On the dynamics of the TPPS4 aggregation in aqueous solutions: successive formation of H and J aggregates

The dynamics of aggregation of meso-tetrakis (p-sulfonatofenyl) porphyrin (TPPS4) in function of its concentration, pH and ionic strength was studied by optical absorption, fluorescence and resonance light scattering (RLS) techniques. In the region of pH, where TPPS4 exists in biprotonated form, the addition of NaCl induces the TPPS4 aggregation due to the formation of the "cloud" of counter ions around the TPPS4 molecule thus reducing electrostatic repulsion between the porphyrin molecules. The formation of this "cloud" shifts the pKa value to acid region (from 5.0 in the absence of salt to 4.5 at [NaCl] = 0.4 M), reduces the TPPS4 absorption in all spectral range and quantum yield and lifetime of fluorescence (from 0.27 to 0.17 and from 4.00+/-0.04 to 3.00+/-0.03 ns in the absence of salt and in the presence of NaCl, respectively). The aggregation process involves two successive stages: initially H aggregates are formed, which in time are transformed in J ones. The existence of these two stages was confirmed by the fluorescence and RLS data. The kinetics of the formation of J aggregates is characterized by the induction time t1 and the average growth time t2, which depend on both TPPS4 and salt concentrations. The induction period t1 appears as a result of initial formation of H aggregates and their successive transformation in J ones. At very high TPPS4 concentrations, the J aggregates are united in more complex structures such as hollow cylinders or helixes.     

Studies on the effects of metal ions and counter anions on the aggregate behaviors of meso-tetrakis(p-sulfonatophenyl)porphyrin by absorption and fluorescence spectroscopy

The aggregation behaviors of meso-tetrakis(p-sulfonatophenyl)porphyrin (TPPS) in the function of metal ions and their counter anions (Cl(-), SO(4)(2-), and NO(3)(-)) were investigated by absorption, fluorescence spectroscopy and resonance scattering spectrum. It was shown that the TPPS J-aggregates could be effectively promoted by metal ions under lower ionic strength. Moreover, the prominent effects of counter ions (Cl(-), SO(4)(2-), and NO(3)(-)) on TPPS J- and/or H-aggregate formation at higher ionic strength were observed. These results suggested that the counter anions play a significant role in the formation of TPPS J- and/or H-aggregates and their conversion each other. Very interestingly, the absorption spectrum of metal ions investigated except for Co(2+) leaves a WINDOW from ca. 450 to 550nm centered at 490nm in which the absorption of Cu(2+) or Ni(2+) ions per se was very weak. The spectrum window might be really significant in avoiding possible spectrum interferences when porphyrins are chosen as spectrometric reagents for the determination of metal ions based on J-aggregation.     

Exciton coupling of tetra(p-hydroxyphenyl)porphyrin controlled by substituents of counterions in Triton X-100 micellar solution

The interactions of nonionic meso-tetra(p-hydroxyphenyl)porphyrin (THPP) with CX3COOH (X = F, Cl, Br) in Triton X-100 (TX) micellar solution have been investigated by optical absorption, resonance light-scattering, and fluorescence spectroscopies. The double red-shifted absorption bands and strong resonance light scattering (RLS) signal imply that the assemblies induced by trihalo acetic acids belong to J-aggregates. The fluorescence of porphyrin is quenched due to the aggregate formation. The kinetics of assemblies trigged by CBr3COOH is studied via stopped-flow techniques. No characteristics of autocatalyzed reactions are observed, and there is only a log phase. The nature of the exciton coupling of transition dipole moment can be systematically changed by the haloid substituents of the organic counteranion.     

Porphyrin J-aggregates stabilized by ferric myoglobin in neutral aqueous solution

J-aggregates of a diacid form (H4TPPS2-) of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (H2TPPS4-) were stabilized by binding with ferric myoglobin (metMb) in aqueous solution at neutral pH. The J-aggregates gradually dissociated to monomeric H2TPPS(4-). The average half-lifetime (t1/2) of the J-aggregates in the presence of sufficient amounts of metMb was ca. 3 h in phosphate buffer at pH 7.0 and 25 degrees C. The stabilization of the J-aggregate by metMb is ascribed to encapsulation and fixation of an edge-to-edge structure of the J-aggregate by the relatively rigid protein molecules. The secondary structure of metMb was altered in some extent in the presence of an excess amount of the J-aggregates while no effect on denaturation of metMb was observed with the H2TPPS(4-) monomer or polyacrylate. The hydrophobic nature of the J-aggregate seems to play an important role for denaturation of metMb. The ability of denatured metMb to bind the azide anion was higher than that of natural metMb. The denaturation of metMb by the J-aggregates seems to induce surfacing of hemin leading to an entropy gain in coordination of the N3(-) anion to the iron(III) center.     

