Soret Band Research Articles

Ultrafast Dynamics and Strong Two-Photon Absorption Properties of Nonplanar β-Functionalized “Push–Pull” Copper Corroles with a Mixed Substituent Pattern

A new series of nonplanar and unsymmetrically β-functionalized "push-pull" copper corroles, CuTPC(CHO)R7 [R = H, Br, Ph, Me, or 2-thienyl (Th)], were synthesized and characterized to elucidate the effect of β-functionalization and nonplanarity on the photophysical, redox, and nonlinear optical (NLO) properties on the corrole ring. The synthetic route to unsymmetrically β-octasubstituted copper corroles includes bromination of CuTPC(CHO) to get CuTPC(CHO)Br7 in 80% yield, which was further subjected to the Pd-catalyzed Suzuki reaction. CuTPC(CHO)Br7 exhibited a large red shift in the Soret band (Δλmax = 35-40 nm) and both the Q bands (Δλmax = 10-50 nm), as compared to CuTPC and CuTPC(CHO). CuTPC(CHO)Br7 was 510 and 290 mV anodically shifted in the first oxidation and the first reduction compared to CuTPC owing to the strong -I effect of CHO and Br groups. Density functional theory studies revealed that all the β-octasubstituted copper corroles exhibited highly nonplanar saddle-shape conformation of the corrole ring. Very high torsional saddling was observed for CuTPC(CHO)Th7 (79-83°) than that for CuTPC (49-53°), even larger than that for CuTPCBr8 (67-70°). Femtosecond laser-induced third-order NLO studies from these copper corroles showed strong two-photon absorption cross-sections (0.48-6.98 × 104 GM) and self-focusing-type positive nonlinear refraction behavior. The observed structure-dependent two-photon absorption coefficients (β) are in the range of ∼2.7-20.9 × 10-12 m/W, and the n2 values are in the range of ∼0.64-6.45 × 10-18 m2/W. The present results may facilitate a new window for these copper corroles in nonlinear optical devices, femtosecond optical limiters, and many other ultrafast photonic applications.

Ruffle-distorted meso-silylethynyl-substituted naphthoporphyrin showing near-infrared Q band beyond 800 nm

Designing stable molecules with near-infrared (NIR) absorption and good light-to-heat conversion performance is important for phototherapy applications. Herein, we report the synthesis of copper-coordinated meso-tetrakis(triisopropylsilylethynyl)-tetranaphthoporphyrin 2-Cu by retro-Diels Alder reaction, which exhibited a Soret band at 534 nm and a NIR Q band at 818 nm. The single-crystal X-ray analysis of 2-Cu revealed a purely ruffle-distorted conformation with an S4 symmetry axis. Theoretical calculations show that 2-Cu has a narrower HOMO-LUMO gap than its meso-phenyl and meso-free analogs due to a decrease in LUMO energy level. The photothermal investigation of 2-Cu under 808 nm laser irradiation demonstrated its outstanding photostability and high photothermal conversion efficiency, indicating its promise as a photothermal therapeutic agent after functionalization.

Porphyrin Polymers Bearing N,N'-Ethylene Crosslinkers as Photosensitizers against Bacteria.

The appearance of microbes resistant to antibiotics requires the development of alternative therapies for the treatment of infectious diseases. In this work two polymers, PTPPF16-EDA and PZnTPPF16-EDA, were synthesized by the nucleophilic aromatic substitution of 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin and its Zn(II) complex with ethylenediamine, respectively. In these structures, the tetrapyrrolic macrocycles were N,N'-ethylene crosslinked, which gives them greater mobility. The absorption spectra of the polymers showed a bathochromic shift of the Soret band of ~10 nm with respect to the monomers. This effect was also found in the red fluorescence emission peaks. Furthermore, both polymeric materials produced singlet molecular oxygen with high quantum yields. In addition, they were capable of generating superoxide anion radicals. Photodynamic inactivation sensitized by these polymers was tested in Staphylococcus aureus and Escherichia coli bacteria. A decrease in cell viability greater than 7 log (99.9999%) was observed in S. aureus incubated with 0.5 μM photosensitizer upon 30 min of irradiation. Under these conditions, a low inactivation of E. coli (0.5 log) was found. However, when the cells were treated with KI, the elimination of the Gram-negative bacteria was achieved. Therefore, these polymeric structures are interesting antimicrobial photosensitizing materials for the inactivation of pathogens.

