Porphyrin Absorption Research Articles

Interaction of cationic 5,10,15,20-tetra(N-methylpyridyl)porphyrin and its Co(III) complex with premicellar SDS aggregates: Structure and properties

The study explores the interactions between 5,10,15,20-tetra(N-methylpyridyl)porphyrin (H2P) and sodium dodecyl sulfate (SDS) at concentrations below the critical micelle concentration (CMC) in aqueous solutions employing spectrophotometric and fluorescence methods. The composition and structure of the complexes involved in the association of H2P with premicellar SDS aggregates of varying compositions denoted as [H2P-5·SDS], [H2P-10·SDS] and [H2P-20·SDS] were characterized using mass spectrometry, DOSY, and 1D NOESY techniques. Possible reasons for the decrease in the intensity of absorption and emission of porphyrin in micellar aggregates of SDS compared to porphyrin in an aqueous environment are analyzed.The research has revealed that SDS can act as both a catalyst and an inhibitor, depending on its concentration in the reaction of complexation of H2P with metal cations (Co2+). The spectrophotometric approach examined interaction processes between 5,10,15,20-tetra(N-methylpyridyl)porphyrinate Co(III) and premicellar SDS aggregates, which proceed similarly to the processes with the porphyrin ligand. The study demonstrated the impact of premicellar aggregates on the binding capacity of Co(III) porphyrinate with electron-donating molecules using imidazole as an illustrative example.

Localized Excitons in Zn-Porphyrin Covalently Functionalized MoS2 and WS2

We successfully functionalized MoS2 and WS2 with Zn-porphyrin through 1,2-dithiolane addition. This creates mixed 0–2 dimensional materials since porphyrins are discrete on the basal plane of TMDs. This localization results in a new emission band with a 3.5 ns lifetime at 77.5 K with an excitation power of 17 W/cm2 in the near-infrared (NIR) region (1.40–1.51 eV), which originates from charge-separated states between ZnP and WS2. The optical response of excitonic species, including trion, biexcitons, and excitons, is substantially enhanced at the porphyrin absorption region, supporting electron transfer between ZnP and WS2. Sensing time-response improves after functionalization, suggesting that electrons injected from ZnP to TMDs contribute to filling trap states. Incorporating ZnP also enhances the stability of WS2 and MoS2 against atmospheric photodegradation. Theoretical modeling supports these findings, suggesting an intimate relationship between orbitals in the ground and excited states of porphyrin and TMDs.

Solvent effects on nonlinear absorption of meso-tetrakis methylpyridiniumyl porphyrin for picosecond pulse trains

Solvent effects on nonlinear absorption of meso-tetrakis methylpyridiniumyl porphyrin for picosecond pulse trains

Tandem C-S Coupling and Debrominative Cyclization Enables an Easy Access to β-Thiazole-Fused Porphyrins.

A catalyst-free synthetic approach to β-thiazole-fused 5,10,15,20-tetraarylporphyrins via a cascade reaction of nickel(II) or copper(II) 2-amido-3-bromo-5,10,15,20-tetraarylporphyrins and Lawesson's reagent is described. During the course of the reaction, 3-bromo-2-thioamido-5,10,15,20-tetraarylporphyrins formed in situ undergo debrominative cyclization in refluxing toluene to provide novel β-thiazole-fused porphyrin macrocycles in good yields. Furthermore, free-base and zinc(II) β-thiazole-fused porphyrins have also been constructed in excellent yields by using standard demetalation and zinc metal insertion procedures. The preliminary photophysical studies revealed a significant bathochromic shift in the electronic absorption and emission spectra of new porphyrins as compared to meso-tetraarylporphyrin precursors.

