Aggregation behavior of tetrakis(4-sulfonatophenyl)porphyrin in AOT/water/decane microemulsions

AOT/water/decane microemulsions have been used to entrap the water-soluble 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4). Quasi-elastic light scattering technique has confirmed the confinement of the porphyrin and its various aggregates into the inner water pool. Various species have been detected as function of the size of the microemulsions, concentration of the porphyrin, pH, and aging of the solutions by using a combination of UV-vis absorption, steady fluorescence emission, fluorescence lifetime measurements, and time-resolved fluorescence anisotropy. Under neutral pH conditions, the porphyrin is present as the free base monomer (S414) in the inner water compartment, and it is free to rotate when the size of the droplet is large enough and the porphyrin concentration is low. On increasing the concentration and/or decreasing the microemulsion size, a H-dimer of the free base (S406) is prevalently formed. Aging both the S414 and S406 species leads to the formation of a new species (S424), which has been postulated as a H-type dimer of the diacid porphyrin. On decreasing the pH, the species S414 and S406 almost instantaneously convert into the diacid porphyrin, which is monomeric (S434). This latter is an intermediate in the eventual formation of J-aggregated TPPS4 (S490). A marked stability has been observed for the S424 species, which do not interconvert on changing the pH of the bulk aqueous phase.     

In vitro EVALUATION OF PHOTOTOXIC PROPERTIES OF FOUR STRUCTURALLY RELATED BENZOPORPHYRIN DERIVATIVES

Four structural analogs of benzoporphyrin derivative (BPD) have been studied and compared for photosensitizing activity in vitro. All analogs have an identical reduced tetrapyrrol porphyrin ring, and differ by the position of a cyclohexadiene ring (fused at either ring A or ring B of the porphyrin) and the presence of either two acid groups or one acid and one ester group at rings C and D of the porphyrin. Photosensitizer activity was tested with the M1 tumor cell line using an assay (the MTT assay) which detects mitochondrial hydrogenases as a measure of cell viability. This assay was shown to be equivalent to the standard clonogenicity or [3H]thymidine uptake assay. Comparative studies with the BPD analogs showed that the monoacid derivatives had equivalent cytotoxicity and were about five-fold more active than the diacid forms. This was the case whether the assays were performed in the presence or absence of fetal calf serum.     

Study on nonlinear spectroscopy of tetraphenylporphyrin and dithiaporphyrin diacids

The nonlinear absorption of two porphyrin diacids (H4TPP2+ and H2DSP2+), the diprotonated forms of free base tetraphenylporphyrin (H2TPP) and dithiaporphyrin (DSP), were studied in the wavelength range of 500-650 nm. The two porphyrin diacids exhibited perturbed static and dynamic characteristics and enhanced nonlinear absorption properties relative to their parent neutral complexes in solution. Furthermore, for the dithiaporphyrin diacid, the introduction of S-atoms into the porphyrin core makes it a better candidate for optical limiting relative to the simple porphyrin. Their photophysical parameters such as ground and excited states absorption cross-sections, together with fluorescence lifetime and intersystem crossing time, were determined.     

Unusual Stepwise Protonation and J‐Aggregation of meso‐Tetrakis(N‐methylpyridinium‐4‐yl)porphine on Binding Poly(sodium vinylsulfonate)

The binding of a tetracationic porphyrin to a highly charged polymer like poly(sodium vinylsulfonate) has been investigated over a wide pH range and under various experimental conditions. We present evidence that, depending on the pH, the high electrostatic field exerted by the polymer stabilizes the diprotonated form of the free base porphyrin at unusual pH values or otherwise causes the formation of H‐type aggregates. In particular, at a low polymer concentration, lowering the pH at first allows the formation of the diacid species then it determines its reorganization in close‐packed J‐type aggregates. The employment of various metallo‐derivatives of the title porphyrin enables a better insight into the nature of all the detected species.     