Synthesis of Red-Light-Responsive Pheophorbide-a Tryptamine Conjugated Photosensitizers for Photodynamic Therapy.

Six methyl pheophorbide-a derivatives were prepared by linking a tryptamine side chain at the C-131 , C-152 and C-173 positions of pheophorbide-a. Prepared conjugates were characterized and evaluated for their photocytotoxicity against A549 cells. The conjugate 6 a with strong absorption at 413 nm (Soret band), 663-671 nm (Q bands) and comparable fluorescence quantum yield (0.26) was found to exhibit significant cytotoxicity (659 nM). Molecular integration of pheophorbide-a and tryptamines showed synergistic effects as the most potent conjugate 6 a was identified with enhanced photocytotoxicity when compared to methyl pheophorbide-a. The conjugate 6 a was smoothly taken up by A549 cells and exhibited intracellular localization predominantly to lysosome in the cytoplasm. Upon photoirradiation 6 a generated singlet oxygen to show potent cytotoxicity toward A549 cells.

DMAP and HMTA manganese(III) meso-tetraphenylporphyrin-based coordination complexes: Syntheses, physicochemical properties, structural and biological activities

The reactions of the (triflato)(meso-tetra(para-methoxyphenyl)porphyrinato)manganese(III) ([MnIII(TMPP)(SO3CF3)] complex with an excess of 4-dimethylaminopyridine (DMAP) and hexamethylenetetramine (HMTA) have been examined. These reactions yield crystalline [MnIII(TMPP)(DMAP)2](0.1Cl)(0.9SO3CF3)•2CHCl3 (I) and [MnIII(TMPP)(HMTA)2](SO3CF3)•2CH2Cl2 (II) complexes, respectively. The hyper d-type electronic spectra of I-II are characteristic for high-spin (S = 2) Mn(III) metalloporphyrins with very redshifted Soret bands. A cyclic voltammetry investigation was carried out on these two Mn(III) coordination compounds. The crystal structures of the solid complexes I-II were determined by X-ray single-crystal diffraction and elucidated by Hirshfeld surface approach. Furthermore, bioactivity of the H2TMPP free base, the [MnIII(TMPP)(SO3CF3)] starting material and complexes I-II, was assessed by a set of in vitro tests checking for antioxidant, antibacterial and antifungal (against several strains) effects.

Polariton Formation from Soret Band Excitons in Metal–Organic Frameworks and Plasmonic Lattices

Polariton Formation from Soret Band Excitons in Metal–Organic Frameworks and Plasmonic Lattices

A2B2 type porphyrins with meso-donor groups: Synthesis, X-ray structures, DFT studies and photocatalytic application using sunlight

The trans-A2B2 type porphyrins bearing thiophene linked N-butylcarbazole or N-butylphenothiazine groups at the meso-positions were synthesized. Donor−acceptor (D−A) type meso-substituted porphyrins and their Zn(II) and Pd(II) complexes were studied by UV–vis absorption, fluorescence and electrochemical techniques. These porphyrins exhibited efficient energy transfer (∼78%) from the meso-donors (thiophene linked N-butylcarbazole or N-butylphenothiazine groups) to the porphyrin core. Also, the Soret band of porphyrins was noticeably broad, indicating significant communication between the meso-donor groups and the porphyrin core. The donor−acceptor interaction between the porphyrin core and the meso-donors was supported by X-ray analysis and DFT studies of these D-A systems. The photo-catalytic application of Pd(II) porphyrin was demonstrated by efficient singlet oxygen generation (68%) and effective oxidation of aromatic aldehydes to their corresponding carboxylic acids (up to 99%) in the presence of white light or sunlight.

