancer activity upon radiation and light against 4T1 cancer cells. Overall, our findings suggest that PPHN-MET NPs may be promising candidates for the effective radiation/or light-induced cancer therapy.

Supercapacitor based on graphene oxide/tetra(para-aminophenyl)porphyrin/Nylon 66 composite electrode

The study of the graphene oxide (GO)/tetra-(para-aminophenyl)porphyrin (H2T(p-NH2)PP)/Nylon 66 (Nylon) composite as an electrochemical supercapacitor was subjected to electrochemical impedance spectroscopy, cyclic voltammetry and galvanostatic charging-discharging measurement techniques, in a 1 M H2SO4 electrolytic solution. The results of the analysis showed an increase in the specific capacity of the system by modifying the percentage by weight of GO to 60%, 80% and 90%, making this effect more evident after performing an activation in NaOH, due to the increase in surface area of the electrode, as well as interactions with the center of the porphyrin macrocycle, reaching maximum specific capacitance values of 328 F/g. This system combines the formation of the electrochemical double layer and pseudocapacitor phenomena as energy storage mechanisms.

Reverse Arene Sandwich Structures Based upon π‐Hole⋅⋅⋅[MII] (d8 M=Pt, Pd) Interactions, where Positively Charged Metal Centers Play the Role of a Nucleophile

The complexes [Pt(tpp)] (H2 tpp=tetraphenylporphyrin), [M(acac)2 ] (M=Pd, Pt, Hacac=acetylacetone), and [Pd(ba)2 ] (Hba=benzoylacetone) were co-crystallized with highly electron-deficient arene systems to form reverse arene sandwich structures built by π-hole⋅⋅⋅[MII ] (d8 M=Pt, Pd) interactions. The adduct [Pt(tpp)]⋅2 C6 F6 is monomeric, whereas the diketonate 1:1 adducts form columnar infinity 1D-stack assembled by simultaneous action of both π-hole⋅⋅⋅[MII ] and C⋅⋅⋅F interactions. The reverse sandwiches are based on noncovalent interactions and calculated ESP distributions indicate that in π-hole⋅⋅⋅[MII ] contacts, [MII ] plays the role of a nucleophile.

One-Dimensional Porphyrin-Fullerene (C60 ) Assemblies: Role of Central Metal Ion in Enhancing Ambipolar Mobility.

One-dimensional (1D) nanostructures of π-conjugated molecules exhibiting excellent charge carrier mobilities have attracted much interest for use in organic electronic devices. Although it is tedious to form such structures, the availability of highly delocalized electron and hole carriers in these donor (D)-acceptor (A) coassemblies realize ambipolar charge transport. Here we demonstrate the use of a simple solution casting method to create an ambipolar donor-acceptor single-crystalline assembly. 1D assemblies of 5,10,15,20-tetraphenylporphyrins (H2 TPP, ZnTPP) and fullerene (C60 ) exhibit high ambipolar mobility in the range of 0.8-3.4 cm2 Vs-1 for electrons and holes with high ON/OFF ratio and low threshold voltage. A direct experimental proof for the pivotal role of the central Zn2+ in tetraphenyl porphyrin, which enables a strong D-A charge transfer interaction in the cocrystal and thereby induces electron (1.35 cm2 Vs-1 ), hole (3.42 cm2 Vs-1 ) mobilities, the highest reported for two component D-A assemblies using solution casting, is demonstrated.

An Organic Mixed-Valence Ligand for Multistate Redox-Active Coordination Networks.

The multistate redox-active/multi-interactive ligand 5,5',8,8'-tetra(4-pyridyl)-2,2'-(1,4-phenylene)bis-1H-perimidine (H2 TPP) was designed and synthesized. H2 TPP undergoes four one-electron oxidation steps, and was used for the preparation of a multistate redox-active coordination network in a solid-liquid interface reaction using molten Cd2+ salts. The multiple redox states of H2 TPP were confirmed spectroscopically by stepwise four-electron oxidation. Spectroscopic analysis indicated that the mixed-valence states of the ligand are class II on the UV/Vis/NIR timescale and borderline class II/class III on the ESR timescale.

Porphyrin-Based Symmetric Redox-Flow Batteries towards Cold-Climate Energy Storage.