双卟啉化合物的构象平衡及π-π作用研究

制备并表征了一系列以柔韧烷氧化相连的自由双卟啉及其锌配合物,以＾１Ｈ－ＮＭＲ考察了烷氧链长度及锌离子对双卟啉构象平衡的影响。结果表明,双卟啉存在开放式及闭合式构象平衡,随烷氧链的增长,构象平衡由开放式向闭合式移动,当链上碳原子数为４时最有利于双卟啉形成闭合式构象。     

Density functional theory studies on the Raman and IR spectra of meso-tetraphenylporphyrin diacid

The vibrational spectra of meso-tetraphenylporphyrin diacid (H4TPP2+) have been studied with the density functional theory. Raman and IR spectra of H4TPP2+ and its N-deuterated analogue (D4TPP2+) are measured and compared with the computational results. Complete assignments of observed IR and Raman bands were proposed on the bases of calculation results. The DFT calculations reproduce 140 observed fundamentals with the RMS 8.6 cm-1. The computational as well as the experimental results reveal that the saddle-distortion of porphyrin macrocycle for the diacid leads to a significant effect on its vibrational spectra. Especially, several out-of-plane skeletal modes, which were either unobserved or very weak in the Raman spectra of CuTPP and H2TPP, are activated in the Raman spectra of the diacids. In addition, enhancement for the Raman bands of phenyl CC stretching modes were observed and attributed to the conjugation effect of pi-systems of the phenyl and the porphyrinato macrocycles.     

四-(对-磺基苯基)卟啉二酸(H_4~(2+)TSPP)分子聚集体的共振喇曼光谱研究

研究了四－（对－磺基苯基）卟啉二酸（Ｈ２＋４ＴＳＰＰ）的Ｊ－聚集体共振喇曼光谱,用氘代法考察了各喇曼谱带的同位素位移．指认３条低波数喇曼带为分子聚集体的晶格模．喇曼光谱退偏比测量表明,聚集体中Ｈ２＋４ＴＳＰＰ的对称性较分子态降低．比较游离碱Ｈ２ＴＳＰＰ和分子态Ｈ２＋４ＴＳＰＰ共振喇曼光谱讨论了聚集体中Ｈ２＋４ＴＳＰＰ的结构变化．Ｈ２＋４ＴＳＰＰ在聚集体中以接近面对面方式排列     

Anion chelation-induced porphyrin protonation and its application for chloride anion sensing

The protonation of a simple meso-tetraphenylporphyrin in an organic-aqueous system was found to be induced by the counteranions. During the process of protonation, the counteranion of the proton sources binds with the porphyrin core and thus promotes the complexation of the porphyrin and protons. The interaction of porphyrin and anion was characterized by fluorescence, UV-visible, cyclic voltammetry, (1)H NMR, and IR. Moreover, it could be exploited in selective fluorescent sensing of Cl(-). The sensing mechanism was based on extraction of protons from the aqueous phase into the organic phase by free base porphyrin and simultaneous coextraction of Cl(-), which promoted porphyrin protonation, and hence resulted in significant changes of the porphyrin fluorescence spectra. Selectivity trends turned out to be dependent upon the lipophilicity of anion and the binding affinity and structure complementarity between the protonated porphyrin and anions. The fluorescence enhancement of the porphyrin band at 684 nm showed modest selectivity for Cl(-) and NO(3)(-).     

Synthesis, characterization and spectral properties of substituted tetraphenylporphyrin iron chloride complexes

A series of substituted tetraphenylporphyrin iron chloride complexes [RTPPFe(III)Cl, R=o/p-NO?, o/p-Cl, H, o/p-CH?, o/p-OCH?] were synthesized by a novel universal mixed-solvent method and the spectral properties of free base porphyrins and iron porphyrin compounds were compared with each other. The experimental results showed that the one-pot mixed solvent method was superior to the two-step method in the yields, reaction time and workup of reaction mixtures for the synthesis of iron porphyrin compounds. The highest yields (28.7%-40.4%) of RTPPFe(III)Cl were obtained in the mixed solvents propionic acid, glacial acetic acid and m-nitrotoluene under reflux for 2 h. A detailed analysis of ultraviolet-visible (UV-vis), infrared (IR) and far-infrared (FIR) spectra suggested the transformation from free base porphyrins to iron porphyrins. The red shift of the Soret band in ultraviolet-visible spectra due to the presence of p-nitrophenyl substituents and the blue shift of Fe-Cl bond of TPPFeCl in far-infrared spectra were further explained by the electron transfer and molecular planarity in the porphyrin ring.     

Large third-order optical nonlinearity of self-assembled porphyrin oligomers.

Third-order nonlinear optical properties of two series of self-assembled porphyrin wires, one being terminated by zinc porphyrin and the other by free base porphyrin, were measured by femtosecond time-resolved optical Kerr effect. The hyperpolarizability values of the latter series were extremely large ranging from 10-30 to 10-29 esu, 10 times larger than the former. The behavior is accounted for by the contribution of terminal free base porphyrin to enhance the molecular polarization by acceptor nature toward central metalloporphyrin array.     