Decrypting the Influence of Axial Coordination on the Electronic Microenvironment of Co-N 5 Site for Enhanced Electrocatalytic Reaction

Decrypting the Influence of Axial Coordination on the Electronic Microenvironment of Co-N ₅ Site for Enhanced Electrocatalytic Reaction

STUDY ON THE ANTIBACTERIAL ABILITY OF THE HYBRID MATERIAL BETWEEN PORPHYRIN AND NANO SILVER

Water-soluble porphyrins di(4-aminophenyl)-di(4-sulfophenyl)- diphenyl-porphyrin [(SO3)2-TPP-(NH2)2](TASP) and nano-silver materials (AgNPs) were successfully synthesized by chemical synthesis and green synthesis from guava leaf extracts, respectively. The silver nanoparticle size is well controlled in the range of 1.1 - 1.5 nm. Then, AgNPs\TASP hybrid materials were successfully synthesized by different mixing methods. The UV-Vis spectrum of the hybrid material depends on the AgNPs:TASP mixing ratio and still shows the Soret peaks and Q-bands characteristic of the porphyrin family and the broad absorption range from 300 - 600 nm of the silver nanoparticles initial. The results of an antibacterial test against both gram-negative and gram-positive strains on LB agar showed that all samples had different antibacterial activities. In which, the AgNPs\TASP hybrid material has better inactivation ability than silver nano for both tested bacterial strains. Besides, the presence of polypyrrole conducting polymer (PPy) has promoted the kinetics of silver ion release, which also gives outstanding antibacterial results, thereby opening the potential to fabricate hybrid materials for antibacterial applications.

Electropolymerization of Metallo-Octaethylporphyrins: A Study to Explore Their Sensing Capabilities.

The electropolymerization of metallo-octaethylporphyrins (OEP) containing copper, zinc or nickel metal were performed using cyclic voltammetry at three different potential ranges. The electropolymerized porphyrins were characterized by UV-Vis and Raman spectroscopies and the Soret band (393–445 nm) and Raman bands were used to assess the degree of electropolymerization obtained. The application for an analytical use of the modified electrodes to determine phenobarbital in aqueous solution was evaluated. The electropolymerized CuOEP produced at potentials ranging from 0.0 to 2.2 V was the best performer with a limit of detection (LoD) of 10 mg L−1 (43.07 µM), a linear range of 10–150 mg L−1 (43.07 to 646 µM), an average precision of 4.3% (%RSD) and an average % recovery of 101.34%. These results indicate that the CuOEP-modified electrode is suitable for the analysis of phenobarbital in human samples, as the concentration range varies from 10 to 40 mg L−1 (43.07 to 172.27 µM), typically found in antiepileptic treatments, to those at the toxic level (172–258 µM) or lethal levels (345–650 µM).

Carotenoid responds to excess energy dissipation in the LH2 complex from Rhodoblastus acidophilus.

The functions of both (bacterio) chlorophylls and carotenoids in light-harvesting complexes have been extensively studied during thepast decade, yet, the involvement of BChl a high-energy Soret band in the cascade of light-harvesting processes still remainsa relatively unexplored topic. Here, we present transient absorption data recorded after excitation of the Soret band in the LH2 complex from Rhodoblastus acidophilus. Comparison of obtained data to those recorded after excitation of rhodopin glucoside and B800 BChl a suggests that no Soret-to-Car energy transfer pathway is active in LH2 complex. Furthermore, a spectrally rich pattern observed in the spectral region of rhodopin glucoside ground state bleaching (420-550nm) has been assigned toanelectrochromic shift. The results of global fitting analysis demonstrate two more features. A 6ps component obtained exclusively after excitation of the Soret band has been assigned to the response of rhodopin glucoside to excess energy dissipation in LH2. Another time component, ~ 450ps, appearing independently of theexcitation wavelength was assigned to BChla-to-Car triplet-triplet transfer. Presented data demonstrate several new features of LH2 complex and its behavior following the excitation of the Soret band.

Synthesis, Structure and Studies of Meso-Triaryl 22-Oxabenzonorroles.