Electrochemical energy storage with redox-flow batteries (RFBs) under subzero temperature is of great significance for the use of renewable energy in cold regions. However, RFBs are generally used above 10 °C. Herein we present non-aqueous organic RFBs based on 5,10,15,20-tetraphenylporphyrin (H2 TPP) as a bipolar redox-active material (anode: [H2 TPP]2- /H2 TPP, cathode: H2 TPP/[H2 TPP]2+ ) and a Y-zeolite-poly(vinylidene fluoride) (Y-PVDF) ion-selective membrane with high ionic conductivity as a separator. The constructed RFBs exhibit a high volumetric capacity of 8.72 Ah L-1 with a high voltage of 2.83 V and excellent cycling stability (capacity retention exceeding 99.98 % per cycle) in the temperature range between 20 and -40 °C. Our study highlights principles for the design of RFBs that operate at low temperatures, thus offering a promising approach to electrochemical energy storage under cold-climate conditions.

Nylon/Porphyrin/Graphene Oxide Fiber Ternary Composite, Synthesis and Characterization

This research was based on the manufacture of new composite materials that offer technological possibilities in the development of new devices with greater efficiency. Electrospinning was used to form nylon 66/-tetra-(para-aminophenyl) porphyrin (H2T(p-NH2)PP)/graphene oxide (GO) composite film. Graphene oxide coatings were obtained from graphite, through mechanical exfoliation followed by calcination and ultrasonic agitation in an oxidant solution. These samples were characterized under SEM, FTIR, Raman spectroscopy, UV-vis and R-X techniques. On the other hand, H2T(p-NH2)PP was synthesized in two steps process by the Rothemun reaction and the Adler Method and it was integrated within nylon polyamide fibers by direct addition of a hexamethylenediamine/adipoyl chloride reactant mixture. The polymerization of the nylon/H2T(p-NH2)PP species occurs in such a way that it starts or ends on the four peripherals-NH2 groups, connected and located in the same molecular plane of H2T(p-NH2)PP, forming nylon chains at the periphery of the macrocycle. The association of GO with nylon/H2T(p-NH2)PP fibers is performed by dipole-dipole interaction and hydrogen bonding. To take advantage of the properties of these materials, they were combined as a ternary composite.

Engineering Chemically Exfoliated Large-Area Two-Dimensional MoS2 Nanolayers with Porphyrins for Improved Light Harvesting.

Molybdenum disulfide (MoS2 ) is a promising candidate for electronic and optoelectronic applications. However, its application in light harvesting has been limited in part due to crystal defects, often related to small crystallite sizes, which diminish charge separation and transfer. Here we demonstrate a surface-engineering strategy for 2D MoS2 to improve its photoelectrochemical properties. Chemically exfoliated large-area MoS2 thin films were interfaced with eight molecules from three porphyrin families: zinc(II)-, gallium(III)-, iron(III)-centered, and metal-free protoporphyrin IX (ZnPP, GaPP, FePP, H2 PP); metal-free and zinc(II) tetra-(N-methyl-4-pyridyl)porphyrin (H2 T4, ZnT4); and metal-free and zinc(II) tetraphenylporphyrin (H2 TPP, ZnTPP). We found that the photocurrents from MoS2 films under visible-light illumination are strongly dependent on the interfacial molecules and that the photocurrent enhancement is closely correlated with the highest occupied molecular orbital (HOMO) levels of the porphyrins, which suppress the recombination of electron-hole pairs in the photoexcited MoS2 films. A maximum tenfold increase was observed for MoS2 functionalized with ZnPP compared with pristine MoS2 films, whereas ZnT4-functionalized MoS2 demonstrated small increases in photocurrent. The application of bias voltage on MoS2 films can further promote photocurrent enhancements and control current directions. Our results suggest a facile route to render 2D MoS2 films useful for potential high-performance light-harvesting applications.

The impact of modifying the ligands on hydrogen production electro-catalyzed by meso-tetra-p-X-phenylporphin cobalt complexes, CoT(X)PP

Two molecular electro-catalysts based on cobalt complexes CoT(X)PP 1 (X=Cl) and 2 (X=OMe) are formed by the reaction of meso-tetra-p-X-phenylporphin, H2T(X)PP with cobalt compound for electrolytic proton or water reduction. 1 electrocatalyzes hydrogen evolution from acetic acid with a turnover frequency (TOF) of 85.51mol of hydrogen per mole of catalyst per hour at an overpotential (OP) of 941.6mV (in DMF), and from aqueous buffer solution (pH 7.0) with a TOF of 632.9mol of hydrogen per mole of catalyst per hour at an OP of 837.6mV. And 2 electrocatalyzes hydrogen evolution from acetic acid with a TOF of 48.70mol of hydrogen per mole of catalyst per hour at an OP of 941.6mV (in DMF), and from aqueous buffer solution (pH 7.0) with a TOF of 120.1mol of hydrogen per mole of catalyst per hour at an OP of 837.6mV. These results indicate that the electronic properties of the ligands play vital roles in determining the catalytic activities of the cobalt complexes, and are consistent with an evident increase in the catalytic activity when electron-withdrawing groups are present at phenylporphin, and meso-tetra-p-chloro-phenylporphin constitutes the better active catalyst.

