Showing papers on "Porphyrin published in 2004"
TL;DR: In this article, the effect of porphyrin substituent, functional group position, linker conjugation, binding group and electrolyte on the porphrin light harvesting efficiency was investigated.
756 citations
441 citations
TL;DR: In this paper, an overview of optical limiting properties of materials like porphyrins and phthalocyanines is given, with a special attention to the modulation of these materials aiming to achieve effective systems in terms of OL performance through the appropriate combination and modulation of several structural components.
406 citations
TL;DR: A derivatized porphyrin with long alkyl chains, 5,10,15,20-tetrakis(hexadecyloxyphenyl)-21H,23H-porphine, is selective toward semiconducting single-walled carbon nanotubes (SWNTs) in presumably noncovalent interactions, resulting in significantly enriched semiconductor SWNTs in the solubilized sample.
Abstract: A derivatized porphyrin with long alkyl chains, 5,10,15,20-tetrakis(hexadecyloxyphenyl)-21H,23H-porphine, is selective toward semiconducting single-walled carbon nanotubes (SWNTs) in presumably noncovalent interactions, resulting in significantly enriched semiconducting SWNTs in the solubilized sample and predominantly metallic SWNTs in the residual solid sample according to Raman, near-IR absorption, and bulk conductivity characterizations.
401 citations
TL;DR: The diameter of the nanotubes can be altered by modifying the structure of one of the porphyrin tectons, and are composed of J-aggregates that exhibit resonance light scattering.
Abstract: Porphyrin nanotubes are made by ionic self-assembly of two oppositely charged synthetic porphyrin molecules. The diameter of the nanotubes can be altered by modifying the structure of one of the porphyrin tectons. The nanotubes are photocatalytically active, mechanically responsive to light, and are composed of J-aggregates that exhibit resonance light scattering.
399 citations
TL;DR: A variety of directly linked porphyrin arrays including linear, windmill, gridlike, cyclic, and box architectures are developed, which exhibit an exceptionally low HOMO-LUMO gap as a result of a fully conjugated pi electronic system over a coplanar platform.
Abstract: On the basis of the Ag(I)-promoted coupling reaction of Zn(II) 5,15-diaryl porphyrin that gave a meso−meso-linked diporphyrin, we developed a variety of directly linked porphyrin arrays including linear, windmill, gridlike, cyclic, and box architectures. Electronic and excitonic interactions are thus fine tuned by placing porphyrin chromophores in well-defined arrangements. Photoexcited-state dynamics of these porphyrin arrays, as revealed by various ultrafast laser-based measurements, are pertinent to photosynthetic light-harvesting antenna in terms of very efficient excitation energy hopping over many porphyrins and lack of a defect that acts as energy sink. The conformational flexibility of a meso−meso-linked diporphyrin has also been used for the fine tuning of excitonic interactions as demonstrated by strapped meso−meso diporphyrins and reversible switching of energy transfer in a triporphyrin. Triply linked porphyrin arrays have also been explored, which exhibit an exceptionally low HOMO−LUMO gap as...
368 citations
TL;DR: The first example of a working model of the photosynthetic antenna-reaction center complex, constructed via self-assembled supramolecular methodology, is reported, and it is reported that the important feature of the present model system is its relative "simplicity".
Abstract: The first example of a working model of the photosynthetic antenna-reaction center complex, constructed via self-assembled supramolecular methodology, is reported. For this, a supramolecular triad is assembled by axially coordinating imidazole-appended fulleropyrrolidine to the zinc center of a covalently linked zinc porphyrin−boron dipyrrin dyad. Selective excitation of the boron dipyrrin moiety in the boron dipyrrin−zinc porphyrin dyad resulted in efficient energy transfer (kENTsinglet = 9.2 × 109 s-1; ΦENTsinglet = 0.83) creating singlet excited zinc porphyrin. Upon forming the supramolecular triad, the excited zinc porphyrin resulted in efficient electron transfer to the coordinated fullerenes, resulting in a charge-separated state (kcssinglet = 4.7 × 109 s-1; ΦCSsinglet = 0.9). The observed energy transfer followed by electron transfer in the present supramolecular triad mimics the events of natural photosynthesis. Here, the boron dipyrrin acts as antenna chlorophyll that absorbs light energy and tra...
