The photophysical, photobiological, and DNA/HSA-binding properties of corroles containing carbazole and phenothiazine moieties.

This study characterized four corrole derivatives, namely Cbz-Cor, MetCbz-Cor, PTz-Cor, and PTzEt-Cor, examining their photophysical, electrochemical, photobiological, and biomolecule-binding properties. Experimental photophysical data of absorption and emission elements correlated with a theoretical analysis obtained through time-dependent density functional theory (TD-DFT). As for the photophysical properties, we observed lower fluorescence quantum yields and discernible differences between the excited and ground states, as indicated by Stokes shift values. Natural Transition Orbit (NTO) plots presented high occupied molecular orbital - low unoccupied molecular orbital (HOMO-LUMO) densities around the tetrapyrrolic macrocycle in all examples. Our findings demonstrate that corroles maintain stability in solution and offer photostability (<20 %), predominantly in DMSO(5 %)/Tris-HCl (pH 7.4) buffer solution. Furthermore, the singlet oxygen (1O2) quantum yield and log POW values underscore their potential application in photoinactivation approaches, as these corroles serve as effective ROS generators with more lipophilic features. We also evaluated their biomolecular binding capacity towards salmon sperm DNA and human serum albumin using spectroscopic techniques and molecular docking analysis for sustenance. Concerning biomolecule interaction profiles, the corrole derivatives showed a propensity for interacting in the minor grooves of the double helix DNA due to secondary forces, which were more pronounced in site III of the human serum protein.

Studying the first order hyperpolarizability spectra in chalcone-based derivatives and the relation with one- and two-photon absorption transitions.

The first-order molecular hyperpolarizability (ß) dispersion was measured in seven chalcone-based molecules utilizing the tunable femtosecond hyper-Rayleigh scattering (tHRS) technique. Additionally, a theoretical model based on photophysical parameters was employed to better understand ß dispersion. Due to the distinct substitution patterns of the aryl/heteroaryl rings within the chalcone structure, varying profiles of one- and two-photon absorption spectra and ß dispersion were observed. The applied model highlighted two important factors contributing to achieving high ß values: (i) the presence of red-shifted one-photon and two-photon absorption bands; and (ii) the number of discernible absorption bands. To contextualize these results with other molecular structures, we employed the HRS figure of merit (FOM). Remarkably, it was revealed that chemically engineered small chalcone molecules exhibit a FOM comparable to larger quadrupolar and octupolar ones. This underscores the significance of tHRS scattering measurements and their correlation with absorptive parameters in the design and characterization of nonlinear optical materials.

Observation of the two-photon transition enhanced first hyperpolarizability spectra in cinnamaldehyde derivatives: A femtosecond regime study.

The application of nonlinear optical effects in optoelectronic devices is still scarce because the irradiance threshold necessary to induce a specific effect is very high. In this context, knowing the frequency-resolved first order molecular hyperpolarizability (ß) is essential to identifying regions where this response is intense enough to allow for applications in commercial devices. Thus, herein, we have determined the ß spectral dependence of five new push-pull cinnamylidene acetophenone derivatives using femtosecond laser-induced Hyper-Rayleigh Scattering (HRS). A considerable increase in ß values was observed in molecules. We found remarkable ß values in regions near the two-photon resonance, which are mediated by electron withdrawing and donating groups. This effect was mapped using wavelength-tunable femtosecond Z-scan technique. Furthermore, it was modeled in light of the sum-over-states approach for the second- and third-order nonlinearities. Finally, our outcomes suggest a strategy to obtain large ß values mediated by the 2PA transition.

Two-Photon Absorption and Multiphoton Excited Fluorescence of Acetamide-Chalcone Derivatives: The Role of Dimethylamine Group on the Nonlinear Optical and Photophysical Properties.

