Photochemical Properties Research Articles

Implementation of bridged copolymerisation to optimise the optical properties of porphyrin: applications in dye-sensitized solar cells

This study explores the concept of all-organic sensitisation of dye-sensitized solar cells (DSSCs) by using a cosensitization approach to model efficient porphyrin-based photosensitizers. The aim is to enhance the absorption defects and light response current of porphyrin dyes, which have been reported in the literature. In this work, eight (8) natural porphyrin derivatives obtained through bridged copolymerisation of free base porphyrin and tetraazaporphyrin have been modelized and analysed. Their geometric parameters, stability energies, chemical stabilities, and photochemical properties were studied using density functional theory (DFT) methods in both gaseous and dichloromethane (DCM) phases. The analysis of photochemical properties, including maximum absorption wavelength ( λ max ), light harvesting efficiency (LHE), electron injection driving force ( Δ G inj ), regeneration driving force ( Δ G reg ), and excited state lifetime ( τ ) of the studied photosensitizers, show significant improvement compared to the parent dye (free base porphyrin) and some recent derivatives SM315 and YD2-o-C8. It is worth noting that the eight ( 8 ) modelled dyes from porphyrin show broader LHE curves not only compared to the parent dye, but also compared to the SM315 dye, which may lead to a higher running photo density. This study highlights the effectiveness of bridged copolymerisation for developing high-performance DSSCS based on porphyrin.

Distyryl Carboxylic Acid Substituted BODIPY and BODIPY‐C60 Systems for Generation of Singlet Oxygen

AbstractBODIPY based molecules functionalized with water soluble moieties have been developed and recognized as liable triplet photosensitizers for phototherapeutic applications. In this work, we have prepared BODIPY analogues with dicarboxylic acid groups and bearing iodine or fullerene moieties for efficient intersystem crossing which display far‐red absorption band and high singlet oxygen production both in organic and aqueous media. In this perspective by using similar design the effect of the halogenation of the dyes versus spin converter on the skeleton were compared. The structures of the synthesized BODIPYs and BODIPY‐C60 (6–10) were elucidated by mass, 1H and 13C NMR spectroscopic techniques. Photophysical and photochemical properties of the compounds were examined using UV‐Vis. absorption and fluorescence emission spectrophotometers. The absorption intensities of the trap molecules (DPBF and ADBA) reduced because of singlet oxygen generation in the media. This study may provide useful infrastructure to elucidate the relationship between the use of fullerene (9) or iodine (10) where singlet oxygen quantum yield of 9 and 10 are determined as 0.87 and 0.97 respectively.

Substituent effect on the electronic and optical properties of newly designed pyrrole derivatives using density functional theory

Abstract This work explores six newly designed compounds obtained by several substitutions in 2,5-di(2-thienyl) pyrrole molecule. For this series of compounds, the electronic and optical properties were investigated using density functional theory and time-dependent density functional theory (TD-DFT). The new compounds were characterized by calculating the chemical parameters that correlated with their optical and electrical properties. The lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO) energies are calculated using the B3LYP functional with the 6-311G (d, p) basis set. The most low-lying energy level of the LUMO was found for Perr-NO2, indicating its effective electron injection capabilities and oxidation resistance. The HOMO and LUMO distributions of Perr-Cl and Perr-NO2 displayed a remarkable complementarity throughout each component of the two compounds, indicating an effective intermolecular charge transfer. The molecular electrostatic potential analysis demonstrated that the proposed compounds have a broad distribution of electrophilic and nucleophilic sites, which predict a high degree of chemical reactivity. The electron density analysis at the bonding and anti-bonding sites of the title compounds was performed using the electron localization function and local orbital locator techniques. Non-covalent interaction analysis using the reduced density gradient approach classified all types of interaction: repulsive, weak, and attractive interactions within compound fragments. All compounds exhibited a robust repulsive interaction, as proved by the red spikes at 0.038 a.u. The ultraviolet/visible (UV/vis) spectrum was obtained by TD-DFT using CAM-B3LYP models in conjunction with 6-311G (d, p) basis set and methanol as a solvent, the absorption bands were found within the UV range, and the maximum wavelength showed red-shifted increases. These compounds could serve as a base material for developing selective gas sensors with considerable UV/vis absorption (180–400 nm). According to the research results, the designed compounds are good candidates for use as precursors in polymer designs for optoelectronic and sensor applications due to their high electrical conductivity and photochemical properties.