299 citations
TL;DR: The two-photon absorption spectra of a series of conjugated porphyrin dimers are presented and it is demonstrated that they possess extremely large intrinsic peak 2PA cross sections, up to sigma2 = 1 x 104 GM in the near-IR region; these are among the highest values measured for any organic molecule.
Abstract: We present the two-photon absorption (2PA) spectra of a series of conjugated porphyrin dimers and show that they possess extremely large intrinsic (femtosecond) peak 2PA cross sections, up to sigma2 = 1 x 104 GM in the near-IR region; these are among the highest values measured for any organic molecule. Moreover, we demonstrate that the second-order perturbation theory applied to a simple three-level model gives a perfect quantitative description of the observed 2PA cross section. By comparing all the factors of the three-level model for dimers with those of corresponding monomer (for which sigma2 = 20 GM), we explain an approximately 500-fold cooperative enhancement in sigma2 and find that the most important factor is the strength of excited-state transition. The matrix element of dipole moment of this transition amounts gigantic values of 30-40 D for conjugated porphyrin dimers, which can be accounted for a large delocalization radius (large electron-hole separation) in this state. We also demonstrate efficient generation of singlet oxygen upon one- and two-photon excitation of these porphyrin dimers, which can be useful for two-photon initiated photodynamic therapy of cancer.
255 citations
TL;DR: A family of red light-emitting star-shaped porphyrins with four monodisperse conjugated oligofluorene arms was prepared by using two key reactions: Lindsey condensation and Suzuki-Miyaura cross coupling reactions.
Abstract: A family of red light-emitting star-shaped porphyrins with four monodisperse conjugated oligofluorene arms was prepared by using two key reactions: Lindsey condensation and Suzuki−Miyaura cross coupling reactions. All porphyrins exhibit high quantum yields (about 0.22) and good solubility in common organic solvents, and form high-quality solid films. Optical studies showed that the star-shaped oligomers could absorb blue light and emit saturated red light via efficient energy transfer from the fluorene segments to the porphyrin core.
221 citations
TL;DR: Steady-state fluorescence measurements demonstrated that the donor chromophores transfer excited-state energy to the porphyrin with 97% efficiency, and enhanced singlet oxygen luminescence was observed from oxygen-saturated solutions of the target compound under two-photon excitation conditions.
Abstract: A new approach to two-photon excited photodynamic therapy has been developed. A dendritic array of eight donor chromophores capable of two-photon absorption (TPA) was covalently attached to a central porphyrin acceptor. Steady-state fluorescence measurements demonstrated that the donor chromophores transfer excited-state energy to the porphyrin with 97% efficiency. Two-photon excitation of the donor chromophores at 780 nm resulted in a dramatic increase in porphyrin fluorescence relative to a porphyrin model compound. Enhanced singlet oxygen luminescence was observed from oxygen-saturated solutions of the target compound under two-photon excitation conditions.
219 citations
TL;DR: The final charge-separated state decays, obeying first-order kinetics, with a long lifetime that is comparable with that of the natural bacterial photosynthetic reaction center and the quantum yield remains high, despite the large separation distance between the Fc+ and C60*- moieties.