This work studied the effect of different electron-withdrawing and electron-donating groups on the linear and nonlinear optical properties of acetamide-chalcone derivatives. The results showed that the addition of the dimethylamine group led to a large fluorescence emission (71% of fluorescence quantum yield in DMSO solution) that can be triggered by two and three-photon excitations, which is essential for biological applications. Furthermore, dimethylamine also red-shifts the lower energy state by approximately 90 nm, increasing the two-photon absorption cross-section of the lower energy band by more than 100% compared with the other studied compounds. All compounds presented two-electronic states observed through one and two-photon absorption spectroscopy and confirmed by Quantum Chemistry Calculations (QCCs). QCC results were also used to model the experimental two-photon absorption cross-sectional spectrum by the Sum-Over-States (SOS) approach, revealing a dependence between the coupling of the ground state with the first excited state and the transition dipole moment between these states.

Photophysical, photobiological, and biomolecule-binding properties of new tri-cationic meso-tri(2-thienyl)corroles with Pt(II) and Pd(II) polypyridyl derivatives.

We report the synthesis and characterization of new tri-cationic corrole derivatives, containing Pt(II) or Pd(II) complexes attached at the peripheral position of thienyl moieties. Corrole derivatives were characterized through microanalysis, electrochemical, spectrometry and spectroscopy analysis. Singlet and triplet excited-states are investigated by photophysical/theoretical calculation methods and photobiological parameters were also evaluated spectroscopic techniques (UV-Vis and EPR). Also, the binding capacity of each corrole derivative with nucleic acids (DNA) and human serum albumin (HSA) was determined by UV-Vis, steady-state, and time-resolved fluorescence spectroscopy, combined with molecular docking analysis. Moreover, the new corroles containing peripheral complexes improve their interactions with biomacromolecules, generate reactive oxygen species under light source irradiation studied and has potential for application in photodynamic therapeutic processes.

Unveiling the molecular structure and two-photon absorption properties relationship of branched oligofluorenes.

Organic molecules have been intensively studied during the last few decades because of their photonics and biological applications. In this material class, the fluorene molecules present outstanding optical features, for example, high values of two-photon absorption (2PA) cross-sections, visible transparency, and high fluorescence quantum yield. Also, it is possible to improve the nonlinear optical response by modifying the fluorene molecular structure. In this context, herein, we have synthesized V and Y-shaped branching oligofluorenes containing two and three fluorene moieties in each branch. Such a molecular strategy may exponentially enhance the nonlinear optical response due to the coherent coupling among the molecular arms. Thus, we combined the use of femtosecond Z-scan spectroscopy and white light transient absorption spectroscopy (TAS) to understand the molecular structure and 2PA property relationship of branching oligofluorenes. The results show that there is a universal relationship between the 2PA cross-section and the effective π-electron number (Neff) given by σ2PA(GM) = (079 ± 0.03)Neff2, which is independent of the molecular shape (linear, V or Y-shaped). Therefore, the intramolecular charge transfer responsible for the cooperative effect among the branches does not occur. This statement is corroborated by the results of the femtosecond TAS technique.

Size-dependent photoinduced transparency in colloidal CdTe quantum dots in the strong confinement regime: an inverse linear relationship.

Nanomaterials have been investigated as saturable absorbers for ultrafast lasers because of their large photoinduced transparency related to ground-state bleaching. However, the quantum dot size effect on the photoinduced transparency in the strong confinement regime has not been explored due to the challenge of accurately measuring the ground state and the excited-state absorption cross-sections. At the same time, these optical properties are essential to calculate several chemical and physical quantities at the nanoscale. In this context, we have employed the photoluminescence saturation method to determine the ground-state absorption cross-section and the femtosecond open-aperture Z-scan technique to investigate the size-dependent ground-state bleaching of glutathione-capped CdTe QDs synthesized in an aqueous medium. The results were modeled using rate equations within the three-energy levels approach. Our results pointed out that the photoinduced transparency rate at the 1S3/2(h) → 1S(e) transition peak presents an inverse linear relationship with the QD diameter (from 2.2 nm up to 3 nm). Otherwise, the larger QDs have a higher ground-state cross-section, which is directly proportional to the ground-state bleaching. To explain this apparent contradiction, we calculate the effective absorption coefficient αeff = σ/V (σ is the absorption cross section and V is the QD volume) for the QDs and observed that the smaller QDs have a higher absorption from the ground to the first excited state, corroborating our results. Finally, our results showed that the saturable absorption effect in CdTe-QDs is slightly higher than that obtained for graphene and other 2D materials and smaller than the black phosphorus in the visible region.

