Tetrakis 4-sulfonatophenyl Porphyrin Research Articles

Paper-Based Heavy Metal Sensors from the Concise Synthesis of an Anionic Porphyrin: A Practical Application of Organic Synthesis to Environmental Chemistry

Tetrakis(4-sulfonatophenyl)porphyrin (TSPP) was immobilized on patterned paper and used as a sensor for heavy metal ions in an advanced organic chemistry course. The resulting sensor could detect Hg2+ and Cd2+ ions colorimetrically, while Cu2+ ion resulted in fluorescence quenching, thus demonstrating a multiplex capability of this paper-based sensor. From the synthesis of the porphyrin to the fabrication of the sensor, advanced undergraduate chemistry students gained first-hand experience with a classical organic synthesis, and also witnessed its application within 2–3 full-day laboratory sessions. This experiment is a good demonstration of how an easily synthesized compound can be exploited to tackle an important problem in real-world situations.

Sulfonated porphyrin doped polyaniline nanotubes and nanofibers: synthesis and characterization

The nanotubes and nanofibers of polyaniline (PANI) were successfully synthesized by a template-free and interfacial polymerization method respectively in the presence of tetrakis(4-sulfonatophenyl)porphyrin (TSPP) as a dopant. The tubular and fibrous morphologies of the TSPP–PANI were confirmed by TEM images. The morphology of TSPP–PANI can be changed from nanotube to cauliflower by simply changing the volume ratio of the dopant to the aniline monomer as confirmed by SEM images. It was observed that the formation of nanotubes (by the template-free method) was independent of the dopant, but the dopant was associated with interfacial polymerization for the formation of nanofibers. It might be the electrostatic and hydrophobic interactions between the water dispersible porphyrin complex [TSPP–(NH4)2S2O8] and the dimer cation-radical surfactant which are responsible for the formation of nanofibers. The resulting materials were also characterized by conductivity, solubility, FTIR and UV-vis spectroscopy, X-ray diffraction and cyclic voltammetry.

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.

Continuous real-time monitoring of cationic porphyrin-induced photodynamic inactivation of bacterial membrane functions using electrochemical sensors

We analysed the porphyrin-induced photodynamic inactivation of the membrane functions of bacteria through the in situ monitoring of changes in respiration rates, membrane permeability and membrane potential, using electrochemical sensors, such as oxygen, K(+) and tetraphenylphosphonium (TPP(+)) electrodes. We used two cationic porphyrins, tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TTMAPP) and tetrakis(4-N-methylpyridinium)porphyrin (TMPyP), along with an anionic porphyrin, tetrakis(4-sulfonatophenyl)porphyrin (TSPP), as a negative control. TTMAPP and TMPyP inhibited the respiration of bacteria within minutes of photo-irradiation at a concentration of 1 μM, where the survival of bacteria decreased, while TSPP did not affect the bacteria. The respiration of Staphylococcus aureus cells (Gram-positive bacterium) was more strongly inhibited than that of Escherichia coli cells (Gram-negative bacterium). Increasing the concentration of porphyrin strengthened the respiratory inhibition. Although TTMAPP increased the permeability to K(+) of the cytoplasmic membranes of bacteria, the change was relatively slow. Cationic porphyrins, showing the strong respiratory inhibition of S. aureus cells, induced the dissipation of membrane potential within minutes of photo-irradiation, in accord with the time traces of respiratory inhibition. Such a correlation strongly supported that porphyrin-induced photo-inactivation of bacteria involved rapid damage to the energy-producing system of bacteria induced by inhibition of the respiratory chain, leading to a dissipation of membrane potential. These results are discussed in connection with the ability of porphyrins to generate singlet oxygen and bind to the bacterial cell envelope.

Molecular organization and effective energy transfer in iridium metallosurfactant–porphyrin assemblies embedded in Langmuir–Schaefer films

Mixed Langmuir monolayers and Langmuir-Schaefer (LS) films containing the cationic metallosurfactant bis(2-phenylpyridine)(4,4'-diheptadecyl-2,2'-bipyridine)-iridium(III) chloride (Ir-complex) and the anionic tetrakis(4-sulfonatophenyl)porphyrin (TSPP) in 4:1 molar ratio have been successfully prepared by the co-spreading method at the air-water interface. The presence of both luminescent species at the interface, as well as the organization of the TSPP underneath the Ir-complex matrix in Langmuir and LS films, is inferred by surface techniques such as π-A isotherms, reflection spectroscopy, Brewster angle microscopy (BAM) and UV-visible absorption spectroscopy. A red-shift in the absorption band of the porphyrin under the compression of the mixed monolayer suggests the J-aggregation of the TSPP under the Ir-complex matrix. To date, this is the first report of Langmuir and/or LS films containing these two types of species together. Furthermore, the intermolecular energy transfer between Ir-complex and TSPP molecules in solution and in transferred mixed films is investigated through steady-state fluorescence and lifetime measurements. These results indicate that effective intermolecular energy transfer occurs from the Ir-complex to the TSPP molecules in LS films. The influence of the spatial proximity of donor and acceptor molecules has been studied by the insertion of lipid interlayers among them.