Abstract: A meso,meso-linked porphyrin trimer, (ZnP) 3 , as a light-harvesting chromophore, has been incorporated for the first time into a photosynthetic multistep electron-transfer model including ferrocene (Fc) as an electron donor and fullerene (C 6 0 ) as an electron acceptor, to construct the ferrocene-meso,meso-linked porphyrin trimer-fullerene system Fc-(ZnP) 3 -C 6 0 . Photoirradiation of Fc-(ZnP) 3 -C 6 0 results in photoinduced electron transfer from both the singlet and triplet excited states of the porphyrin trimer, 1 (ZnP)* 3 and 3 (ZnP)* 3 , to the C 6 0 moiety to produce the porphyrin trimer radical cation-C 6 0 radical anion pair, Fc-(ZnP) 3 . + -C 6 0 . - . Subsequent formation of the final charge-separated state Fc + -(ZnP) 3 -C 6 0 . - was confirmed by the transient absorption spectra observed by pico- and nanosecond time-resolved laser flash photolysis. The final charge-separated state decays, obeying first-order kinetics, with a long lifetime (0.53 s in DMF at 163 K) that is comparable with that of the natural bacterial photosynthetic reaction center. More importantly, the quantum yield of formation of the final charge-separated state (0.83 in benzonitrile) remains high, despite the large separation distance between the Fc + and C 6 0 . - moieties. Such a high quantum yield results from efficient charge separation through the porphyrin trimer, whereas a slow charge recombination is associated with the localized porphyrin radical cation in the porphyrin trimer. The light-harvesting efficiency in the visible region has also been much improved in Fc-(ZnP) 3 -C 6 0 because of exciton coupling in the porphyrin trimer as well as an increase in the number of porphyrins.
TL;DR: The efficient catalysis by Co(2)(DPX) for the four-electron reduction of dioxygen by Fe(C(5)H(4)Me)(2) results from the strong binding of the reduced oxygen with Co( 2)( DPX) which has a subtle distance between two cobalt nuclei for the oxygen binding.
Abstract: The selective two-electron reduction of dioxygen occurs in the case of a monocobalt porphyrin [Co(OEP)], whereas the selective four-electron reduction of dioxygen occurs in the case of a cofacial dicobalt porphyrin [Co2(DPX)]. The other cofacial dicobalt porphyrins [Co2(DPA), Co2(DPB), and Co2(DPD)] also catalyze the two-electron reduction of dioxygen, but the four-electron reduction is not as efficient as in the case of Co2(DPX). The μ-superoxo species of cofacial dicobalt porphyrins were produced by the reactions of cofacial dicobalt(II) porphyrins with dioxygen in the presence of a bulky base and the subsequent one-electron oxidation of the resulting μ-peroxo species by iodine. The superhyperfine structure due to two equivalent cobalt nuclei was observed at room temperature in the ESR spectra of the μ-superoxo species. The superhyperfine coupling constant of the μ-superoxo species of Co2(DPX) is the largest among those of cofacial dicobalt porphyrins. This indicates that the efficient catalysis by Co2(...
TL;DR: It is concluded that charge separation in these hybrid systems occurs through space in unsymmetrical conformations, where the center-to-center distance between the component pi-systems is minimized.
Abstract: As part of a continuing investigation of the topological control of intramolecular electron transfer (ET) in donor-acceptor systems, a symmetrical parachute-shaped octaethylporphyrin-fullerene dyad has been synthesized. A symmetrical strap, attached to ortho positions of phenyl groups at opposing meso positions of the porphyrin, was linked to [60]-fullerene in the final step of the synthesis. The dyad structures were confirmed by H-1, C-13, and He-3 NMR, and MALDI-TOF mass spectra. The free-base and Zn-containing dyads were subjected to extensive spectroscopic, electrochemical and photophysical studies. UV-vis spectra of the dyads are superimposable on the sum of the spectra of appropriate model systems, indicating that there is no significant ground-state electronic interaction between the component chromophores. Molecular modeling studies reveal that the lowest energy conformation of the dyad is not the C-2v symmetrical structure, but rather one in which the porphyrin moves over to the side of the fullerene sphere, bringing the two pi-systems into close proximity, which enhances van der Waals attractive forces. To account for the NMR data, it is proposed that the dyad is conformationally mobile at room temperature, with the porphyrin swinging back and forth from one side of the fullerene to the other. The extensive