The first examples of meso-triaryl 22-oxabenzonorroles were synthesized in 18-21% yields by oxidation of appropriate meso-triaryl oxabenzobilane. The key precursors, the meso-triaryl oxabenzobilanes were synthesized readily by treating 16-oxatripyrrane with (1H-indol-3-yl)(p-tolyl)methanol under acid catalyzed conditions. The meso-triaryl 22-oxabenzonorroles were obtained in free base form by following our simple straight-forward synthetic strategy. The X-ray structure obtained for meso-tritolyl 22-oxabenzonorroles revealed that the indole ring was deviated by an angle of 41.27° from the mean plane. The NMR studies supported the presence of diatropic ring current effect as inner NH and CH protons were observed in the upfield region. The absorption spectra of 22-oxabenzonorroles exhibited one strong Soret band and four weak Q-bands. The electrochemical studies revealed that the macrocycles are electron rich and undergo easier oxidations. The DFT and TD-DFT studies were in agreement with the experimental observations and NICS and HOMA values supports the aromatic nature of meso-triaryl oxabenzonorroles.

Metal Sensing by a Glycine-Histidine Repeat Sequence Regulates the Heme Degradation Activity of PM0042 from Pasteurella multocida.

PM0042 protein from the Gram-negative bacterial pathogen Pasteurella multocida is homologous to the heme-degrading enzyme HutZ belonging to the pyridoxine-5-phosphate oxidase-like family. A characteristic feature of PM0042 is possession of a glycine-histidine (GH) repeat sequence at the C-terminal region. In this study, we examined the heme degradation ability of PM0042, with a particular focus on the role of the GH repeat sequence. PM0042 was expressed in Escherichia coli and successfully purified using a nickel (Ni2+)-affinity column without a histidine tag, suggesting that its GH motif facilitates binding to Ni2+. Reaction with ascorbic acid induced a significant decrease in the Soret band, suggesting the breakage of heme. While a Fe2+-ferrozine complex was not formed upon addition of ferrozine to the solution after the reaction, prior addition of metal ions to fill the metal binding site in the GH repeat sequence led to increased complex formation. In the presence of Fe2+, the heme degradation rate was accelerated ∼threefold, supporting the theory that Fe2+ binds the PM0042 protein (possibly at the GH repeat sequence) and enhances its heme degradation activity. In contrast to HutZ from Vibrio cholerae in which enzymatic activity is regulated by the protonation status of the heme proximal ligand, heme reduction is not the rate-determining step for PM0042. Rather, proton transfer to reduced oxyheme is affected, as established with the H2O/D2O isotope experiment. Based on the collective findings, the GH repeat sequence of PM0042 is proposed to function as a metal sensor that modulates iron uptake via the heme-degrading process in P. multocida.

Vacatadithiasapphyrins: Synthesis, Structure, and Spectral and Redox Properties.

Four examples of novel aromatic [22]vacatadithiasapphyrins were synthesized by refluxing appropriate [22]telluradithiasapphyrins in 1,2-dichlorobenzene in the presence of excess HCl followed by simple column chromatographic purification. The [22]vacatadithiasapphyrins can exist in three conformers "in", "out", and "zigzag" w.r.t the butadiene moiety, and under our experimental conditions, the "out" conformer was the major compound. The X-ray structure obtained for one of the "out" conformers of vacatadithiasapphyrins revealed that the macrocycle was planar similar to its parent telluradithiasapphyrin and showed effective π-delocalization over the entire macrocyclic core. NMR studies supported the formation of the "out" conformer and suggested that the vacatadithiasapphyrins were less aromatic than the parent telluradithiasapphyrins. Density functional theory, time-dependent DFT, and nuclear independent chemical shift studies indicated that the protonated form of vacatadithiasapphyrin was more aromatic than the parent protonated telluradithiasapphyrin. The absorption spectra of vacatadithiasapphyrins showed a typical strong Soret band at ∼488 nm and four relatively broad Q-bands in the region of 590-860 nm, and electrochemical studies suggest that vacatadithiasapphyrins were easier to oxidize and easier to reduce compared to the parent telluradithiasapphyrins.

The effect of radio frequency heating on the inactivation and structure of horseradish peroxidase

The effects of radio frequency (RF) heating on horseradish peroxidase (HRP) activity and its structure were investigated in this paper. The HRP was heated to 50 °C, 70 °C and 90 °C at different electrode gaps (100, 110 and 120 mm). The relative enzyme activity was 105.33 %–113.73 % at 50 °C, 91.11 %–93.05 % at 70 °C and 47.05 %–68.17 % at 90 °C. Ultraviolet–visible, circular dichroism and fluorescence spectra were used to monitor the variation in secondary and tertiary structure. The results showed that RF heating at the electrode gaps of 120 mm contributed to more severe enzyme inactivation and conformational destruction, which can be explained by the changes in Soret band, secondary structure content and tryptophan fluorescence intensity. This study revealed that enzyme inactivation by RF heating was associated with loss of helical structure, unfolding of enzyme protein and ejection of heme group.