Understanding structure–properties relationships of porphyrin linked to graphene oxide through π–π-stacking or covalent amide bonds

Two graphene oxide nanoassemblies using 5-(4-(aminophenyl)-10,15,20-triphenylporphyrin (TPPNH2) were fabricated by two synthetic methods: covalent (GO-CONHTPP) and noncovalent bonding. GO-CONHTPP was achieved through amide formation at the periphery of GO sheets and the hybrid material was fully characterized by FTIR, XPS, Raman spectroscopy, and SEM. Spectroscopic measurements together with theoretical calculations demonstrated that assembling TPPNH2 on the GO surface in DMF-H2O (1:2, v/v) via non-covalent interactions causes changes in the absorption spectra of porphyrin, as well as efficient quenching of its emission. Interestingly, covalent binding to GO does not affect notably neither the porphyrin absorption nor its fluorescence. Theoretical calculations indicates that close proximity and π–π-stacking of the porphyrin molecule with the GO sheet is possible only for the non-covalent functionalization. Femtosecond pump–probe experiments revealed that only the non-covalent assembly of TPPNH2 and GO enhances the efficiency of the photoinduced electron transfer from porphyrin to GO. In contrast to the non-covalent hybrid, the covalent GO-CONHTPP material can generate singlet oxygen with quantum yields efficiency (ΦΔ = 0.20) comparable to that of free TPPNH2 (ΦΔ = 0.26), indicating the possible use of covalent hybrid materials in photodynamic/photothermal therapy. The spectroscopic studies combined with detailed quantum-chemical analysis provide invaluable information that can guide the fabrication of hybrid materials with desired properties for specific applications.

Self-Assembly of Chiral Cyclohexanohemicucurbit[n]urils with Bis(Zn Porphyrin): Size, Shape, and Time-Dependent Binding.

In order to investigate the ability of bis(zinc octaethylporphyrin) (bis–ZnOEP) to discriminate cyclohexanohemicucurbit[n]urils (cycHC[n]) of different shapes and sizes, the self-assembly of barrel-shaped chiral cycHC[n] with bis–ZnOEP was studied by various spectroscopic methods (absorption, fluorescence, circular dichroism (CD), and NMR). While the binding of 6-membered cycHC[6] induced a tweezer-like conformation followed by the formation of anti-form of bis–ZnOEP upon further addition of cycHC[6], the interaction of 8-membered cycHC[8] is more complex and proceeds through the featured syn-to-anti conformational change of bis–ZnOEP and further intermolecular self-assembly via multiple noncovalent associations between cycHC[8] and bis–ZnOEP. Whilst bis–porphyrins are known to be effective chemical sensors able to differentiate various guests based on their chirality via induced CD, their ability to sense small differences in the shape and size of relatively large macrocycles, such as chiral cycHC[6] and cycHC[8], is scarcely examined. Both studied complexes exhibited characteristic induced CD signals in the region of porphyrin absorption upon complexation.

Plasmon-enhanced dye-sensitized solar cells through porphyrin-silver nanoparticle hybrid structures: Experimental and computational studies

Surface plasmon resonance of silver nanoparticles (Ag NPs) was used to improve light absorption of porphyrins in plasmon-enhanced porphyrin-sensitized solar cells (PSSCs). Porphyrins with different substituents consisting –H, -Me, -MeO, –F, -Cl, -Br, –CO2H, –SO3H, –NO2, and –NH2 were used to study the effect of the interactions between photoactive dye molecules and plasmonic Ag NPs on the performance of PSSCs. The obtained results revealed that zinc tetra(4-carboxyphenyl)porphyrin and zinc tetra(4-aminophenyl)porphyrin have made the biggest impact on the performance of plasmon-enhanced PSSCs. Computational studies were done to study the electronic properties of porphyrin molecules with electron-withdrawing and electron-donating substituents interacted with Ag NPs. The theoretical studies confirmed that the electronic nature of substituents of porphyrins has a considerable effect on the electronic properties of porphyrin-AgNPs systems. In continue, [email protected] core-shell NPs were prepared to overcome the challenge of corrosion of Ag plasmonic nanoparticles. The results showed that using [email protected] systems, in many cases, the performance of PSSCs is increased relative to corresponding porphyrins but is decreased relative to porphyrin-AgNPs systems.

The use of light in the treatment of acne vulgaris-a review.