Study on the Association Phenomenon of Cyclodextrin to Porphyrin J-aggregates by NMR Spectroscopy

The nuclear magnetic resonance (NMR) spectroscopy demonstrated that the inclusion complexes of meso-tetrakis- (p-sulfonatophenyl) porphyrin (TPPS) with β-, Hydroxypropyl-β- and Methyl-β-cyclodextrin (β-, HP-β- and Me-β-CD) are formed, which resulted in the dissociation of TPPS J-aggregates efficiently under certain acidity. There are no significant differences in binding affinities and basic complexation mechanisms between TPPS and β-cyclodextrin (β-CD) or hydroxypropyl-β-cyclodextrin (HP-β-CD), i.e. porphyrin is included through the wide side of the cavity of β-CD or HP-β-CD. Alternatively, porphyrin is included through the narrow side of the Me-β-CD cavity.     

四-（4-吡啶基）卟啉二酸聚集体的共振拉曼光谱

研究了近激子吸收带激发下四-（4-吡啶基）卟啉二酸（H8TPyP^6＋）聚集体的共振拉曼光谱。测量了H8TPyP^6＋单体和聚集体的紫外可见吸收谱和共振光散射光谱．在氘代位移的基础上结合相关体系振动光谱研究,对测得的H8TPyP^6＋单体和聚集体的拉曼谱带进行了指认．聚集体的形成导致H8TPyP^6＋的卟啉环CC／CN面内伸缩振动向低波数方向位移2-6cm^-1,而卟啉环鞍形面外振动带向高波数方向位移12cm^-1．基于拉曼谱带的强度和频率变化分析了聚集引起的H8TPyP^6＋分了内结构变化和分子间氢键作用．     

Counteranion dependent protonation and aggregation of tetrakis(4-sulfonatophenyl)porphyrin in organic solvents

The tetrabutylammonium salt of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS) is soluble in dichloromethane, and the general properties of this compound have been investigated as function of various added acids HX (X = Cl, Br, I, CF(3)COO, CF(3)SO(3), TFPB) through UV-vis absorption spectroscopy, steady state fluorescence emission, and resonance light-scattering (RLS) techniques. Upon addition of HX, the initial monomeric free base TPPS is readily converted in an aggregated species, whose spectroscopic features are independent of the nature of the counteranion X. All the spectroscopic evidence suggest a J-type arrangement of chromophores in this aggregate, involving strong hydrogen bonds, electrostatic, and dispersive interactions. In the specific case of chloride and bromide, in the presence of a TBAX excess, the addition of the corresponding acid leads to a monomeric ion-pair between the TBA cations and the diacid TPPS, whose central core is strongly interacting with the halide. On further increasing the acid concentration in these latter solutions, fully protonated species are formed that eventually start to aggregate.     

Raman and infrared spectral study of meso-sulfonatophenyl substituted porphyrins (TPPSn,n = 1, 2A, 2O, 3, 4)

Raman and IR spectra of the free base p-sulfonatophenyl and phenyl meso-substituted porphyrins [5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4); 5,10,15-tris(4-sulfonatophenyl)-20-phenyl-porphyrin (TPPS3); 5,10-bis(4-sulfonatophenyl)-15,20-diphenylporphyrin (TPPS2A); 5,15-bis(4-sulfonatophenyl)-10,20-diphenylporphyrin (TPPS2O); and 5-(4-sulfonatophenyl)-10, 15,20-trisphenylporphyrin (TPPS1)] and their N-diprotonated derivatives (porphyrin diacids) were studied. The Raman spectra of the deuterated analogues of these porphyrins, in which the central hydrogen atoms were substituted with deuterium, were also measured. The observed vibrational bands were assigned on the basis of the deuteration shifts and compared with the structural analogues of these compounds. In IR spectra of the free-base porphyrins, the p-sulfonation of phenyl groups results in evident alteration for the phenyl modes and the porphyrin skeleton modes that are strongly coupled with phenyl vibrations. While the p-sulfonation of phenyl groups causes only slight changes for the high-frequency Raman bands (> 850 cm(-1)), dramatic shifts and band splitting were observed in the low-frequency region (< 500 cm(-1)) of Raman spectra. The observed differences of low-frequency Raman spectra were attributed to the alteration of the structure of the porphyrin ring, especially the CalphaCmCalpha bond-angles, by different meso-sulfonatophenyl substitutions. In addition, different packing style of TPPSn molecules in the aggregates is also responsible for the alteration of the vibrational spectra of the aggregated TPPSn.     