fluorescence quenching in both the free base and Zn dyads is associated with an extremely rapid photoinduced electron-transfer process, k(ET) approximate to 10(11) s(-1), generating porphyrin radical cations and C-60 radical anions, detected by transient absorption spectroscopy. Back electron transfer (BET) is slower than charge separation by up to 2 orders of magnitude in these systems. The BET rate is slower in nonpolar than in polar solvents, indicating that BET occurs in the Marcus inverted region, where the rate decreases as the thermodynamic driving force for BET increases. Transient absorption and singlet molecular oxygen sensitization data show that fullerene triplets are formed only with the free base dyad in toluene, where triplet formation from the charge-separated state is competitive with decay to the ground state. The photophysical properties of the P-C-60 dyads with parachute topology are very similar to those of structurally related rigid pi-stacked P-C-60 dyads, with the exception that there is no detectable charge-transfer absorption in the parachute systems, attributed to their conformational flexibility. It is concluded that charge separation in these hybrid systems occurs through space in unsymmetrical conformations, where the center-to-center distance between the component pi-systems is minimized. Analysis of the BET data using Marcus theory gives reorganization energies for these systems between 0.6 and 0.8 eV and electronic coupling matrix elements between 4.8 and 5.6 cm(-1).
TL;DR: In this article, an improved methodology was reported for the regioselective nitration of the phenyl groups of meso-tetraphenylporphyrin 1, using NaNO2 and TFA.
TL;DR: Overall, the self-assembled porphyrin boxes Bn serve as a well-defined three-dimensional model for the light-harvesting complex.
Abstract: meso-Pyridine-appended zinc(II) porphyrins Mn and their meso−meso-linked dimers Dn assemble spontaneously, in noncoordinating solvents such as CHCl3, into tetrameric porphyrin squares Sn and porphyrin boxes Bn, respectively. Interestingly, formation of Bn from Dn proceeds via homochiral self-sorting assembly, which has been verified by optical separations of B1 and B2. Optically pure enantiomers of B1 and B2 display strong Cotton effects in the CD spectra, which reflect the length of the pyridyl arm, thus providing evidence for the exciton coupling between the noncovalent neighboring porphyrin rings. Excitation energy migration processes within Bn have been investigated by steady-state and time-resolved spectroscopic methods in conjunction with polarization anisotropy measurements. Both the pump-power dependence on the femtosecond transient absorption and the transient absorption anisotropy decay profiles are directly associated with the excitation energy migration process within the Bn boxes, where the e...
TL;DR: Encapsulated transition metal catalysts are presented that are formed by templated self-assembly processes of simple building blocks such as porphyrins and pyridylphosphine and phosphite ligands, using selective metal-ligand interactions, leading to a new class of transition metals catalysts.
Abstract: Encapsulated transition metal catalysts are presented that are formed by templated self-assembly processes of simple building blocks such as porphyrins and pyridylphosphine and phosphite ligands, using selective metal−ligand interactions. These ligand assemblies coordinate to transition metals, leading to a new class of transition metal catalysts. The assembled catalyst systems were characterized using NMR and UV−vis spectroscopy and were identified under catalytic conditions using high-pressure infrared spectroscopy. Tris-3-pyridylphosphine binds three mesophenyl zinc(II) porphyrin units and consequently forms an assembly with the phosphorus donor atom completely encapsulated. The encapsulated phosphines lead exclusively to monoligated transition metal complexes, and in the rhodium-catalyzed hydroformylation of 1-octene the encapsulation of the catalysts resulted in a 10-fold increase in activity. In addition, the branched aldehyde was formed preferentially (l/b = 0.6), a selectivity that is highly unusu...
TL;DR: In this article, a review of coordination chemistry and structures of mainly Sn(IV) porphyrins is presented, although the rarer Sn(II) complexes are also described.
TL;DR: In this article, a composite molecular nanoclusters of dendritic porphyrin and fullerene were used for organic photovoltaic cells, which absorb light over entire spectrum of visible light.