Modeling the First-Order Molecular Hyperpolarizability Dispersion from Experimentally Obtained One- and Two-Photon Absorption.

The search for optical materials, particularly organic compounds, is still an attractive and essential field for developing several photonic devices and applications. For example, some applications are based on light scattering with twice the energy of the incoming photon for selected compounds, that is, the nonlinear optical effect related to the second-order susceptibility term from the electronic polarization expression. The microscopic interpretation of this phenomenon is called the first-order molecular hyperpolarizability or incoherent second harmonic generation of light. Understanding such phenomena as a function of the incoming wavelength is crucial to improving the optical response of future materials. Still, the experimental apparatus, hyper-Rayleigh scattering, apparently simple, is indeed a challenging task. Therefore, we proposed a proper alternative to obtain the dispersion of the first-order hyperpolarizability using the well-known one- and two-photon absorption techniques. By the spectral analysis of both the spectra, we gathered spectroscopic parameters and applied them for predicting the first-order hyperpolarizability dispersion. This prediction is based on an n-level energy system, taking into account the position and magnitude of transition dipole moments and the difference between the permanent dipole moment of the n-excited states. Moreover, using the presented method, we can avoid underestimating the first-order hyperpolarizability by not suppressing higher-energy transitions. Quantum chemical calculations and the hyper-Rayleigh scattering technique were used to validate the proposed method.

Unconventional Disorder by Femtosecond Laser Irradiation in Fe2O3.

This paper demonstrates that femtosecond laser-irradiated Fe2O3 materials containing a mixture of α-Fe2O3 and ε-Fe2O3 phases showed significant improvement in their photoelectrochemical performance and magnetic and optical properties. The absence of Raman-active vibrational modes in the irradiated samples and the changes in charge carrier emission observed in the photocurrent density results indicate an increase in the density of defects and distortions in the crystalline lattice when compared to the nonirradiated ones. The magnetization measurements at room temperature for the nonirradiated samples revealed a weak ferromagnetic behavior, whereas the irradiated samples exhibited a strong one. The optical properties showed a reduction in the band gap energy and a higher conductivity for the irradiated materials, causing a higher current density. Due to the high performance observed, it can be applied in dye-sensitized solar cells and water splitting processes. Quantum mechanical calculations based on density functional theory are in accordance with the experimental results, contributing to the elucidation of the changes caused by femtosecond laser irradiation at the molecular level, evaluating structural, energetic, and vibrational frequency parameters. The surface simulations enable the construction of a diagram that elucidates the changes in nanoparticle morphologies.

Effective π-electron number and symmetry perturbation effect on the two-photon absorption of oligofluorenes.

Fluorene-based molecules exhibit significant nonlinear optical responses and multiphoton absorption in the visible region, which, combined with the high fluorescence quantum yield in organic solvents, could make this class of materials potentially engaging in diverse photonics applications. Thus, herein, we have determined the two-photon absorption (2PA) of oligofluorenes containing three, five, and seven repetitive units by employing the wavelength-tunable femtosecond Z-scan technique. Our outcomes have shown that the 2PA cross-section in oligofluorenes presents an enhanced value of around 18 GM per Neff, in which Neff is the effective number of π-electrons, for the pure 2PA allowed transition (11Ag-like → 21Ag-like). Furthermore, a weak 2PA transition was observed in the same spectral region strongly allowed by one-photon absorption (11Ag-like → 11Bu-like). This last result suggests a molecular symmetry perturbation, probably induced by the molecular disorder triggered by the increase of moieties in the oligofluorene structure. We have calculated the permanent dipole moment difference related to the lowest-energy transition using the Lippert-Matagaformalism and the 2PA sum-over-states approach to confirm this assumption. Moreover, we have estimated the fundamental limits for the 2PA cross-section in oligofluorenes.

Investigation of the triplet excited state and application of cationic meso-tetra(cisplatin)porphyrins in antimicrobial photodynamic therapy.