Premise setting for sustainable developing adsorption in environmental remediation using graphitic carbon nitride@agar-derived porous carbon composite

In the adsorption process for wastewater treatment, the adsorbent plays an important role. A composite adsorptive material composed of graphitic carbon nitride and agar-derived porous carbon (CNPC) was fabricated from simple precursors (melamine, thiourea, and agar) and through a facile procedure with different melamine and thiourea ratios. Characterization of CNPC proved a successful formation of a porous structure consisting of mesopores and macropores, wherein CNPC holds distinctive electrochemical (lowered resistance and higher specific capacity) and photochemical properties (lowered bandgap to 2.33 eV) thanks to the combination of graphitic carbon nitride (CN) and agar-derived porous carbon (PC). Inheriting the immanent nature, CNPC was subjected to the adsorption of methylene blue (MB) dye in an aqueous solution. The highest adsorption capacity was 133 mg/g for CNPC-4 which was prepared using a melamine to thiourea ratio of 4:4 – equivalent to the removal rate of 53.2 % and following the pseudo-I-order reaction rate. The effect of pH points out that pH 7 and 9 were susceptible to maximum removal and pretreatment is not required while the optimal ratio of 7.5 mg of MB and 30 mg of material was also determined to yield the highest performance. Furthermore, the reusability of the material for three consecutive cycles was evaluated based on two methods pyrolysis at 200 °C and photocatalytic degradation by irradiation under visible light. In general, the photocatalytic regeneration pathway is more ample and efficient than pyrolysis in terms of energy efficiency (saving energy over 10 times) and adsorption capacity stability. As a whole, the construction of accessible regenerative and stable adsorbent could be a venturing step into the sustainable development spearhead for industries.

Anticancer photodynamic activities of triphenylphosphine-labelled phthalocyanines and their bovine serum albumin-gold nanoparticles- complexes on melanoma A375 cell lines in vitro

This work reports on the synthesis of triphenylphosphine-labelled cationic phthalocyanines (Pc) complexed with bovine serum albumin (BSA) and gold nanoparticles (Au NPs). This nano-complex (Pc-BSA-Au) is studied for its photodynamic therapy (PDT) activity compared to the non-complexed Pc counterpart. The photochemical properties and in vitro PDT efficacies of the Pc and the nano-complex were determined and are compared herein. The singlet oxygen (1O2) yields of the Pcs were determined and are reported in DMF. A singlet oxygen quantum yield of 0.47 was obtained for the Pcs. The PDT efficacies of the complexes were thereafter determined using malignant melanoma A375 cancer cell line in vitro. An increase in the cell toxicity was observed for cells treated with Pc-BSA-Au compared to those treated with the Pc alone. The cell survival percentages were 23.1% for cells treated with Pc-BSA-Au and 48.7% for those treated with Pc alone under PDT treatments.

Construction of Highly Functionalized 2-Styrylfurans by N-Heterocyclic Carbene/Brønsted Acid Catalysis.

This research presents an original method for synthesizing styrylfurans using N-heterocyclic carbenes (NHCs) and Brønsted acid catalysis. By exploiting 2,4-dioxoesters as conjugated 1,3-dicarbonyls, we have developed a technique allowing the efficient formation of highly functionalized styrylfurans with interesting photochemical properties, through a NHC-catalyzed cross-benzoin reaction followed by a Brønsted acid-driven Paal-Knorr-like condensation. This approach permits the integration of various substituents on the furan ring, with preliminary biological studies indicating potential as fluorescent dyes.