Synthesis of Linear Amphipathic Porphyrin Dimers and Trimers: An Approach to Bilayer Lipid Membrane Spanning Porphyrin Arrays

A modular building-block approach has been developed for the construction of linear amphipathic porphyrin arrays. The reaction of meso-(trifluoromethyl)dipyrromethane and an aldehyde under the conditions of the two-step room temperature porphyrin synthesis affords the trans-substituted porphyrin (13-56% yields). A similar reaction with two different aldehydes provides access to porphyrins bearing two different functional groups. An ethyne porphyrin and an iodo porphyrin (either free base or zinc) are selectively joined via Pd(0)-catalyzed coupling reactions, affording a linear array with porphyrins in defined metalation states. Coupling of a zinc-porphyrin bearing iodo and ester groups with a free base porphyrin bearing ethyne and ester groups yielded the zinc-free base porphyrin dimer. Coupling of a bis-ethyne porphyrin with a porphyrin bearing iodo and ester groups afforded the porphyrin trimer. Cleavage of the esters yielded the amphipathic porphyrin dimer and trimer arrays. The arrays with adjacent zinc and free base porphyrins undergo efficient electronic energy transfer. Both amphipathic porphyrin arrays have been incorporated into L-alpha-phosphatidylcholine vesicles. This versatile synthetic strategy provides access to a family of porphyrin arrays for studies of photophysical processes in supramolecular assemblies.     

Precise synthesis of porphyrin array scaffolding polyisocyanides

Aryl isocyanides bearing free‐base and metallo‐porphyrins were prepared and polymerized with a Pd–Pt μ‐ethynediyl complex as the initiator to give polymers with narrow polydispersity indices. The molecular weights of the resulting polymers were precisely controlled by the initial feed ratio of the porphyrin monomer to the initiator. The UV–VIS spectra suggested that the porphyrin pendants are regularly arranged to form stacked columns. Metallo‐porphyrin polymers were also prepared by reacting free‐base porphyrin polymers with metal salts. The successive reactions of free‐base and zinc‐porphyrin monomers resulted in the formation of diblock polymers. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 585–595, 2006     

Separation of porphyrin-based photosensitizer isomers by laser-induced fluorescence capillary electrophoresis

Methods for the separation of photosensitizer isomers, such as benzoporphyrin derivative monoacid, benzoporphyrin ethyl monoacid, 2-[1-hexyloxyethyl]-2-devinylpyropheophorbide-a, diethyleneglycol diester benzoporphyrin derivative, tin ethyl etiopurpurin, and phthalocyanine tetrasulfonate, have been systematically developed by CE. Detection was accomplished by UV absorption at 214 nm or by LIF with excitation at 442/488 nm and emission at 690 nm. The effects of three major experimental parameters of buffer types, organic solvents, and surfactant additives are described. The optimized separation conditions were determined so as to provide satisfactory separation efficiency and analysis time. The methods are shown to be suitable for the separation and determination of porphyrin and phthalocyanines regioisomers, diastereoisomers, and enantiomers.     

Fluorescence Properties of Porphyrin Dimers Incorporating an Anhydride Linker

IntroductionOligomeric porphyrins play a number of criticalbiological roles in many processes, such as energytransfer and electron transfer, molecular binding, mul-tielectron redox catalysis and light harvest[1,2]. Amongthe arrays of covalently linked por…     

Photophysical investigation of neutral and diprotonated free-base bis(arylethynyl)porphyrins

The photophysical properties for a series of free-base arylethynyl porphyrins and the corresponding trans-disubstituted tetraphenylporphyrin (H(2)TPP) derivatives lacking arylethynyl functionalities have been studied via electronic absorption and emission spectroscopy in both neutral and diacid forms. Enhanced substituent effects on porphyrin absorption spectra are observed in the arylethynyl porphyrins relative to the H(2)TPP derivatives, owing to the presence of the ethynyl spacer that allows for a coplanar geometry between the porphyrin macrocycle and the appended phenyl substituents. Upon protonation, both series of porphyrins exhibit substantially red shifted absorption and emission spectra and enhanced oscillator strengths, with the magnitude of the spectral shifts being more substantial in the presence of the ethynyl functionalities. Spectral features of the arylethynyl porphyrin bearing p-dimethylamino substituents closely resemble those previously classified as "hyperporphyrin spectra" and are indicative of excited-state charge-transfer character. Protonation of both series of porphyrins results in reduced fluorescence lifetimes and enhanced nonradiative decay rates, and the impact of protonation on these parameters is attenuated in the presence of the arylethynyl functionalities. Our results coupled with previous structural data showing that arylethynyl porphyrins exhibit less structural distortion upon diacid formation relative to H(2)TPP further substantiate the proposal that significant alteration of porphyrin photophysical properties upon diacid formation can be attributed to nonplanar structural distortions induced by protonation.     