Topical and oral antibiotic therapy is also a popular method of treatment. The effectiveness of this method is limited by the increasing resistance of bacteria to antibiotics. Over the decades since the introduction of antibiotics to treat acne, the resistance levels of bacteria have changed. This defense mechanism is developed evolutionarily. Modifications of antibiotic receptor sites, alteration of drug influx/efflux, or enzymatic degradation are common mechanisms used by bacteria to initiate and strengthen internal antibiotic resistance. The basic chromophores used in light therapy are hemoglobin, melanin, water bound to proteins, and porphyrins. Hemoglobin absorbs light mainly at 580nm, while melanin absorbs the entire visible spectral range (400-750nm). Porphyrins are aromatic compounds, classified as photosensitizing substances, intensively absorbing blue light, and to a lesser extent in long visible bands, such as orange and red light. Using IPL makes it possible to cover the maximum light absorption of porphyrins and hemoglobin, therefore it can be an effective tool in the treatment of inflammatory lesions in acne vulgaris. In view of the effectiveness of light therapy and its effect even on antibiotic-resistant bacteria, it is worth considering the possibility of using light therapy instead of antibiotic therapy. Due to the increasing resistance of bacteria to antimicrobials, they should be used with caution and as a last resort. The high-energy light treatment act only locally (unlike with antibiotics taken orally) and on a chromophore, such as melanin, hemoglobin, or porphyrins.

Aerosol-based antimicrobial photoinactivation in the lungs: an action spectrum study

Chronic lung infections are among the most diffused human infections, being often associated with multidrug-resistant bacteria. In this framework, the European project “Light4Lungs” aims at synthesizing and testing an inhalable light source to control lung infections by antimicrobial photoinactivation (aPDI), addressing endogenous photosensitizers only (porphyrins) in the representative case of S. aureus and P. aeruginosa. In the search for the best emission characteristics for the aerosolized light source, this work defines and calculates the photo-killing action spectrum for lung aPDI in the exemplary case of cystic fibrosis. This was obtained by applying a semi-theoretical modelling with Monte Carlo simulations, according to previously published methodology related to stomach infections and applied to the infected trachea, bronchi, bronchioles and alveoli. In each of these regions, the two low and high oxygen concentration cases were considered to account for the variability of in vivo conditions, together with the presence of endogenous porphyrins and other relevant absorbers/diffusers inside the illuminated biofilm/mucous layer. Furthermore, an a priori method to obtain the “best illumination wavelengths” was defined, starting from maximizing porphyrin and light absorption at any depth. The obtained action spectrum is peaked at 394 nm and mostly follows porphyrin extinction coefficient behavior. This is confirmed by the results from the best illumination wavelengths, which reinforces the robustness of our approach. These results can offer important indications for the synthesis of the aerosolized light source and definition of its most effective emission spectrum, suggesting a flexible platform to be considered in further applications.

Photostable Platinated Bacteriochlorins as Potent Photodynamic Agents.

Photodynamic therapy (PDT) is used to treat various cancerous diseases. Recently, we have demonstrated that platinated pyridyl-substituted porphyrins are potent agents for PDT with very high phototoxicity (IC50 down to 17 nM) and excellent phototoxic indices of higher than 5800 (p.i. = IC50(dark)/IC50(light)) [Rubbiani, R. et al., Chem. Commun. 2020, 56, 14373]. However, the absorption of porphyrins is not ideal for the treatment of larger tumors because they essentially do not absorb light between 650 and 850 nm. Herein, we report stable conjugates of a novel bacteriochlorin with cisplatin and transplatin. They exhibit extremely high phototoxicity (IC50 values down to 6 nM, irradiated with a 750 nm LED at a fluence of 5 J/cm2), very low dark toxicity, and thereby extremely high phototoxic indices up to 8300. Based on these exciting results, we believe that platinated bacteriochlorins are promising candidates for further investigation as novel PDT anticancer agents.

Ethyne Functionalized Meso-Phenothiazinyl-Phenyl-Porphyrins: Synthesis and Optical Properties of Free Base Versus Protonated Species.

Synthesis, structural characterization and photophysical properties for a series of new trans-A2B2- and A3B-type ethynyl functionalized meso-phenothiazinyl-phenyl porphyrin derivatives are described. The new compounds displayed the characteristic porphyrin absorption spectra slightly modified by weak auxochromic effects of the substituents and fluorescence emission in the range of 651–659 nm with 11–25% quantum yields. The changes recorded in the UV-vis absorption spectra in the presence of trifluoroacetic acid (TFA) are consistent with the protonation of the two internal nitrogen atoms of the free-base porphyrin (19 nm bathochromic shift of the strong Soret band and one long wave absorption maxima situated in the range of 665–695 nm). Protonation of the phenothiazine substituents required increased amounts of TFA and produced a distinct hypsochromic shift of the long wave absorption maxima. The density functional theory (DFT) calculations of a porphyrin dication pointed out a saddle-distorted porphyrin ring as the ground-state geometry.