In this manuscript, we report, the photophysical study of triplet excited states and antimicrobial photoinactivation of positively charged tetra-cisplatin porphyrin derivatives against Gram + and Gram ‒ bacterial strains. Isomeric cisplatin-porphyrins were used and applied in aPDT assays in the bacilli Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa (Gram negative) and a cocci Staphylococcus aureus (Gram positive) strains. The results show that compound substituted at meta position (3-cis-PtTPyP) is the more efficient photosensitizer against bacteria culture. In this way, tetra-cationic porphyrins containing cisplatin derivatives might be promising aPDT agents with potential applications in clinical infections.

Effects of meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS4) aggregation on its spectral and kinetic characteristics and singlet oxygen production.

The present work reports the effects of meso-tetrakis (4-sulfonatophenyl) porphyrin (TPPS4) aggregation on its excited states absorption spectra, triplet states quenching by molecular oxygen and singlet oxygen production. Experimental techniques such as optical absorption, Z-scan with a white light continuum source and the Laser Flash Photolysis were used to fulfil the study. J-aggregates possess reverse saturable absorption in the 505-660 nm spectral range with a peak centered close to 540 nm. These facts together with their fast relaxation time suggest that they can be employed as material for ultrafast optical limiting and switching. Even though aggregation reduces the porphyrin excited-state lifetimes and quantum yields, it does not reduce the probability of the contact between the quencher and the excited aggregate. Aggregation does not change the contribution of energy transfer mechanisms to triplet state quenching by molecular oxygen. The production of singlet oxygen, the intense absorption in the phototherapeutic window and the high efficiency of conversion of light energy into heat, allow consider J-aggregates as a theranostic agent for photomedicine. It is proposed to use J-aggregates for diagnostics by photoacoustic images and in combination with a near-infrared photodynamic/photothermal dual mode therapy, thus improving synergistically the therapeutic response.

Dependent excited state absorption and dynamic of ß-BF2 substituted metalloporphyrins: The metal ion effect.

Absorption and relaxation dynamics of electronic states of free-base, Co(II), Cu(II) and Zn(II) porphyrins bearing a ß-(2,2-difluoro-1,3,2-dioxaborinin-5-yl) group were investigated in dimethyl sulfoxide by using distinct time-resolved spectroscopic techniques. Furthermore, excited state absorption cross-section spectra were determined by combining white light continuum Z-Scan and transient absorption techniques. In the case of the free-base (2H) and Zn(II) porphyrins, we were able to quantify singlet-triplet conversion by analyzing the evolution of time-resolved fluorescence. Relaxation lifetimes from the excited to the ground state were observed in both porphyrins at nanosecond time scale. However, for Co(II) and Cu(II) metalloporphyrins it was observed in the picosecond time scale through femtosecond transient absorption, indicating that both compounds relax back to the ground state only by internal conversion processes. Co(II) and Cu(II) heavy atoms seem to prohibit the radiative and intersystem crossing processes.

Second-order nonlinear optical properties of two chalcone derivatives: insights from sum-over-states.

In this study, a combined experimental and theoretical study of the nonlinear optical properties (NLO) of two chalcone derivatives, (E)-3-(2-methoxyphenyl)-1-(2-(phenylsulfonylamine)phenyl)prop-2-en-1-one (MPSP) and (E)-3-(3-nitrophenyl)-1-(2-(phenylsulfonylamine)phenyl)prop-2-en-1-one (NPSP), in DMSO is reported. The single crystal structures of the compounds, which differ only by the type and position of one substituent, were grown using the slow evaporation technique, and the main structural differences are discussed. The two-photon absorption and first-order hyperpolarizability measurements were performed via the Z-scan technique and hyper-Rayleigh scattering experiment in DMSO. The theoretical calculations were performed using the Density Functional Theory (DFT) at the CAM-B3LYP/6-311++G(d,p) level, and the sum-over-states (SOS) approach in both static and dynamic cases. Besides the electron conjugation achieved by the aromatic rings, olefins, and carbonyl groups, both compounds have a nearly flat chalcone backbone, which is believed to contribute to the nonlinear optical properties. MPSP and NPSP have different positions, even though they have roughly the same conformation and form C-HO interactions. For several studied frequencies, the HRS first hyperpolarizability values for MPSP are greater than those for NPSP, indicating that in most cases the NLO properties of MPSP are better. The comparison among the theoretical and experimental HRS first hyperpolarizability results showed a good agreement. In addition, the two-dimensional second order nonlinear optical spectra obtained from the sum-over-states model indicate good second-order NLO responses of the two chalcone derivatives under external fields. Our findings are important not only to show the potential nonlinear optical application of the two new compounds but also to gain an insight into how different chemical compositions might affect the crystal structures and physico-chemical properties.