Field-Induced Slow Magnetic Relaxation in a Mononuclear Manganese(III)-Porphyrin Complex.

We report on a novel manganese(III)-porphyrin complex with the formula [Mn(III) (TPP)(3,5-Me2 pyNO)2 ]ClO4 ⋅CH3 CN (2; 3,5-Me2 pyNO=3,5-dimethylpyridine N-oxide, H2 TPP=5,10,15,20-tetraphenylporphyrin), in which the Mn(III) ion is six-coordinate with two monodentate 3,5-Me2 pyNO molecules and a tetradentate TPP ligand to build a tetragonally elongated octahedral geometry. The environment in 2 is responsible for the large and negative axial zero-field splitting (D=-3.8 cm(-1) ), low rhombicity (E/|D|=0.04) of the high-spin Mn(III) ion, and, ultimately, for the observation of slow magnetic-relaxation effects (Ea =15.5 cm(-1) at H=1000 G) in this rare example of a manganese-based single-ion magnet (SIM). Structural, magnetic, and electronic characterizations were carried out by means of single-crystal diffraction studies, variable-temperature direct- and alternating-current measurements and high-frequency and -field EPR spectroscopic analysis followed by quantum-chemical calculations. Slow magnetic-relaxation effects were also observed in the already known analogous compound [Mn(III) (TPP)Cl] (1; Ea =10.5 cm(-1) at H=1000 G). The results obtained for 1 and 2 are compared and discussed herein.

Interaction of meso-tetraarylporphyrins with formic acid: A variable temperature 1H NMR study

Abstract The dications of meso-tetraphenylporphyrin, H2TPP, meso-tetra(4-Cl)phenylporphyrin, H2T(4-Cl)PP and meso-tetra(4-OCH3phenyl)porphyrin, H2T(4-OCH3)PP with formic acid as a weak carboxylic acid have been studied by UV–vis and variable temperature 1H NMR spectroscopies. As would be expected in the presence of a strongly basic counter anion, the formation of very strong N–H–O hydrogen bonds between the diprotonated species and the formate anion leads to considerable broadening of the NH resonance of H2T(4-OCH3)PP(HCOOH)2, H2T(4-Cl)PP(HCOOH)2 and H2TPP(HCOOH)2, so that the signal cannot be observed at or close to room temperatures, but appears at 0 °C for H2T(4-OCH3)PP(HCOOH)2 and at − 30 °C for the latter dications. While the signal of the β protons of H2TPP(HCOOH)2 moves continuously upfield from 20 to − 60 °C, the corresponding signal of H2T(4-OCH3)PP(HCOOH)2 and H2T(4-Cl)PP(HCOOH)2 moves upfield at higher temperatures and downfield at lower temperatures, corresponding to a decrease followed by an increase in the porphyrin ring current.

Thermodynamic study of complex formation process of free base meso-tetraphenylporphyrins with dimethyl and dibutyltin(IV) dichloride: a new algorithm for a single thermometric titration

A novel, fast and easy single sample measurement has been developed based upon temperature dependence of equilibrium constant in order to determine the enthalpy and entropy changes of a complexation reaction using spectrophotometric temperature titration. The method can be used in determination of the formation constant and thermodynamic parameters of the solutions that there are difficulties in their titration where volatile compounds are studying. Knowledge of component spectra is not required for the analysis. The formation constants of the interactions of s-di and tri-brominated meso-tetraphenylporphyrins, and meso-tetrakis(4-methylphenyl) and (4-methoxyphenyl) porphyrins with Me2SnCl2 and Bu2SnCl2, have been determined in range of 0–25 °C utilizing van’t Hoff relation, mass balance and equilibrium constant equations by an iterative least squares method with ΔH0 as adjustable parameter. The outputs of analysis are the equilibrium constants, ligand and adduct spectral profiles, their concentrations as a function of temperature, the adjusted values of the standard enthalpy ΔH0, and entropy ΔS0 changes. The order of formation constants of the resulting 1:1 complexes decreased with increasing number of bromide substituents and increased with adding methyl and methoxy groups, and vary as H2T(4-CH3O)PP > H2T(4-CH3)PP > H2TPP > H2TPPBr2 > H2TPPBr3 and Me2SnCl2 > Bu2SnCl2.