Two spectral QSPR models of porphyrin macromolecules for chelating heavy metals and different ligands released from industrial solvents: CH2Cl2, CHCl3 and toluene

ABSTRACT Two simple and reliable correlations are introduced for the prediction of emission and absorption of porphyrins and their derivatives, i.e. metalloporphyrins and ligand coordinated metalloporphyrins. They can be used to sense the extracted precious metals. The proposed models require only simple structural parameters such as the number of carbon, metal and metal-free molecular fragments of desirable porphyrins or their derivatives. Since the proposed models depend on molecular structures of the desired compounds, they can be easily applied for complex molecular structures. Experimental data of 272 porphyrin derivatives were used to derive and test the novel models for the assessment of their emission (Em.) and absorption (Abs.) values in three solvents namely dichloromethane, toluene and chloroform. The values of the coefficients of determination (r 2) for the training set (183 compounds) in dichloromethane and three different test sets, corresponding to the three mentioned solvents, for the emission and absorption correlations were greater than 0.70. The calculated values of the root-mean-square error (RMSE) for the training sets of Em. and Abs. correlations were equal to 7.56 and 4.86 nm, respectively. Further statistical parameters also confirm the high reliability of the new models.

Microwave-assisted Petroporphyrin Release from Asphaltene Aggregates in Polar Solvents

This work presents an efficient approach for the primary separation of the petroporphyrin component from asphaltene aggregates. The n-pentane asphaltenes separated from the vacuum residue of Canadian oil sands bitumen were used as the feedstock. The release behavior of petroporphyrins from feed asphaltenes in polar solvents with the assistance of microwave irradiation was investigated. UV–vis spectroscopy was utilized to calculate the petroporphyrin release efficiency (PRE). The effects of asphaltene concentrations and solvent properties on the PRE were discussed. Results show that, under the microwave irradiation, asphaltenes could be rapidly separated into soluble and insoluble fractions. The solubles are enriched with vanadyl porphyrins, while the insolubles present only weak absorption of nickel porphyrins at proper asphaltene concentrations. The dispersion force (fd) of solvents has a strong correlation with the PRE. Under the optimized conditions of the methanol/toluene volume ratio of 2:1, the microwave time of 10 min, and the asphaltene concentration of 0.08 g/L, the PRE can reach up to 45%. Compared with the traditional solvent extraction method, the PRE of this new method is improved prominently. The possible mechanism of selective activation of petroporphyrin motivated by the microwave irradiation and the formation of asphaltene vesicles is proposed. This work could provide a more efficient technique to purify petroporphyrins from asphaltenes and could give insight into the interactions between petroporphyrins and asphaltene aggregates.

Ping-Pong Energy Transfer in Covalently Linked Porphyrin-MoS2 Architectures.

Molybdenum disulfide nanosheets covalently modified with porphyrin were prepared and fully characterized. Neither the porphyrin absorption nor its fluorescence was notably affected by covalent linkage to MoS2. The use of transient absorption spectroscopy showed that a complex ping‐pong energy‐transfer mechanism, namely from the porphyrin to MoS2 and back to the porphyrin, operated. This study reveals the potential of transition‐metal dichalcogenides in photosensitization processes.

Porphyrin functionalized bismuth ferrite for enhanced solar light photocatalysis.

In this work, multiferroic bismuth ferrite (BFO) was functionalized with meso-tetraphenylporphine-4,4',4'',4'''-tetracarboxylic acid (TCPP). This new hybrid organic-inorganic material shows an enhanced photocatalytic activity for the degradation of organic dyes as it combines the properties of BFO which is an efficient visible light photocatalyst with peculiar porphyrin absorption in visible light. The anchoring of TCPP to the OH-terminations of the BFO surface through its carboxylic tethering groups was demonstrated using X-ray photoelectron spectroscopy and FT-IR spectroscopy. The photocatalytic activity of the material was also demonstrated through the photocatalytic degradation of Methylene Blue (MB) and Rhodamine-B (Rhd-B) in water under simulated solar light illumination. The TCPP molecules anchored to BFO slightly decrease (∼0.06 eV) the bandgap energy of the system and act as new catalytic centres, thus improving its photocatalytic activity. A photodegradation mechanism was also proposed. This new material is reusable and stable, as it maintains an unmodified photo-activity after several MB discoloration runs.