Tetrakis(4-sulfonatophenyl)porphyrin fluorescence as reporter of human serum albumin structural changes induced by guanidine hydrochloride

The interaction of the drug carrier protein human serum albumin (HSA) with the ionic, free base porphyrin tetrakis(4-sulfonatophenyl)porphyrin (TSPP) was investigated under chemical denaturation conditions using guanidine hydrochloride (Gdn-HCl) in aqueous solution at pH 7 and 2.5. Protein stability was studied by fluorescence spectroscopy using intrinsic tryptophan fluorescence, whereas far-UV circular dichroism gave information regarding conformational changes. Steady-state and time-resolved fluorescence as well as extinction and induced visible CD of TSPP were also monitored in the presence of the denaturant. The addition of 1.0 M Gdn-HCl inhibited the FRET process between the sole tryptophan residue of HSA and the porphyrin as inferred by an increase in the intrinsic fluorescence of the former together with a drop in the fluorescence of the latter. Simultaneously, an induced bisignate CD band was detected in the Soret region of TSPP extinction following the changes in the monomer ↔ aggregate equilibrium of TSPP. The features in the extinction spectra pointed to the formation of J-aggregates at pH = 2.5 and were confirmed by fluorescence lifetime measurements. At pH = 7, no TSPP dimers were detected in the absence of the protein or in the presence of native HSA. However, H-dimers or higher aggregates of TSPP associated to HSA were induced at concentrations of Gdn-HCl below 2 M. The main unfolding transition probed by HSA intrinsic fluorescence took place between 2 and 3 M Gdn-HCl at pH = 7, whereas at pH = 2.5 it was detected only above 2.8 M Gdn-HCl, coinciding with TSPP release into solution which occurs at high denaturant concentration for both pH studied. The results suggest that the chemical unfolding of HSA is a multistep process. The free base porphyrin contributes to an increase in the protein stability, particularly important under acidic conditions, where the protein is known to be in an expanded form in the absence of TSPP. The analysis of TSPP fluorescence fluctuations in the autocorrelation functions obtained using fluorescence correlation spectroscopy (FCS) in the presence of HSA at different denaturant concentrations showed that the porphyrin only interacts with the native form of the protein. Both fluorescence and circular dichroism data confirmed that in the noncovalent complex HSA–TSPP the free base porphyrin can act as a reporter of the protein structural changes induced either by pH or chemical denaturation.

Resonance Raman Spectroscopy of Helical Porphyrin Nanotubes

We report polarized resonance Raman data of tetrakis(4-sulfonato)phenyl porphyrin (TSPP) aggregates in solution and deposited on Au(111) at wavelengths resonant with the red-shifted (J-band) and blue-shifted (H-band) components of the split Soret (B) band. We also report scanning tunneling microscopy (STM) images which reveal that the aggregate on Au(111) is a nanotube with a 2 nm wall thickness which tends to flatten on the substrate. Relative Raman intensities and their dependence on polarization of the incident and scattered light are found to vary greatly for H- and J-band excitation, revealing a much greater degree of coherence for the J-band, in agreement with the resonance light scattering spectrum. The J-band transition is found to have transition moment components both parallel and perpendicular to the long axis of the nanotube, consistent with a helical nanotube structure. The intensity increase of the Q-band on aggregation and the weak intensity of the H-band in both the absorption and the resonance light scattering spectra are explained by vibronic B-Q coupling, which is permitted in the lowered site symmetry of the aggregate. The resonance Raman data presented here provide insight into the molecular basis for the hierarchal structure of the aggregate.