Charge-transfer complexes of meso-substituted porphines

Charge-transfer (CT) complexes of 5,10,15,20-tetramethyl-21H,23H-porphine [H2(tmp)] and 5,10,15,20-tetraphenyl-21H,23H-porphine [H2(tpp)] have been prepared with TCNQ-type (TCNQ = 7,7,8,8-tetracyanoquinodimethane) acceptors. The complexes crystallize in a mixed-stacked structure. The electronic state of the complexes has been investigated by combining structural geometry information of the acceptors with vibrational spectroscopy data. The complexes were found to possess neutral ground states. The difference between the donor oxidation potential and the acceptor reduction potential (ΔE) also supports this designation of their electronic states. The CT absorption energy shows a linear correlation with ΔE, which is expected for CT complexes in their neutral ground states. The frontier orbitals of the porphyrin donor that participate in the CT interactions have been examined by calculating the overlap integral between the donor occupied molecular orbitals and acceptor LUMO in the complexes. In the H2(tmp) and H2(tpp) complexes, a2u- and a1u-type porphyrin HOMO and next-HOMO, respectively, are suggested to both be contributors to the establishment of π–π* CT interactions and formation of the complex.

Intriguing Electrochemical Behavior of Free Base Porphyrins: Effect of Porphyrin–meso-Phenyl Interaction Controlled by Position of Substituents on meso-Phenyls

Electrochemical properties of substituted free base meso-tetraphenylporphyrins (H(2)T(o,o'-X)PP, H(2)T(o-X)PP, and H(2)T(p-X)PP, where X = OCH(3), CH(3), H, F, or Cl on the phenyl rings) are examined by cyclic voltammetry. When a substituent is located only at the para position of the meso-phenyl group, the difference between the first and second oxidation potentials (ΔE(ox), i.e., E(2)(ox) - E(1)(ox)), is generally significantly smaller than those of the H(2)TPPs with bulky o,o'-substituents on the phenyl group. This trend is elucidated with density functional theory calculations and attributed mainly to the sterically controlled π-conjugation of the meso-phenyl groups to the central porphyrin ring, rather than the often discussed deformation of porphyrin.

Synthesis and characterization of new molecular complexation between free base meso-tetraarylporphyrins and nitrosonium ion as π-acceptor

NOBF4 reacts with para-substituted meso-tetraarylporphyrins, H2t(4-Xp)p, at room temperature for formation of green molecular complexes, [H2t(4-Xp)p(NO)]BF4. Mole ratio for the porphyrins and nitrosonium ion in the molecular complexes was 1:1, [H2T(4-X)PP(NO)]BF4. FT-IR, UV–Vis, (1H and 13C) NMR spectral data, elemental analysis and molar conductivity indicated that NO+ (as electron acceptor) is bound to the lone electron pairs of the two pyrrolenine nitrogens in a side of the porphyrin plane. In these molecular complexes, two pyrrolic nitrogen atoms of the porphyrin core coordinate to the acceptor and two protons of the pyrrolic nitrogen atoms have been remained on the porphyrin macrocycles. Molecular complexation of meso-tetraarylporphyrins with NO+ produces a large downfield shift for the NH signal.

Synthesis, Nanostructure, Functionality, and Application of Polyfluorene-block-poly(N-isopropylacrylamide)s