Enhanced photocatalytic activity and photothermal effects of cu-doped metal-organic frameworks for rapid treatment of bacteria-infected wounds

Owing to the increasing drug-resistance, antibiotics-free strategy is urgent for the therapy of bacterial infections. Herein, Cu2+ is introduced into the porphyrin ring of PCN 224, which enhances the photocatalytic property of MOFs. The doped Cu2+ could trap electrons, thus suppresses electron-hole recombination and accelerates the transfer of carriers under 660 nm light irradiation, thereby enhancing the yields of reactive oxygen species (ROS). Furthermore, the Cu-MOFs’ photothermal effect is strengthened due to the d–d transition. However, overdoping of Cu2+ weakens the photocatalytic and photothermal properties due to the trapping of more photo-electrons by Cu2+ and the decreased light absorption of porphyrin at 660 nm. Doping with 10% Cu2+ endows the MOFs with the best antibacterial efficacy of 99.71% against Staphylococcus aureus within 20 min because of the synergistic effects of ROS and heat. Furthermore, the in vivo results show that Cu2+-MOFs kill bacteria efficiently, thus accelerating wound healing.

Dye-sensitized graphitic carbon nitride (g-C3N4) for photocatalysis: a brief review

Photocatalytic semiconductors by solar light have received significant attention for their application on photocatalytic H2 evolution, degradation of pollutants, CO2 reduction, and so on. Among them, graphitic carbon nitride (g-C3N4) has the properties of earth rich, metal-free, high physicochemical stability, and suitable electronic band structure and band gap for many kinds of photocatalyst reactions. However, the energy conversion efficiency still limited due to the low utilization efficiency in the longer wavelength. Dye sensitization is currently one of promising methods to extend the absorption response region of semiconductors, and enhances the separation and transportation of photogenerated electrons and holes between dyes and semiconductors. It may be a good candidate strategy to enhance photocatalysis efficiency, even though lack of stability and repeatability for these composites. In this article, we have summarized dye-sensitized g-C3N4 with different mechanisms for variety of photocatalysis process, the relationship between structure of dyes and photocatalytic activity. Especially, dyes in H2 evolution process are divided into metal-free organic dyes, phthalocyanines, and porphyrins in detail. Comparing to metal-free organic dyes, the absorption of phthalocyanines and porphyrins can easily move to near-infrared region, which lead to the enhancement of H2 evolution activity. It may provide a guidance of the structure designing and constructing for highly effective dye-sensitized g-C3N4 photocatalysts for various applications. At last, we shared our opinions on the challenges and perspectives of dyes on g-C3N4 for photocatalyst.

(Aminophenyl)porphyrins as precursors for the synthesis of porphyrin-modified siloxanes

The present research reports the efficient synthesis of mono- and di-(aminophenyl)porphyrins and their metalation with Zn(II) using microwave irradiation. The subsequent reaction of amino-functionalized porphyrins with siloxane moieties bearing epoxy or carboxyl functional groups provided four new porphyrin-modified siloxanes. The structure of the resulting derivatives was established by 1H-NMR and MALDI-TOF-MS. The optical properties of the porphyrin chromophores were preserved, as proven by comparing the absorption and emission spectra of the initial porphyrins to those of the porphyrin-modified siloxanes.

Synthesis, Structures, and Near-IR Absorption of Heterole-Fused Earring Porphyrins.

A reaction sequence of regioselective peripheral bromination, Suzuki-Miyaura coupling with 2-borylated thiophene or pyrrole, and oxidative ring-closure with FeCl3 allowed the synthesis of heterole-fused earring porphyrins 4Pd and 9Pd from the parent earring porphyrin 1. Differently pyrrole-fused porphyrins 5H and 6H and their PdII complexes 5Pd and 6Pd were also synthesized. The structures of 4Pd, 5H, 6Pd, and 8Pd have been revealed by X-ray analysis to be slightly twisted owing to constraints imposed by heterole-fused structures. 5Pd exhibits an intensified band at 1505 nm, while 4Pd and 9Pd display small but remarkably red-shifted absorption bands reaching around 2200 nm.