Unique magnesium porphyrinate structure: Synthesis, characterization, and theoretical study

A new pyrazine coordinated magnesium porphyrin, [MgTClPP(pyz)2], (TClPP = meso-tetra(4-chlorophenyl)porphyrin) was synthesized and characterized using different spectroscopic techniques. A single-crystal X-ray diffraction study shows a unique magnesium porphyrinate structure with the formation of a 1D polymeric chain due to the presence of two moieties [MgTClPP(pyz)2] and [MgTClPP(H2O)2]. The plane of one porphyrin moiety is perpendicular to the plane of the other porphyrin moiety resulting in H-bonding interactions between axial ligand pyrazine of one magnesium porphyrin and water (H2O) molecule of another adjacent magnesium porphyrin. This weak intermolecular H-bonding is present between the axial ligands [-OH….N] influencing to stabilize of the polymeric chain. UV–vis spectrum of the compound shows redshift of Soret band and Q-bands on axial ligand binding. Theoretical analysis like optimization of the geometry, calculation of single-point energy, natural bond analysis, and simulation of infrared spectra was carried out using the DFT (Density Functional Theory) method. Short-range interactions such as H-bonding are quantified by the Hirshfeld surface analysis and 2D fingerprint plots. This work suggests the role of non-covalent interactions in the case of stability of coordination compounds of bridging ligands when coordinates through only one donor atom.

Interaction of the insecticide bioallethrin with human hemoglobin: biophysical, in silico and enzymatic studies

Bioallethrin is an insecticide that is widely used in households resulting in human exposure. Bioallethrin is cytotoxic to human erythrocytes. Here we have studied the interaction of bioallethrin with human hemoglobin (Hb) using in silico and biophysical approaches. Incubation of Hb (5 μM) with bioallethrin (1–50 µM) led to increase in absorbance at 280 nm while the Soret band at 406 nm was slightly reduced. The intrinsic fluorescence of Hb was enhanced with the appearance of a new peak around 305 nm. Synchronous fluorescence showed that the binding of bioallethrin to Hb mainly affects the tyrosine microenvironment. The structural changes in Hb were confirmed with a significant shift in CD spectra and about 25% loss of α-helix. Molecular docking and visualisation through Discovery studio confirmed the formation of Hb-bioallethrin complex with a binding energy of –7.3 kcal/mol. Molecular simulation showed the stability and energy dynamics of the binding reaction between bioallethrin and Hb. The structural changes induced by bioallethrin led to inhibition of the esterase activity of Hb. In conclusion, this study shows that bioallethrin forms a stable complex with human Hb which may lead to loss of Hb function in the body. Communicated by Ramaswamy H. Sarma

Synthesis, Characterization, and the N Atom Transfer Reactivity of a Nitridochromium(V) Complex Stabilized by a Corrolato Ligand.

Metal complexes bearing nitrido ligands (M≡N) are at the forefront of current scientific research due to their resemblances with the metal complexes involved in the nitrogen fixation reactions. An oxo(corrolato)chromium(V) complex was used as a precursor complex for the facile synthesis of a new nitrido(corrolato)chromium(V) complex. The nitrido(corrolato)chromium(V) complex was characterized by various spectroscopic techniques. Density functional theory (DFT) calculations were performed on the nitrido(corrolato)chromium(V) complex to assign the vibrational and electronic transitions of this complex. The chromium–nitrogen (nitrido) bond distance obtained in the DFT-optimized structure is 1.530 Å and matches well with the earlier reported authentic Cr≡N bond distances obtained from the single-crystal X-ray diffraction data. This nitrido(corrolato)chromium(V) compound exhibited a sharp Soret band at 438 nm and a Q band at 608 nm. DFT calculations deliver that the origin of the bands at 438 and 608 nm is due to the intraligand charge transfer transitions. The nitrido(corrolato)chromium(V) complex showed one reversible oxidation and one reversible reduction couple at +0.53 and −0.06 V, respectively, vs the Ag/AgCl reference electrode. The simulation of the electron paramagnetic resonance data of the nitrido(corrolato)chromium(V) compound provided the following parameters: giso = 1.987, A53Cr = 26 G, and A14N = 2.71 G. From all these analyses, we can conclude that the electronic configuration in the native state of nitrido(corrolato)chromium(V) can be best described as [(cor3–)CrV(N3–)]−. Reactions of nitrido(corrolato)chromium(V) with the chloro(porphyrinato)chromium(III) complex resulted in a complete intermetal N atom transfer reaction between chromium corrole and chromium porphyrin complexes. A second-order rate constant of 4.29 ± 0.10 M–1 s–1 was obtained for this reaction. It was also proposed that this reaction proceeds via a bimetallic μ-nitrido intermediate.