Abstract: Novel organic solar cells have been prepared using molecular clusters of porphyrin dendrimer (donor) and fullerene (acceptor) dye units assembled on SnO2 electrodes. The molecular clusters of porphyrin with dendritic structure and fullerene exhibit controlled size and shape in contrast with the reference systems (a porphyrin dimer and a porphyrin−fullerene dyad) without dendritic structure in TEM images, which show rather irregular and smaller clusters. The composite molecular nanoclusters of dendritic porphyrin and fullerene prepared in acetonitrile/toluene mixed solvent absorb light over entire spectrum of visible light. The comparison of photoelectrochemical properties of composite molecular cluster of porphyrin and fullerene with that of molecular cluster of porphyrin−C60 dyad with covalent linkage shows the importance of interpenetrating structure in each network to transport hole and electron efficiently. Furthermore, organic photovoltaic cells using clusters of supramolecular complexes of V-shaped ...
TL;DR: Higher fullerenes (>/=C76) were selectively extracted from a fullerene mixture obtained from a combustion-based industrial production source by cyclic dimers of beta-unsubstituted porphyrin zinc complexes 2C5-2C7 with C5-C7 alkylene spacers as host molecules.
Abstract: Higher fullerenes (≥C76) were selectively extracted from a fullerene mixture obtained from a combustion-based industrial production source by cyclic dimers of β-unsubstituted porphyrin zinc complexes 2C5−2C7 with C5−C7 alkylene spacers as host molecules. Results of single extraction of the fullerene mixture with 2C5−2C7 together with a β-substituted analogue of 2C6 (1C6) and spectroscopic titration of 2C6 and 1C6 with C60, C70, and C96 indicated that the host selectivity toward higher fullerenes is much dependent on the structure of the porphyrin units and the size of the host cavity. Sequential three-stage extraction of the fullerene mixture with the best-behaved 2C6 resulted in considerable enrichment in very rare fullerenes C102−C110 (<0.1 abs %) up to 82 abs % (C76−C114, 99 abs %) (356 nm) of total fullerenes.
TL;DR: Novel PSs described in the present study, belonging both to the porphyrin and chlorin series, have proven more effective than Photofrin in killing colon cancer cells in vitro; extending these observation to in vivo models might lead to significant advances in the development of tumor PDT.
TL;DR: In this article, three new Mn(III) porphyrin catalysts of O2− dismutation (superoxide dismutase mimics), bearing ether oxygen atoms within their side chains, were synthesized and characterized.
Abstract: Three new Mn(III) porphyrin catalysts of O2˙− dismutation (superoxide dismutase mimics), bearing ether oxygen atoms within their side chains, were synthesized and characterized: Mn(III) 5,10,15,20-tetrakis[N-(2-methoxyethyl)pyridinium-2-yl]porphyrin (MnTMOE-2-PyP5+), Mn(III)5,10,15,20-tetrakis[N-methyl-N′-(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTM,MOE-2-ImP5+) and Mn(III) 5,10,15,20-tetrakis[N,N′-di(2-methoxyethyl)imidazolium-2-yl]porphyrin (MnTDMOE-2-ImP5+). Their catalytic rate constants for O2˙− dismutation( disproportionation) and the related metal-centered redox potentials vs. NHE are: log kcat
= 8.04 (E1/2
=
+251 mV) for MnTMOE-2-PyP5+, log kcat
= 7.98 (E1/2
=
+356 mV) for MnTM,MOE-2-ImP5+ and log kcat
= 7.59 (E1/2
=
+365 mV) for MnTDMOE-2-ImP5+. The new porphyrins were compared to the previously described SOD mimics Mn(III) 5,10,15,20-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP5+), Mn(III) 5,10,15,20-tetrakis(N-n-butylpyridinium-2-yl)porphyrin (MnTnBu-2-PyP5+) and Mn(III) 5,10,15,20-tetrakis(N,N′-diethylimidazolium-2-yl)porphyrin (MnTDE-2-ImP5+). MnTMOE-2-PyP5+ has side chains of the same length and the same E1/2, as MnTnBu-2-PyP5+
(kcat
= 7.25, E1/2
=
+ 254 mV), yet it is 6-fold more potent a catalyst of O2˙− dismutation, presumably due to the presence of the ether oxygen. The log kcatvs. E1/2 relationship for all Mn porphyrin-based SOD mimics thus far studied is discussed. None of the new compounds were toxic to Escherichia coli in the concentration range studied (up to 30 μM), and protected SOD-deficient E. coli in a concentration-dependent manner. At 3 μM levels, the MnTDMOE-2-ImP5+, bearing an oxygen atom within each of the eight side chains, was the most effective and offered much higher protection than MnTE-2-PyP5+, while MnTDE-2-ImP5+ was of very low efficacy.