Universality of Ethane-Bridged Bis-Porphyrin Structural Motiff for Chirality and Molecular Sensing

Covalently linked porphyrins are of particular interest for the scientific community as efficient artificial systems widely used in various practical applications in the numerous research and technoligical fields such as polymer and nano science, light harvesting and nonlinear optics, different sensors and catalysis, molecular and chiral recognition, various supramolecular and chiroptical devices, chirogenesis and absolute configuration determination. Recently, we have found that a simple ethane-bridged bis-porphyrin structural motif, 1 (M = Zn, Mg, Cu, Co, 2H), can be effectively served for various application purposes owing to the specific molecular and supramolecular functionalities. In particular, the unique functional property of this bis-porphyrin host is based upon the structural semi-flexibility of covalent linkage between two porphyrin units resulting in the environmentally assisted syn-anti conformational switching and tweezer formation depending upon the guest structure, which can be effectively employed in different sensing areas.1-11 For example, in the case of monodentate chiral guests there is the unidirectional screw formation in the anti form of 1 (M = Zn, Mg, 2H) upon the corresponding host-guest interaction. The direction of screw governs by the size difference of ligand’s substituents at the chirogenic center resulting in chirality transfer to the bis-porphyrin host and induction of the noticeable exciton couplet CD signals in the porphyrin absorption region.1-6 This chirogenic phenomenon was efficiently utilized for determining the absolute configuration of various chiral guests, thus making it possible to apply 1 as effective and universal chirality sensors for different types of organic molecules as in solution and in solid state. To expand further the applicability of these supramolecular systems Langmuir–Schaefer (LS) thin-films on the basis of 1 have been prepared and employed as highly selective and sensitive sensors for aromatic amines.7-9 For example, the monometallated Cu complex of 1 is able to detect the presence of aniline in aqueous solution at a concentration as low as 1 nM.9 The sensory mechanism includes the corresponding host-guest interaction resulting in the syn-to-anti conformational switching, which can be easily detected by various spectroscopic methods. Another sensing application of the LS film of monometallated Co complex of 1was found in the field of detection of volatile organic compounds like alcohol vapors and oxidizing gas as NO2 by using magneto-optical surface plazmon resonance spectroscopy.10 The detection mechanism is based upon the molecular recognition correlating with the alcohol molecular structure. More simple sensing system was developed on the basis of spin-coated thin films of the monometallated Zn complex of 1.11 The obtained thin films were successfully employed to detect ammonia and acetone as the relevant analytes in aqueous solutions. This was a result of the supramolecular interaction between each of these two compounds and the bis-porphyrin active layer, inducing the corresponding tweezer conformation easily detectable by UV–vis absorption spectroscopy in the range of concentrations between 1 ppm and 20 ppm for both the analytes. Further developments and prospects toward new sensing systems on the basis of heterometallic bis- and multi-porphyrin structures will be discussed. Borovkov, Symmetry 2014, 6, 256.Borovkov, Symmetry 2010, 2, 184.Borovkov, Y. Inoue, Eur. J. Org. Chem. 2009, 189.A. Hembury, V. V. Borovkov, Y. Inoue, Chem. Rev. 2008, 108, 1.V. Borovkov, Y. Inoue, Top. Curr. Chem. 2006, 265, 89.V. Borovkov, G. A. Hembury, Y. Inoue, Acc. Chem. Res. 2004, 37, 449.Giancane, V. Borovkov, Y. Inoue, L. Valli, J. Colloid Interface Sci. 2012, 385, 282.Giancane, V. Borovkov, Y. Inoue, S. Conoci, L. Valli, Soft Matter 2013, 9, 2302. Bettini, E. Maglie, R. Pagano, V. Borovkov, Y. Inoue, L. Valli, G. Giancane, Beilstein J. Nanotechnol. 2015, 6, 2154.Colombelli, M.G. Manera, V. Borovkov, G. Giancane, L. Valli, R. Rella, Sensor Actuat. B-Chem., 2017, 246, 1039.A. Buccolieri, D. Manno, A. Serra, A. Santino, M. Hasan, V. Borovkov, G. Giancane, Sensor Actuat. B-Chem., 2018, 257, 685.