Photodynamic and Sonodynamic Therapy with Protoporphyrin IX: In Vitro and In Vivo Studies.

Sono-photodynamic therapy is a promising anticancer technique based on the combination of sonodynamic and photodynamic therapy to improve the cancer treatment effectiveness. This study was aimed at analyzing the effects of the sono-photodynamic (SPD) activity on protoporphyrin IX (PpIX) solution and PpIX-loaded rat liver. In vitro, PpIX 5 µM solutions were irradiated with light (635 nm, 30-50 mW/cm2), ultrasound (1 MHz, 1-2 W/cm2) and both. The PpIX absorption spectra recorded over exposure time revealed that the PpIX decay rate induced by SPD activity (combined irradiation) was approximately the sum of those induced by photodynamic and sonodynamic activity. In vivo, rats were intraperitoneally injected with 5-aminolevulinic acid at the dose of 500 mg/kg weight. After 3 h of injection, the PpIX-loaded livers were irradiated with light (635 nm, 180 ± 9 J/cm2), ultrasound (1.0 MHz, 770 ± 40 J/cm2) and both using a single probe capable of illuminating and sonicating the liver simultaneously. After 30 h, the liver damage induced by each protocol was analyzed histologically. It was found that a greater necrosis depth was induced by the SPD activity. These results suggest that the SPD activity could improve the PpIX decay rate and have greater scope than photodynamic or sonodynamic activity. Further studies should be performed to gain a better understanding of this protocol.

Molecular Structure-Optical Property Relationship of Salicylidene Derivatives: A Study on the First-Order Hyperpolarizability.

The first-order hyperpolarizability of π-conjugated organic molecules is of particular interest for the fabrication of electro-optical modulators. Thus, we investigated the relationship between the molecular structure and the incoherent second-order nonlinear optical response (ßHRS) of four salicylidene derivatives (salophen, [Zn(salophen)(OH2)], 3,4-benzophen, [Zn(3,4-benzophen)(OH2)]) dissolved in DMSO. For that, we employed the Hyper-Rayleigh Scattering technique with picosecond pulse trains. Our experimental results pointed out dynamic ßHRS values between 32.0 ± 4.8 × 10-30 cm5/esu and 58.5 ± 8.0 × 10-30 cm5/esu at 1064 nm, depending on the molecular geometry of the salicylidene molecules. More specifically, the outcomes indicate a considerable increase of ßHRS magnitude (∼30%) when in the ligands are incorporated the Zn(II) ion. We ascribed such results to the rise of the planarity of the π-conjugated backbone of the chromophores caused by the Zn(II). Furthermore, we observed an increase of ∼50% in dynamic ßHRS when there is a replacement of one hydrogen atom (salophen molecule) by an acetophenone group (3,4-benzophen). This result is related to the increase of the effective π-electron number and the higher charge transfer induced at the excited state. All these findings were interpreted and supported in the light of time-dependent density functional theory (DFT) calculations. Solvent effects were considered in the quantum chemical calculations using the integral equation formalism variant of the polarizable continuum model.

Theoretical and Experimental Analysis of Protoporphyrin IX Photodegradation Using Multi-Wavelength Light Sources.

Photodynamic procedures have been used in many applications, ranging from cancer treatment to microorganism inactivation. Photodynamic reactions start with the activation of a photosensitizing molecule with light, leading to the production of cytotoxic molecules that promote cell death. However, establishing the correct light and photosensitizer dosimetry for a broadband light source remains challenging. In this study, we proposed a theoretical mathematical model for the photodegradation of protoporphyrin IX (PpIX), when irradiated by multi-wavelength light sources. The theoretical model predicts the experimental photobleaching (temporal change in PpIX concentration) of PpIX for different light sources. We showed that photobleaching occurs independently of the light source wavelengths but instead depends only on the number of absorbed photons. The model presented here can be used as an important mathematical approach to better understand current photodynamic therapy protocols and help achieve optimization of the doses delivered.