TL;DR: A series of Sauvage-type rotaxanes containing fullerene and tetraarylporphyrin moieties has been synthesized by a convergent route, yielding long-lived change-separated states in agreement with the large distance between the fulleren and porphyrin chromophores.
Abstract: A series of Sauvage-type rotaxanes containing [60]fullerene and tetraarylporphyrin moieties has been synthesized by a convergent route. Photoinduced energy-transfer and electron-transfer reactions in these rotaxanes yield long-lived change-separated states, in agreement with the large distance between the fullerene and porphyrin chromophores.
TL;DR: A dodecameric porphyrin wheel was prepared by Ag(I)-promoted intramolecular coupling of a linear p Morphyrin dodecamers and efficient energy hopping was revealed by femtosecond transient anisotropy measurements.
Abstract: A dodecameric porphyrin wheel was prepared by Ag(I)-promoted intramolecular coupling of a linear porphyrin dodecamer and was observed by scanning tunneling microscopy (STM). Efficient energy hopping along the array was revealed by femtosecond transient anisotropy measurements.
TL;DR: The electrochemical studies of the SAMs indicate that the tripodal tether provides a more robust anchor to the Au surface than does a tether with a single site of attachment, and the electron-transfer and charge-dissipation characteristics of the two tethers are generally similar.
Abstract: To examine the effects of molecular structure on charge storage in self-assembled monolayers (SAMs), a family of redox-active molecules has been prepared wherein each molecule bears a tether composed of a tripodal linker with three protected thiol groups for surface attachment. The redox-active molecules include ferrocene, zinc porphyrin, ferrocene-zinc porphyrin, magnesium phthalocyanine, and triple-decker lanthanide sandwich coordination compounds. The tripodal tether is based on a tris[4-(S-acetylthiomethyl)phenyl]-derivatized methane. Each redox-active unit is linked to the methane vertex by a 4,4'-diphenylethyne unit. The electrochemical characteristics of each compound were examined in solution and in SAMs on Au. Redox-kinetic measurements were also performed on the SAMs (with the exception of the magnesium phthalocyanine) to probe (1) the rate of electron transfer in the presence of an applied potential and (2) the rate of charge dissipation after the applied potential is disconnected. The electrochemical studies of the SAMs indicate that the tripodal tether provides a more robust anchor to the Au surface than does a tether with a single site of attachment. However, the electron-transfer and charge-dissipation characteristics of the two tethers are generally similar. These results suggest that the tripodal tether offers superior stability characteristics without sacrificing electrochemical performance.
TL;DR: In this Commentary, reactive intermediates that have been shown or proposed to be involved in iron porphyrin complex-catalyzed oxidation reactions are reviewed and the current controversy on the oxoiron(IV) poiryrin π-cation radical as a sole reactive species versus the involvement of multiple oxidizing species in oxygen transfer reactions is discussed.