Ion-association aggregation of an anionic porphyrin at the liquid/liquid interface studied by second harmonic generation spectroscopy

Interfacial ion-association adsorption and aggregation of a water-soluble porphyrin, tetrakis(4-sulfonatephenyl)porphyrin (TPPS) diacid, which was promoted by a cationic cetyltrimethylammonium ion (CTA(+)), was studied by second harmonic generation (SHG) spectroscopy. Comparing the interfacial SH spectrum with the transmission absorption spectrum of TPPS in the aqueous solution elucidated the aggregation behavior of TPPS at the heptane/water interface. The time-dependent SHG spectra for TPPS aggregation and the interfacial tension lowering in the presence of CTA(+) were discussed on the basis of an electrostatic adsorption model. Then, it was suggested that TPPS diacid was highly concentrated by the ion-association with CTA(+) at the interface, which was the intermediate state before the final aggregated state.     

Coordination Chemistry‐Assembled Multicomponent Systems Built from a Gable‐Like Bis‐Porphyrin: Synthesis and Photophysical Properties

Multiporphyrinic assemblies were quantitatively formed, in one step, from a gable‐like zinc(II) bis‐porphyrin ZnP₂ and free‐base porphyrins bearing pyridyl groups. The different fragments are held together by axial 4′‐N(pyridyl)–Zn interactions. Formation of a macrocycle ZnP₂?(4′‐cisDPyP) and a bis‐macrocycle (ZnP₂)₂?(TPyP) is discussed. The macrocycle and the bis‐macrocycle were crystallized and studied by X‐ray diffraction, which confirmed the excellent complementarity between the various components. Spectrophotometric and spectrofluorimetric titrations and studies reveal high association constants for both multiporphyrinic assemblies due to the almost perfect geometrical match between the interacting units. As expected, energy transfer from the zinc porphyrin component to the free‐base porphyrin quenches the fluorescence of the zinc porphyrin components in both compounds. But while in ZnP₂?(4′‐cis DPyP) sensitization of the emission of the free‐base porphyrin was observed, in (ZnP₂)₂?(TPyP) excitation of the peripheral Zn porphyrin units does not lead to quantitative sensitization of the luminescence of the free‐base porphyrin acceptor. An unusual HOMO–HOMO electron transfer reaction from ZnP₂ to the excited TPyP unit was detected and studied.     

Synthesis of oligo(p-phenylene)-linked dyads containing free base, zinc(II) or thallium(III) porphyrins for studies in artificial photosynthesis

A series of (p-phenylene)_n-linked meso-mesityl-substituted porphyrin dyads (n=2-4) was prepared via Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base porphyrin dyads were demetalated. The series of free base porphyrin dimers (n=1-4), four other porphyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl meso substituents), and several benchmark monomers were converted to the thallium(III)chloride complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and benchmark monomers have been prepared.     

TRANSFER OF EXCITATION ENERGY BETWEEN PORPHYRIN CENTERS OF A COVALENTLY-LINKED DIMER*

Abstract— Three covalently-linked porphyrin hybrid dimers were synthesized, each containing a metallotetraarylporphyrin [Zn(II), Cu(II), or Ni(II)], and a free base tetraarylporphyrin. Transfer of singlet excitation energy from the metalloporphyrin center to the free base porphyrin center was determined by measuring fluorescence properties. The Zn hybrid dimer displayed excellent intramolecular transfer of energy ( 85%) from the excited singlet state of the Zn(II) chromophore to the free base chromophore. No evidence for such transfer of the excited singlet state energy was found in the Ni(II) or Cu(II) analogues. From our experimental data, the fluorescence quantum yield of the Zn hybrid dimer was the same as for the free base monomer porphyrin (0.11; Seybold and Gouterman, 1969). Thus, the covalent attachment of another fluorescent porphyrin center effectively doubled the antenna size without decreasing the quantum yield even though the fluorescence quantum yield of the Zn(II) containing monomer was substantially less (0.03, according to Seybold and Gouterman, 1969) than that of the free base porphyrin. The donor-acceptor distance and the rate constant for energy transfer were calculated using the Forster equation. Assuming random orientation, a donor-acceptor distance of 15 Å was calculated with an associated rate constant (k_ci) for energy transfer of 1.9 ± 10₉ s_–1.