Influence of light intensity and irradiation mode on methylene blue, chlorin-e6 and curcumin-mediated photodynamic therapy against Enterococcus faecalis.

This study aimed to evaluate the effect of the continuous irradiation with low intensity (continuous mode) and fractioned irradiation with high intensity (fractionated mode), keeping the same dose of light by using Light Emitting Diode (LEDs) with wavelength emission centered at 450 and at 660 nm, using methylene blue (MB), chlorin-e6 (Ce6) and curcumin (CUR) as photosensitizers (PSs) against planktonic phase of E. faecalis. Cell viability was assessed by counting colonies forming per mL (CFU/mL), and the quantification of reactive species was performed by fluorescence with the photodegradation rate evaluated by measurements of absorbance of PSs at different times. The results revealed that MB-mediated PDT was efficient to achieve total microbial load reduction in both irradiation modes, but in fractional mode it was possible to use a lower light dose. Using Ce6, a total bacterial reduction was observed when fractional light was used, but at the same light dose, there was no reduction in the continuous irradiation mode. CUR-mediated PDT under continuous irradiation mode promoted the total microbial load reduction. However, for fractional mode, a higher concentration of CUR was required to completely reduce E. faecalis cell viability. Our results suggest that the biological response to PDT is variable depending on the irradiation mode and on the photosensitizer. Therefore, these studies indicate that the irradiation mode, intensity and the specific PSs should be taken into account for the development of clinical protocols for PDT.

Probing the Strong Near-IR Two-Photon Transition in Supramolecular Triphenylamine-based Polymers by Nonlinear Absorption Spectroscopy.

Due to their capability of film formation and remarkable optical features, semiconductor polymers with high two-photon absorption (2PA) have been studied as potential candidates for the development of organic photonic platforms. Furthermore, there is a high demand for photonic devices operating in the near-infrared (IR) region. However, the magnitude of the nonlinear optical response of random coil polymers in the IR region is weak due to the loss of molecular structure caused by increasing the π-conjugated backbone. Thus, herein we aim to investigate the molecular structure and 2PA features relationship for four polymers with supramolecular (helical) rodlike structure. Such polymers have a rigid core based on triphenylamine groups connected to the chiral binaphthalene units and a strong electron-withdrawing group (EWG). This kind of structure allows a very high chromophore density, which was responsible for generating 2PA cross-section between 305 GM and 565 GM in the near-IR (900-1300 nm), depending on the EWG strength. in light of the two-level model within the sum-overstates approach, we estimated the degree of intramolecular charge transfer induced by 2PA in the IR region, and values as high as 50-70% were found. Such a critical outcome allows the 2PA cross-section in the IR region to remain high even though the ratio between the visible/IR-band 2PA cross-section increases as a function of EWG strength.

Unconventional Magnetization Generated from Electron Beam and Femtosecond Irradiation on α-Ag2WO4: A Quantum Chemical Investigation.

Novel magnetic metals and metal oxides that use both the spin and charge of an electron offer exciting technological applications. Their discovery could boost research on functional nanoscale materials. Here, for the first time, we report the magnetization of α-Ag2WO4 under electron beam and femtosecond laser irradiation. The formation and growth of silver oxides (AgO, Ag2O, and Ag3O4) and Ag nanofilaments can be observed on the surface of α-Ag2WO4 crystals. These features were also present in the composition of an extruded material and could open new avenues for surface magnetism studies. In order to understand these results, we used first-principles density functional theory calculations. This allowed us to investigate several potential scenarios for controlling magnetic properties. The effect of electron addition on the crystalline structures of α-Ag2WO4, Ag3O4, Ag2O, and AgO has been analyzed in detail. The creation of Ag and O vacancies on these compounds was also analyzed. Based on structural and electronic changes at the local coordination site of Ag, a mechanism was proposed. The mechanism illustrates the processes responsible for the formation and growth of metallic Ag and the magnetic response to electron beam irradiation.