Complex formation of tetrakis(4-sulfonatophenyl)porphyrin with γ-cyclodextrin, phenylalanine, and tryptophan in aqueous solution

In pH 10.3 buffer, in which phenylalanine and tryptophan are in an anionic form, the interactions of tetrakis(4-sulfonatophenyl)porphyrin (TSPP) with γ-cyclodextrin (γ-CD) and phenylalanine (or tryptophan) have been examined by means of absorption and fluorescence spectroscopy. A 1:1 inclusion complex is formed between TSPP and γ-CD. TSPP forms 1:2 complexes with l- and d-phenylalanine (LPhe and DPhe), while TSPP forms 1:1 complexes with l- and d-tryptophan (LTrp and DTrp). In TSPP solution containing γ-CD and LPhe (or DPhe), the 1:1:2 γ-CD–TSPP–LPhe (or –DPhe) inclusion complex is formed, while the 1:1:1 γ-CD–TSPP–LTrp (or –DTrp) inclusion complex is formed for LTrp (or DTrp). The equilibrium constants for the formation of the complexes have been evaluated from the fluorescence intensity change of TSPP. The equilibrium constants are nearly the same for the optical isomers of phenylalanine and tryptophan, respectively, indicating that the optical isomers are not discriminated through the complexation. For the LPhe complexes, the equilibrium constants have also been evaluated at a fixed ionic strength of 0.2 mol dm−3 using NaCl. 3-Phenyl-1-propanol and l-phenylalaninol, which are analogous to phenylalanine in molecular structure, have been examined for the complexation with TSPP and γ-CD. In contrast to phenylalanine, the stoichiometries of their binary complexes with TSPP and their ternary inclusion complexes with γ-CD and TSPP are 1:1 and 1:1:1, respectively.

Reversible Collapse of Insoluble Monolayers: New Insights on the Influence of the Anisotropic Line Tension of the Domain

In this paper, we study the collapse of a mixed insoluble monolayer formed by a cationic matrix, dioctadecyl-dimethylammonium bromide (DOMA), and a tetra-anionic porphyrin, tetrakis(4-sulfonatophenyl)porphyrin (TSPP), in a molar ratio TSPP/DOMA = 1:4. During the collapse of this system, we visualized the formation of circular domains consisting exclusively of trilayer, although the domains coalescence was not observed. The coexistence of trilayer and monolayer at the final step of the collapse cannot be interpreted exclusively in terms of a thermodynamic phase equilibrium, intervening as an additional factor the anisotropic line tension of the domain. A high line tension implies a high resistance to the domain deformation, and the anisotropy of the line tension implies the lack of coalescence between these domains, which has been experimentally observed by Brewster angle microscopy for us. Under these circumstances, the domains of collapsed material could enclose monolayer regions where the local surface pressure drops thus stopping the collapse process. The collapse of the TSPP/DOMA system is reversible, that is, the return of the three-dimensional material to the monolayer fits into a simple kinetics according to the nucleation-growth-collision theory. As for the collapse, the reverse process is also affected by the line tension of the domains. This paper relates the high line tension and the anisotropic line tension of a given domains with the reversible nature of the collapse process.

Aggregation behavior of aqueous tetrakis(4-sulfonatophenyl)porphyrin in the presence of 1-butyl-3-methylimidazolium tetrafluoroborate

Due to their unusual properties the role of ionic liquids (ILs) in affecting aqueous aggregation has become a topic of immense interest. Depending on the pH and the ionic strength of the solution many common porphyrins form J-aggregates in the presence of appropriate external additives. Effect of addition of a ‘hydrophilic’ IL, 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4]) on aqueous aggregation of a common porphyrin, tetrakis(4-sulfonatophenyl)porphyrin (TSPP), is investigated at different pH in the presence of varying concentration of [bmim][BF 4] using molecular absorbance and steady-state fluorescence. The kinetics of the interconverting species in the presence of [bmim][BF 4] within aqueous TSPP at different pH is also studied. It is observed that the low amount of [bmim][BF 4] ( ca. 0.221–0.442 M or ca. 4.5–9.0 vol.%) favors the formation of J-aggregates at low solution pH; further increasing [bmim][BF 4] concentration leads to the destabilization of J-aggregates due to the deprotonation of TSPP from H 4TSPP 2− to H 2TSPP 4−, which, in turn, gets involved in formation of TSPP–[bmim][BF 4] complex. J-aggregation at low pH in the presence of [bmim][BF 4] is demonstrated to be significantly more efficient as compared to that in the presence of NaBF 4. Presence of [bmim][BF 4] at low pH facilitates the conversion of monomeric species to the J-aggregates which follows pseudo first-order kinetics with rate constants in agreement with experimental observations. Unique and effective role of IL [bmim][BF 4] in modifying aggregation behavior of aqueous TSPP is clearly demonstrated.