Adsorption Behavior of a Water-soluble Porphyrin at the Glass-water Interface as Studied by Synchronous Total Internal Reflection Fluorescence Spectroscopy

Total imernal reflection fluorescence spectroscopy (TIRF) and synchronous scanning technique were combined to study the adsorption behavior of the meso-tetrakis (4-sulfonatophenyl)porphyrin (TPPS) at the glass-water interface without any surfactant. The pH dependence of synchronous fluorescence signal at the interface was analyzed. Both unprotonated (TPPS^4-) and diprotonated (H2TPPS^2-) forms of TPPS were observed at the interface. But the interface favored the adsorption of. The apparent estimated pKa2 value shifted from 5.00 in the bulk solution to 2.7 at the interface. STIRF provides a good technique to study multi-component systems at the interface.     

Influence of hydrogen bonding on excitonic coupling and hierarchal structure of a light-harvesting porphyrin aggregate

Helical porphyrin nanotubes of tetrakis(4-sulfonatophenyl)porphyrin (TSPP) were examined in DCl/D(2)O solution using resonance Raman and resonance light scattering spectroscopy to probe the influence of hydrogen bonding on the excitonic states. Atomic force microscopy reveals similar morphology for aggregates deposited from DCl/D(2)O and from HCl/H(2)O solution. Deuteration results in subtle changes to the aggregate absorption spectrum but large changes in the relative intensities of Raman modes in the J-band excited resonance Raman spectra, revealing relatively more reorganization along lower-frequency vibrational modes in the protiated aggregate. Depolarization ratio dispersion and changes in the relative Raman intensities for excitation wavelengths spanning the J-band demonstrate interference from overlapping excitonic transitions. Distinctly different Raman excitation profiles for the protiated and deuterated aggregates reveal that isotopic substitution influences the excitonic structure of the J-band. The deuterated aggregate exhibits a nearly two-fold increase in intensity of resonance light scattering as a result of an increase in the coherence number, attributed to decreased exciton-phonon scattering. We propose that strongly coupled cyclic N-mers, roughly independent of isotopic substitution, largely decide the optical absorption spectrum, while water-mediated hydrogen bonding influences the further coherent coupling among them when they are assembled into nanotubes. The results show that, similar to natural light-harvesting complexes such as chlorosomes, hydrogen bonding can have a critical influence on exciton dynamics.     

The interaction of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin with surfactants: solubilization and J-aggregates

J-aggregates of 2-hydroquinone-5,10,15,20-tetra(p-hydroxyphenyl)porphyrin (HQTHPP) induced by N-lauroyl sarcosine (SKL) in aqueous neutral solutions have been studied by optical absorption, fluorescence, and resonance light-scattering spectroscopies. As SKL concentration increases, the spectra evolve to reveal the presence of four independent species with relative concentration. The most important species is J-aggregates. The J-aggregates have two strong exciton bands corresponding to the B-band and Q-bands of HQTHPP monomers, and are found to be stable when the surfactant concentration is below 8.0 mmol/L. But above 8.0 mmol/L, the J-aggregates dissolve gradually into another species: porphyrin monomers. The total fluorescence of HQTHPP is quenched due to the aggregate formation. A strong and sharply peaked resonance light-scattering signal (>1800 counts/s, centered at 490 nm) is observed just slightly to the red of the J-aggregate absorption maximum. In the case of cetyltrimethyl-ammonium bromide, increasing surfactant concentrations have only shown to favor solubilization of porphyrin monomers. Evidently, the nature of polar headgroups of surfactants influences the tendency of THPP to aggregate.     

Kinetic effects of tartaric acid on the growth of chiral J-aggregates of tetrakis(4-sulfonatophenyl)porphyrin

The kinetics of growth for chiral J-aggregates of H(4)TPPS(4) porphyrin have been investigated under different experimental conditions in the presence of tartaric acid. The observed rate constants and the anisotropy factor g show a defined dependence on the enantiomer used as a chiral templating agent.     