Insights into the Role of Photobleaching on the Photophysical and Photochemical Properties of Dissolved Black Carbon

Insights into the Role of Photobleaching on the Photophysical and Photochemical Properties of Dissolved Black Carbon

Synthesis of a new Zn-phthalocyanine, photophysical, photochemical, and sono-photochemical properties and DFT studies

In recent years cancer has become a global problem and burden to the health system. Photodynamic therapy (PDT) and sonodynamic therapy (SDT) are promising alternatives for cancer treatment. It is very important to use phthalocyanines as sensitizers in such treatments. In this study, a new type of Zn-phthalocyanine compound (2) peripherally substituted with 4-Hydroxy-7-methoxyquinoline was synthesized and characterized, and its photodynamic and sono-photodynamic efficiencies were examined. Additionally, the electronic and spectroscopic properties of the compounds were calculated theoretically using Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TD-DFT) methods. The effect of the solvent on the reactivity of the compounds was examined by the Conductive-Like Polarizable Continuum Model (CPCM). The results have indicated that singlet oxygen quantum yield has increased in the sono-photochemical study (ΦΔ=0.98) compare to the photodynamic study (ΦΔ=0.70). Experimental and theoretical study results show that the reactivity of the new ligand increases with Zn metal.

Dissolved organic matter isolates obtained by solid phase extraction exhibit higher absorption and lower photo-reactivity: Effect of components

Notable differences in photo-physical and chemical properties were found between bulk water and solid phase extraction (SPE) isolates for dissolved organic matter (DOM). The moieties extracted using modified styrene divinylbenzene cartridges, which predominantly consist of conjugated aromatic molecules like humic acids, contribute mainly to light absorption but exhibit lower quantum yields of fluorescence and photo-produced reactive intermediates (PPRIs). Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) revealed lignin as the moieties displaying most significant variance in abundance. In Van Krevelen-Spearman plot, we observed molecules positively or negatively correlated with DOM's optical and photochemical properties (including SUVA254, steady-state concentrations of ·OH, 1O2 quantum yield, etc.) were confined to specific regions, which can be delineated using a threshold modified aromaticity index (AImod) of 0.3. Based on the relationships between optical properties and PPRI production, it is suggested that the energy gap between ground state and excited singlet state (△ES1→S0), governing the inner conversion rate, serves as a determinant for apparent quantum yield of PPRIs in DOM, with intra-molecular charge transfer (CT) interactions potentially playing a pivotal role. Regarding DOM's photoreactivity with pollutants, this study has revealed, for the first time, that protein/amino sugars/amino acids could act as antioxidant groups in addition to phenols on the photolysis of sulfadiazine. These findings provide valuable insights into DOM photochemistry and are expected to stimulate further research in this area.

Double Catalytic Activity Unveiled: Synthesis, Characterization, and Catalytic Applications of Iridium Complexes in Transfer Hydrogenation and Photomediated Transformations.

Iridium complexes have been demonstrated to be highly active catalysts for a wide variety of transformations. Their unique photophysical and photochemical properties render them as one of the most established photocatalysts. Moreover, iridium complexes are widely acknowledged for their efficiency in transfer hydrogenation reactions. However, the development of iridium complexes able to promote both traditional organometallic catalysis and photocatalysis is scarce. Thus, the design of iridium-based catalysts is still an active area of research. In this context, we targeted the synthesis of a family of Ir-Cp* systems to explore their (photo)catalytic applications. Here, we describe the synthesis, structural characterization, and photophysical properties of iridium complexes of formula [IrCp*Cl(N^O)]. These complexes have been applied with a double catalytic function, in transfer hydrogenation for carbonyl reduction and in different photomediated transformations.