Abstract: Oxoiron(IV) porphyrin π-cation radicals have been considered as the sole reactive species in the catalytic oxidation of organic substrates by cytochromes P450 and their iron porphyrin models over the past two decades. Recent studies from several laboratories, however, have provided experimental evidence that multiple oxidizing species are involved in the oxygen transfer reactions and that the mechanism of oxygen transfer is much more complex than initially believed. In this Commentary, reactive intermediates that have been shown or proposed to be involved in iron porphyrin complex-catalyzed oxidation reactions are reviewed. Particularly, the current controversy on the oxoiron(IV) porphyrin π-cation radical as a sole reactive species versus the involvement of multiple oxidizing species in oxygen transfer reactions is discussed.
TL;DR: In this paper, strong cooperative enhancement of simultaneous two-photon absorption cross section in a porphyrin dimer was reported, which corresponds to a 400-fold increase over the value measured for the monomer, and is one of the largest ever obtained for organic chromophore of similar size.
Abstract: We report strong cooperative enhancement of simultaneous two-photon absorption cross section in a porphyrin dimer. The two-photon cross section, σ2=6×10−47 cm4s/photon, corresponds to a 400-fold increase over the value measured for the monomer, and is one of the largest ever obtained for organic chromophore of similar size.
TL;DR: The behavior of amphiphilic porphyrins in biomimetic microenvironments provides evidences about the promissory activity of these agents in photodynamic therapy (PDT) and appears to be mainly responsible for the enzyme inactivation in these media.
Abstract: The photodynamic effect of 5-(4-carboxyphenyl)-10,15,20-tris(4-methylphenyl) porphyrin (H2P) and its metal complex with Zn(II), Pd(II), Cu(II) and Ni(II) has been compared in homogeneous medium and in reverse micelles of n-heptane/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/water bearing urease as biological substrate model. The formation of porphyrin metal complex produces changes mainly in the free-base porphyrin characteristic absorption Q-bands and in the fluorescence quantum yields (φF). The singlet molecular oxygen, O 2 ( 1 Δ g ) , production was evaluated using 9,10-dimethylanthracene (DMA) in tetrahydrofuran (THF) yielding values of ΦΔ ∼0.48, 0.77 and 0.88 for H2P, ZnP and PdP, respectively. DMA decomposition was not observed using CuP and NiP as sensitizer. The addition of β-carotene (Car) suppresses the O 2 ( 1 Δ g ) -mediated photooxidation of DMA. The photodynamic effect of these porphyrins on the urease activity was evaluated in water and in AOT reverse micelles. In both media, the enzyme photoinactivation increases with the sensitizer O 2 ( 1 Δ g ) production. Also, the addition of azide ion photoprotects the urease activity. Therefore, the O 2 ( 1 Δ g ) mediation appears to be mainly responsible for the enzyme inactivation in these media. The behavior of amphiphilic porphyrins in biomimetic microenvironments provides evidences about the promissory activity of these agents in photodynamic therapy (PDT).
TL;DR: Photonic control of photoinduced electron transfer has been demonstrated in a dimethyldihydropyrene (DHP) porphyrin (P) fullerene (C(60) molecular triad and may be useful for the design of molecule-based optoelectronic systems.
Abstract: Photonic control of photoinduced electron transfer has been demonstrated in a dimethyldihydropyrene (DHP) porphyrin (P) fullerene (C60) molecular triad. In the DHP−P−C60 form of the triad, excitation of the porphyrin moiety is followed by photoinduced electron transfer to give a DHP−P•+−C60•- charge-separated state, which evolves by a charge shift reaction to DHP•+−P−C60•-. This final state has a lifetime of 2 μs and is formed in an overall yield of 94%. Visible (≥300 nm) irradiation of the triad leads to photoisomerization of the DHP moiety to the cyclophanediene (CPD). Excitation of the porphyrin moiety of CPD−P−C60 produces a short-lived (<10 ns) CPD−P•+−C60•- state, but charge shift to the CPD moiety does not occur, due to the relatively high oxidation potential of the CPD group. Long-lived charge separation is not observed. Irradiation of CPD−P−C60 with UV (254 nm) light converts the triad back to the DHP form. Thermal interconversion of the DHP and CPD forms is very slow, photochemical cycling is fa...