Radiodynamic therapy with CsI(na)@MgO nanoparticles and 5-aminolevulinic acid

BackgroundRadiodynamic therapy (RDT) holds the potential to overcome the shallow tissue penetration issue associated with conventional photodynamic therapy (PDT). To this end, complex and sometimes toxic scintillator–photosensitizer nanoconjugates are often used, posing barriers for large-scale manufacturing and regulatory approval.MethodsHerein, we report a streamlined RDT strategy based on CsI(Na)@MgO nanoparticles and 5-aminolevulinic acid (5-ALA). 5-ALA is a clinically approved photosensitizer, converted to protoporphyrin IX (PpIX) in cancer cells’ mitochondria. CsI(Na)@MgO nanoparticles produce strong ~ 410 nm X-ray luminescence, which matches the Soret band of PpIX. We hypothesize that the CsI(Na)@MgO-and-5-ALA combination can mediate RDT wherein mitochondria-targeted PDT synergizes with DNA-targeted irradiation for efficient cancer cell killing. Because scintillator nanoparticles and photosensitizer are administered separately, the approach forgoes issues such as self-quenching or uncontrolled release of photosensitizers.ResultsWhen tested in vitro with 4T1 cells, the CsI(Na)@MgO and 5-ALA combination elevated radiation-induced reactive oxygen species (ROS), enhancing damages to mitochondria, DNA, and lipids, eventually reducing cell proliferation and clonogenicity. When tested in vivo in 4T1 models, RDT with the CsI(Na)@MgO and 5-ALA combination significantly improved tumor suppression and animal survival relative to radiation therapy (RT) alone. After treatment, the scintillator nanoparticles, made of low-toxic alkali and halide elements, were efficiently excreted, causing no detectable harm to the hosts.ConclusionsOur studies show that separately administering CsI(Na)@MgO nanoparticles and 5-ALA represents a safe and streamlined RDT approach with potential in clinical translation.Graphical

Spectral characterization of the main pigments in the plant photosynthetic apparatus by theory and experiment

Comprehensive experimental spectroscopic and TD-CAM-B3LYP/6-31G*, DFT/MRCI libraries of the most relevant plant light harnessing pigments are presented. Included are β-carotene, zeaxanthin, violaxanthin, lutein, neoxanthin, chlorophyll a and chlorophyll b . We employ vibrational broadening with various approximations to enable direct comparison of computational to experimental data. Spectroscopic shifts based on continuum solvents and protein matrices were computed as well, employing CPCM or (for chlorophylls) QM/MM models. We also provide insight into the transient behavior after photoexcitation through optimization of the corresponding excited states. It is found, that the investigated carotenoids only differ in their excitation energies but display analogous subsequent photophysics. Vibrational broadening of the carotenoid spectra compares well to experimental data regardless of the actual approach chosen. This appears to be a result of a strong gradient at the Franck-Condon point. Thus, it is not trivial to assess which computational method is actually suited for these purposes. Further, Q and Soret band reorganization energies are very similar in both, chlorophylls a and b . Both, TD-DFT, as well as DFT/MRCI predict the existence of an intramolecular charge transfer state in the Soret region of chlorophylls. The existence/absence of this state has previously not been experimentally corroborated. However, measurements of chlorophyll a absorption spectra in different solvents support this assumption. The results suggest, that the relaxation of the chlorophyll Soret bands might be affected by the presence of such an intramolecular charge transfer state.