Iron(III) Carbene Complexes with Tunable Excited State Energies for Photoredox and Upconversion.

Substituting precious elements in luminophores and photocatalysts by abundant first-row transition metals remains a significant challenge, and iron continues to be particularly attractive owing to its high natural abundance and low cost. Most iron complexes known to date face severe limitations due to undesirably efficient deactivation of luminescent and photoredox-active excited states. Two new iron(III) complexes with structurally simple chelate ligands enable straightforward tuning of ground and excited state properties, contrasting recent examples, in which chemical modification had a minor impact. Crude samples feature two luminescence bands strongly reminiscent of a recent iron(III) complex, in which this observation was attributed to dual luminescence, but in our case, there is clear-cut evidence that the higher-energy luminescence stems from an impurity and only the red photoluminescence from a doublet ligand-to-metal charge transfer (2LMCT) excited state is genuine. Photoinduced oxidative and reductive electron transfer reactions with methyl viologen and 10-methylphenothiazine occur with nearly diffusion-limited kinetics. Photocatalytic reactions not previously reported for this compound class, in particular the C-H arylation of diazonium salts and the aerobic hydroxylation of boronic acids, were achieved with low-energy red light excitation. Doublet-triplet energy transfer (DTET) from the luminescent 2LMCT state to an anthracene annihilator permits the proof of principle for triplet-triplet annihilation upconversion based on a molecular iron photosensitizer. These findings are relevant for the development of iron complexes featuring photophysical and photochemical properties competitive with noble-metal-based compounds.

High performance catalyst for metal catalysis coupled with photocatalysis and its catalytic ammonia borane methanolysis for hydrogen production

In the study, the influence and mechanisms of metal and non-metal dopants on the photochemical properties of the semiconductor catalyst g-C3N4 are investigated. The results reveal that doping Ni, Ru, and B on g-C3N4 results in significant alterations to the energy band structure, the band gap value decreases to 0.78 eV (Ru@g-C3N4), 0.69 eV (Ni@g-C3N4), 0.5 eV (RuB@B-g-C3N4), and 0.1 eV (NiB@B-g-C3N4) from the original value of 1.139 eV. The doping of metal and non-metal atoms can significantly enhance the light absorption capability and photothermal conversion efficiency of B-g-C3N4. The mechanism of ammonia borane (AB) dehydrogenation follows the stepwise dehydrogenation principle. AB molecules adsorb onto the active metal centers, and with the assistance of the catalytic sites, CH3OH molecules activate and attack the B–N bond in AB molecules, leading to the initial breakage of the B–N bond, the interaction between O atoms in CH3OH and N atoms in AB continues, forming NH3BH2(OCH3). Interactions between H(B) and H(O) result in the production of H2, the energy barrier for this reaction is 34.14 kcal/mol. Compared to dark conditions, RuB@B-g-C3N4 exhibits higher catalytic activity under light irradiation, the reaction time from 9′20″ reduce to 8′. This shows that there is a synergistic effect between photocatalytic AB methanolysis and conventional metal catalyzed AB methanolysis in the RuB@B-g-C3N4 catalytic system. The study provides the novel way for the development of dual-function catalysts combining metal catalysis and photocatalysis through Ru and B modification of g-C3N4.

Coumarin based glyoxylate photoinitiators for free radical and cationic Photopolymerizations with UV-Visible LED irradiation