A series of amphiphilic rod−coil diblock copolymers with a polyfluorene (PF) as a hydrophobic and light-emitting rod and a poly(N-isopropylacrylamide) (PNIPAAm) as a hydrophilic coil were prepared. Their micellar nanostructures and fluorescence properties were stimulated using solvents, e.g., water and tetrahydrofuran (THF)/toluene (1:10 by volume), which were characterized using dynamic light scattering (DLS), transmission electron microscopy (TEM), atomic force microscopy (AFM), and fluorescence spectroscopy. A typical block copolymer P2 (Mn = 14 400, Mw/Mn = 1.80, the PF weight fraction is 9.4%) in water exhibited micelles with the PNIPAAm block as the corona, whereas the polymer showed inverse micelles in mixed organic solvents of THF/toluene with PF as the corona. Such different nanostructures resulted in their different fluorescence properties. The fluorescence spectrum of P2 did not indicate aggregations of the PF chains in the THF/toluene mixture. Blue emission with a high quantum yield (0.80) was observed. In contrast, strong aggregations of the PF chains were observed in the aqueous solution, resulting in low quantum efficient (0.26) fluorescence. These results clearly demonstrated that the functionality of the P2 could be tuned through the solvent stimuli. The micelles of P2 were further used as nanocarriers to load a water-insoluble tetrakis(mesityl)porphyrin (H2(Me3)TPP) into its micellar aqueous solution. Efficient fluorescence resonance energy transfer (FRET) between the PF (donor) and H2(Me3)TPP (acceptor) (as high as 98% quenching of donor emission) was observed in their micellar solutions. Moreover, FRET contributes significantly to the efficiency of singlet oxygen generation from H2(Me3)TPP molecules (with an efficiency factor of 2 as compared to non-FRET micelles). This study provided a feasible way to enable the application of water-insoluble porphyrin in aqueous solution and enhance its singlet oxygen generation efficiency.

Spectrophotometric Studies of the Thermodynamics of Molecular Complexation between Free Base Meso-Tetraarylporphyrins and Iodine(III) Chloride

A spectrophotometric method was used for the molecular complexation of ICl3 with para-substituted meso-tetraarylporphyrins (H2t(4-X)pp; X: OCH3, CH(CH3)2, CH3, H and Cl) in methanol/chloroform (2.5% v/v) solution. The equilibrium constants and the thermodynamic parameters were measured spectrophotometrically at various temperatures for 1:1 molecular complex formation of meso-tetraarylporphyrins as electron donors with ICl3 as the electron acceptor. The formation constants for the molecular complexes change according to the following trend: [ICl3(H2t(4-OCH3)pp)]>[ICl3(H2t(4-CH(CH3)2)pp)]>[ICl3(H2t(4-CH3)pp)]>[ICl3(H2tpp)]>([ICl3(H2t(4-Cl)pp)]. Further, the thermodynamic parameters, ΔG o,ΔH o and ΔS o, for formation of the complexes were obtained.

Fluorescent porphyrins covalently bound to silica xerogel matrices

We study the influence of the nature and ring positioning of amino, hydroxy, and carboxy substituent groups on the fluorescence and some other physicochemical properties of free (H2TPP) and metalled tetraphenylporphyrins (MTPP). Furthermore, we have studied the feasibility of covalently bonding TPP species on the surface of the pores of a silica matrix prepared by the sol–gel method through the bridging action of either one of the following functionalized alkoxides: 3-isocyanatopropyltriethoxysilane, (IPTES) or 3-aminopropyltriethoxysilane (APTES). Importantly, the red fluorescence observed in free porphyrin solutions is preserved even after the macrocyclic species is covalently bound to the silica matrix. The formation of a chemical union between the porphyrin substituting groups and the organic groups of the IPTES or APTES alkoxides render the H2P-f precursory species has been proved successful by FTIR spectroscopy; likewise, the bond between Si-OH groups on the silica surface and the H2P-f has been made evident. The best results, in terms of fluorescence preservation, are obtained by using a TPP substituted with –NH2 groups in the ortho position of the phenyl rings, i.e. H2T(o-NH2)PP. A comparative fluorescence study of xerogels physically grafted or covalently bound with the latter TPP species confirm that, in the first case, the interaction of the molecule with the silanol groups of the silica surface of the gel inhibits fluorescence; while in the second case fluorescence is preserved.

Thermodynamic studies of sitting-atop (SAT) complexation of uranyl and free base meso -tetraarylporphyrins

The interaction of uranyl with meso-tetraphenylporphyrin and its para-substituted derivatives (H2t(4-X)pp, X : H, Br, Cl, CH(CH3)2, OCH3, CH3) in chloroform produced 1 : 1 sitting-atop (SAT) complexes ((uranyl)H2t(4-X)pp). Formation constants were calculated by computer fitting of complex absorbance versus mole ratio data to appropriate equations and found to decrease with temperature increase. Thermodynamic parameters, ΔG 0, ΔH 0 and ΔS 0 were obtained. The formation constants vary with changing of the substituent on the aryl rings of H2t(4-X)pp in the following order: (uranyl)H2t(4-OCH3)pp > (uranyl)H2t(4-CH3)pp > (uranyl)H2t(4-CH(CH3)2)pp > (uranyl)H2tpp > (uranyl)H2t(4-Br)pp > (uranyl)H2t(4-Cl)pp.