Strong enhancement of the two-photon absorption of tetrakis(4-sulfonatophenyl)porphyrin diacid in water upon aggregation

A strong enhancement of the two-photon absorption (TPA) cross section of tetrakis(4-sulfonatophenyl)porphyrin diacid (H(4)TPPS(2-)) at various wavelengths when a J-type aggregate is formed in water with respect to the one observed for the H(4)TPPS(2-) monomer in a mixture of water, dimethyl sulfoxide (DMSO), and urea is presented. The TPA properties are characterized by the open aperture Z-scan technique and the ultrafast two-photon absorption spectroscopy with white light continuum probe (TPA-WLCP) technique. The observed enhancement is discussed in terms of possible electronic cooperative effects in the aggregate.     

Electric field-controlled dissociation and association of porphyrin J-aggregates in aqueous solution

The electrooptic effects of porphyrin J-aggregates of tetraphenyl porphyrin tetrasulfonic acid (TPPS) in aqueous solution were studied using electroabsorption (EA) spectroscopy. When the J-aggregates were three-dimensionally distributed, the EA spectra exhibited broadening in the exciton band. When a DC or AC electric field was applied for a long time, the J-aggregates with KCl were dissociated into monomers via N-mers (N = 2-4) as intermediate states, while those without KCl had an increase in aggregation. The EA spectra showed a red shift in the exciton band for N-mers, which indicates that N-mers are isolated microaggregates with a coherent aggregation number N, and isolated microaggregates have not been microscopically or spectrally observed until now. The estimated third-order nonlinear optical susceptibility χ((3)) for EA spectra in aqueous solution was 10(4) times larger than that in a polymer film. The molecular rearrangement model was applied to a variety of orientational distributions and the results were explained fairly well. The contribution of the electric double layer is the most probable reason for the large enhancement of χ((3)) for the solution sample. The dynamic equilibrium between two types of monomers, J-aggregates of various aggregation numbers and cations such as K(+) and H(+) was investigated to reveal that K(+) is more loosely bound to the constituent monomers in J-aggregates than H(+). Equilibrium equations also show that well-grown aggregates with N > 15 tend to dominate in a solution of J-aggregates, which explains why only well-developed aggregates can be observed spectroscopically.     

Interaction of monosulfonate tetraphenyl porphyrin (H2TPPS1) with plant-esterase: determination of the binding mechanism by spectroscopic methods

The interaction of monosulfonate tetraphenyl porphyrin (H(2)TPPS(1)) with plant-esterase was investigated using fluorescence and UV-vis absorption spectroscopy. Fluorescence quenching, from which the binding parameters were evaluated, revealed that the quenching of the esterase by H(2)TPPS(1) resulted from the formation of a dye-esterase complex. According to the modified Stern-Volmer equation, the effective quenching constants (K(a)) between H(2)TPPS(1) and plant-esterase at four different temperatures (297 K, 300 K, 303 K, and 306 K) were obtained to be 14.132×10(5), 5.734×10(5), 2.907×10(5), and 2.291×10(5) M(-1), respectively. The thermodynamic parameters, enthalpy change (ΔH) and entropy change (ΔS) for the reaction were calculated to be -181.67 kJ M(-1) and -0.49 kJ M(-1)K(-1), indicating that van der Waals force and hydrogen bonds were the dominant intermolecular force in stabilizing the complex. Site marker competitive experiments showed that the binding of H(2)TPPS(1) to plant-esterase primarily took place in the active site. The binding distance (r) was obtained to be 5.99 nm according to F?rster theory of non-radioactive energy transfer. The conformation of plant-esterase was investigated by synchronous fluorescence and UV-vis absorption spectroscopy, and the results confirmed some micro-environmental and conformational changes of plant-esterase molecules.     

Synthesis and characterization of a water-soluble porphyrin with a cyclic sulfone

Water-soluble sulfonated tetraarylporphyrins are studied in a wide variety of contexts including as analytical reagents and as possible agents in cancer photodynamic therapy as well as in antiviral and antidiabetic applications. Herein, we report the first synthesis of a pentasulfonated porphyrin bearing an internal cyclic sulfone ring. Treatment of 5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (TPPS4) with fuming H₂SO₄ gave a structure consistent with initial sulfonation followed by dehydration to give a sulfone bridge between an ortho-position of one of the phenyl groups and a β-pyrrole position on the porphine ring (TPPS4Sc). The structure was established by electrospray mass spectrometry and ¹H NMR. The Soret UV-visible absorption is red shifted by about 32 nm compared to that of TPPS4.     