Interactions of Tetrakis(4-sulfonatophenyl)porphyrin with γ-Cyclodextrin and Alkyltrimethylammonium Bromides in Aqueous Solutions

Tetrakis(4-sulfonatophenyl)porphyrin (TSPP) forms complexes with octyltrimethylammonium bromide (OTMA) and hexyltrimethylammonium bromide (HTMA) in pH 7.3 buffers. At low concentrations of OTMA (HTMA), a 1:1 TSPP–OTMA complex is formed. As the OTMA (HTMA) concentration is increased, a 1:2 TSPP–OTMA (HTMA) complex is also formed. The equilibrium constants for the formation of the TSPP–OTMA (HTMA) complexes have been evaluated from a simulation of the observed fluorescence intensity data. In the induced circular dichroism spectrum, the signal intensity of TSPP in aqueous solutions containing both γ-CD and OTMA has been similar to that containing only γ-CD, suggesting the formation of the 1:1:1 γ-CD–TSPP–OTMA (HTMA) inclusion complex. Capillary electrophoretic study has exhibited the formation of the 1:1 TSPP–OTMA (HTMA) complex, although the 1:2 TSPP–OTMA (HTMA) complex could not be observed, probably because the OTMA (HTMA) concentration used was low. The equilibrium constants for these 1:1 complexes have been evaluated from the variation in the electrophoretic mobility. The equilibrium constant for the formation of the 1:1:1 γ-CD–TSPP–OTMA or γ-CD–TSPP–HTMA complex has been evaluated from a simulation of the electrophoretic mobility change in TSPP solution containing γ-CD and OTMA or HTMA, although the equilibrium constants for the ternary inclusion complexes could not be evaluated using the fluorescence method due to the small fluorescence intensity change.

Inclusion Complexes of Cyclodextrins with Tetrakis(4-carboxyphenyl)porphyrin and Tetrakis(4-sulfonatophenyl)porphyrin in Aqueous Solutions

In neutral and alkaline solutions, tetrakis(4-carboxyphenyl)porphyrin (TCPP) and tetrakis(4-sulfonatophenyl)porphyrin (TSPP) form 1:1 and 2:1 host–guest inclusion complexes with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), and 6-deoxy-6-diethylamino-β-CD (DEA-β-CD), except for DEA-β-CD in alkaline solution. On the other hand, TCPP and TSPP form only 1:1 inclusion complexes with 6-deoxy-6-dihexylamino-β-CD (DHA-β-CD). The limited solubilities of DEA-β-CD in alkaline solution and DHA-β-CD are likely responsible for no observation of the 2:1 inclusion complex containing DEA-β-CD in alkaline solution and that containing DHA-β-CD. The equilibrium constants (Ks) of TCPP and TSPP for the formation of the inclusion complexes have been estimated from the absorption and/or fluorescence intensity changes in neutral and alkaline solutions. The K2 values, which are the equilibrium constants for the formation of the 2:1 host–guest inclusion complex from the 1:1 inclusion complex, are about one tenth the corresponding K1 values, except for the α-CD–TSPP system in alkaline solution. In neutral solution, where DEA-β-CD and DHA-β-CD are in protonated forms, the electrostatic force operates between DEA-β-CD (DHA-β-CD) and TCPP (TSPP), leading to the greater K values than those in alkaline solution, where DEA-β-CD and DHA-β-CD exist as neutral species.

Photocontrolled release and uptake of a porphyrin guest by dithienylethene-tethered beta-cyclodextrin host dimers.

Two photoswitchable dithienylethene-tethered beta-cyclodextrin dimers were synthesized to function as host molecules with an externally controllable binding affinity. The cyclodextrin cavities of these dimers are linked through their secondary sides by a photochromic dithienylethene unit that is connected to the secondary rim either directly (4) or through propyl spacers (9). Irradiation with light switches these dimers between a relatively flexible (open) and a rigid (closed) form. The binding properties of the dimers depend on the configuration of the dithienylethene spacer, as is shown by microcalorimetry performed with tetrakis-sulfonatophenyl porphyrin (TSPP) as a guest molecule. The differences in binding properties are most pronounced for the more rigid dimer 4, which binds TSPP 35 times more strongly in the open form (4 a) than in the closed form (4 b). The values found for the enthalpy of binding (deltaH degrees ) indicate that this difference in binding is due to the loss of cooperativity between the two beta-cyclodextrin cavities in the closed form. Molecular modeling shows that 4 b is not able to bind TSPP effectively in both cyclodextrin cavities. The open and closed forms of the more flexible dimer 9 show no substantial difference in their binding of TSPP. Thermodynamic values indicative of strong binding of TSPP by two beta-cyclodextrin cavities were measured for both forms of the dimer, and molecular modeling confirms that both are flexible enough to tightly bind TSPP. The binding differences between the forms of dimer 4 allow the photocontrolled release and uptake of TSPP, which renders control of the ratio of complexed to free TSPP in solution possible.