Study on the supramolecular system of meso-tetrakis (4-sulfonatophenyl) porphyrin and cyclodextrins by spectroscopy

The ability of beta-cyclodextrin (beta-CD), sulfurbutylether-beta-CD (SBE-beta-CD) and hydroxypropyl-beta-CD (HP-beta-CD) to break the aggregate of the meso-Tetrakis (4-sulfonatophenyl) porphyrin (TPPS4) and to form 2:1 inclusion complexes has been studied by adsorption and fluorescence spectroscopy. The formation constants are calculated, respectively by fluoremetry, from which the inclusion capacity of different CDs is compared and the inclusion mechanism of charged-beta-CD (SBE-beta-CD) is quite different from that of parent beta-CD. At lower pH, the complexation between HP-beta-CD and H2TPPS(2+)4 (the form of the diprotonated TPPS4) hampers the continuous protonation of the pyrrole nitrogen of TPPS4 and the hydrophobic cavity may prefer to bind an apolar neutral porphyrin molecule. 1HNMR data support the inclusion conformation of the porphyrin-cyclodextrin supramolecular system, indicating the interaction of meso-phenyl groups of TPPS4 with the cavity of CDs. For this host-guest inclusion model, cyclodextrin, being regarded as the protein component, which acts as a carrier enveloping the active site of heme prosthetic group within its hydrophobic environment, provides a protective sheath for porphyrin, creating artificial analogues of heme-containing proteins. However, the TPPS4, encapsulated within this saccharide-coated barrier, its physico-chemical, photophysical and photochemical properties changed strongly.     

新型双阳离子卟啉的聚集行为及超声诱导的转换

合成了一种新型水溶性双阳离子卟啉PP1,该化合物在结构上同时具有给电子和拉电子基团的分子识别位点.PP1在其自身浓度低于亚微摩尔/升的条件下就可以自发地形成J-聚集体,通过紫外光谱、共振光散射光谱和荧光光谱等手段表征,并测得了其临界聚集浓度.随着自身浓度进一步升高,PP1逐渐转向H-聚集体.另外,一定浓度下PP1的H-聚集能够被超声波诱导而转化为J-聚集.     

水溶液中meso-四(4-磺苯基)卟啉二聚体的形成和伏安行为研究

本文研究了水溶液中meso-四(4-磺苯基)卟啉(TPPS)二聚体(Dimer)的各种影响因素和它的电化学性质。提出了二聚体的模型, 说明了水溶性金属卟啉(Cu^2+,Zn^2+, Mn^2+-TPPS)循环伏安图上的一对小尖峰是二聚体在汞电极上吸附还原和氧化的结果。     

Counterion dependent dye aggregates: nanorods and nanorings of tetra(p-carboxyphenyl)porphyrin

Atomic force microscopy (AFM) of porphyrin aggregates formed on silica from acidic aqueous solution is used to investigate the basis for the previously reported counterion dependence of the optical spectra of aggregates of H(2)TCPP(2+), the diacid form of tetra(p-carboxyphenyl)porphyrin (TCPP). Resonance light scattering confirms the presence of excitonically coupled porphyrin aggregates in solutions of H(2)TCPP(2+) in both aqueous HCl and HNO(3). Aggregates formed in aqueous HNO(3) solutions show resonance light scattering (RLS) at wavelengths within both the H and J aggregate absorption bands and are imaged on the surface of silica as nanorods about 3 to 4 nm in height. H(2)TCPP(2+) aggregates in aqueous HCl solution exhibit RLS when excited within the blue-shifted Soret band (H band) and produce AFM images on silica of ring-shaped structures ranging from about 200 to 2000 nm in diameter. Fluorescence excitation and emission spectra reveal quenching of the Q-band emission in the aggregates at a pH less than 1 and confirm the existence of a single species, assigned to a dimer, at a pH just above 1. The morphology of the nanostructures as revealed by AFM provides insight into the structural basis for the counterion-dependent optical properties of H(2)TCPP(2+) aggregates.