Effects of cyclodextrins on the complexation between Methylene Blue and tetrakis(4-sulfonatophenyl)porphyrin in aqueous solutions

In aqueous solutions buffered at pH 10.1, Methylene Blue (MB) forms a complex with tetrakis(4-sulfonatophenyl)porphyrin (TSPP). The equilibrium constant for the formation of the MB–TSPP complex has been evaluated to be 2.35×10 5 mol −1 dm 3 from the fluorescence quenching of MB by TSPP. Effects of α-, β-, and γ-cyclodextrin (CD), and heptakis(2,3,6-tri- O-methyl)-β-cyclodextrin on the complexation between MB and TSPP have been examined by means of absorption and fluorescence spectroscopy. The binding of CDs to TSPP and/or MB in the MB–TSPP complex causes the dissociation of the MB–TSPP complex.

Electronic absorption, fluorescence, and circular dichroism spectroscopic studies on the inclusion complexes of tetrakis(4-sulfonatophenyl)porphyrin with cyclodextrins in basic aqueous solutions

In aqueous solutions of pH 10.1, inclusional complexation of tetrakis(4-sulfonatophenyl)porphyrin (TSPP) with α-cyclodextrin (α-CD), β-CD, heptakis(2,3,6-tri- O-methyl)-β-CD (TM-β-CD), and γ-CD has been examined by means of absorption, fluorescence, and induced circular dichroism spectra. Upon the addition of CD to a basic solution of TSPP, its absorption peak is shifted to longer wavelengths and the fluorescence peak is slightly shifted to longer wavelengths, with a band sharpening. α-CD and β-CD most likely form 1 : 1 and 2 : 1 host–guest inclusion complexes with TSPP. TM-β-CD and γ-CD form 2 : 1 and 1 : 1 inclusion complexes with TSPP, respectively. An equilibrium constant for the formation of the 2 : 1 TM-β-CD–TSPP inclusion complex has been estimated to be 2.92 × 10 13 mol −2 dm 6 from a simulation for the absorbance change of TSPP with the TM-β-CD concentration. An equilibrium constant ( K 1) for the formation of the 1 : 1 γ-CD–TSPP inclusion complex has been evaluated to be 1800 ± 100 mol −1 dm 3 from the absorbance change. This K 1 value is nearly the same as that (1600 ± 200 mol −1 dm 3) obtained from the fluorescence intensity change, supporting the formation of the 1 : 1 γ-CD–TSPP inclusion complex. An induced circular dichroism spectrum of TSPP in the presence of α-CD or β-CD exhibits a negative sign, whereas that in the presence of TM-β-CD or γ-CD exhibits a positive sign, indicating different inclusion modes.

Singlet Oxygen Production in Water: Aggregation and Charge-Transfer Effects

Precise quantum yields for generation of singlet molecular oxygen, O2(1Δg), have been measured for tetrakis(4-sulfonatophenyl)porphyrin (TSPP), closely-related water-soluble porphyrin derivatives, and tris(2,2‘-bipyridyl)ruthenium(II) (bpy3Ru2+) in O2-saturated water. Under the experimental conditions, TSPP is present in an aggregated state, but the measured quantum yield for formation of O2(1Δg), ΦΔ = 0.51, remains on the same order as that of the corresponding monomer in methanol, ΦΔ = 0.70. Comparison with the quantum yield for formation of the triplet state indicates that quenching of the triplet by O2 gives O2(1Δg) with an efficiency of ca. 80%. There is a small but significant increase in ΦΔ when D2O is used in place of H2O. For the other porphyrin derivatives, the ability of the aggregate to sensitize formation of O2(1Δg) appears to depend on the total electronic charge resident on the molecule, decreasing with decreasing negative charge. A strong solvent dependence noted for O2(1Δg) production with (bpy3Ru2+) is explained in terms of competition between triplet energy transfer and photoinduced electron (or partial charge) transfer. Similar behavior could be responsible for the relatively low ΦΔ value observed for TSPP.

Synthesis and spectroscopy of TPP derivative-doped silica gels prepared by the sol-gel process

Tetrakis (4-sulfonatophenyl) porphyrin (TSPP) and terakis (N-methyl-4-pyridyl) porphyrin 4+ (TMPyP) which are well known as photochemical hole burning (PHB) dyes, were incorporated in silica gels obtained by the sol-gel process from tetramethoxysilane (TMOS). The hole-burning experiment was performed at 4.2 K. The hole-burning efficiency was quite lower for TSPP than for TMPyP. This result suggests the existence of PHB inactive or ineffective state for TSPP in the silica gel.