High-performance photoinitiators (PIs) play a crucial role in ultraviolet–visible (UV–Vis) photopolymerization. In this study, three coumarin-3-oxoacetic acid methyl esters (COAEs) which demonstrate significant UV–Vis absorption within the 300–500 nm range were synthesized and studied. Real-time fourier transform infrared (RT-FTIR) and photo-differential scanning calorimetry (photo-DSC) experiments demonstrated that these PIs can function as Type I and Type II PIs for initiating free radical polymerization (FRP) of acrylate monomers. Additionally, they can serve as photosensitizers for iodonium salts and sulfonium salts, enabling cationic photopolymerization (CP) of epoxy and oxetane monomers. Remarkably, even at low concentrations of 0.01 wt%, they can effectively initiate the deep curing of Tri-(propylene glycol) diacrylate (TPGDA) to a depth of approximately 9 cm after 5 min of irradiation with a 415 nm or 450 nm LED light source. Furthermore, the COAEs exhibit satisfactory photobleaching properties, making them suitable for colorless applications in photopolymerization. The photochemical and photophysical properties of the COAEs were thoroughly investigated using absorption spectroscopy, electron spin resonance, cyclic voltammetry experiments, and photoinduced decarboxylation experiments to elucidate the photoinitiation mechanism. Cytotoxicity experiments revealed that COAE-N exhibited good cytocompatibility. Therefore, the exceptional polymerization properties of COAEs offer promising prospects for FRP and CP applications. Additionally, their efficient photobleaching characteristics make them highly suitable for deep photopolymerization applications. Moreover, the low cytotoxicity of COAEs suggests significant potential for biomedical applications such as dental restoration.

Going cresyl for plant cell imaging

The adventof fluorescent probesand the characterization of their photochemical properties in the past years allowed significant advances in the studies ofspatiotemporal cellular processes within complex and crowded systems.Dyesareindeedextremely useful tools forthe visualization ofcellular and subcellular structures present in living cells, as well asto studytheirdynamicand molecular composition or physiological changes. There are some areas of plant cell biology that have been more challenging to explore due to the physiology and organization of certain endomembrane compartments. In this study we characterize the labeling properties of cresyl violet as quick and inexpensive imaging agent for tracking endosomes, vacuole compartments which are usually very differentiated and categorized as more acidic as well as acidic plant compartments. Its photobleaching, labelling and cytotoxic properties are compared with other well-known and currently most used synthetic and molecular probes.

Synthesis of bis-(benzhydryloxy) substituted axially silicon(IV) phthalocyanine: investigation of photophysical, photochemical, and computational electronic properties

Synthesis of axially disubstituted silicon(IV) phthalocyanine bearing benzhydryloxy groups obtained by reaction of SiPcCl2 with diphenylmethanol is reported. Characterization of the compound was performed by 1H and 13C NMR, UV–Vis, mass spectrometry, and FT-IR spectroscopy. Photophysical and photochemical properties were investigated. Fluorescence spectra measurements were performed in DMSO as solvent. A preferred chemical method was used to determine the amount of singlet oxygen production. Optimizations were calculated for the single-molecule Si-Pc with the 6–311 G (d, p) basis set at the B3LYP and B3PW91 levels of density functional theory (DFT). The charge transfer (or) charge delocalization between intramolecular donor–acceptor groups was determined by NBO analysis. Furthermore, molecular electrostatic potential, Fukui functions, electrophilic and nucleophilic character maps were calculated. The electronic structure and energy parameters of the investigated compound were determined to be ΔE calc = 2.19 eV by DFT calculation and ΔE opt = 1.84 by experimental UV spectrum.

NIR dye-based electrospun fibers for antimicrobial photodynamic therapy

AbstractAntimicrobial photodynamic therapy (aPDT) has emerged as a promising strategy to improve antimicrobial treatment and face the antibiotic resistance to conventional therapy. Among the different photosensitizers, Near Infrared (NIR) polymethine dyes (Squaraines, SQs and Cyanines, CYs) have attracted considerable attention although, their poor aqueous solubility and stability still limit their application. Their incorporation inside nanoparticles (NPs) or into electrospun fibers, could help to prevent dye aggregation, protect their photochemical properties, and play a key role in the infection treatment.Cys and SQs were characterized before and after the incorporation, showing improved optical properties and photostability. In addition, their ability to produce Reactive Oxygen Species (ROS), responsible of bacterial death, was evaluated, proving that the ROS generation ability is preserved after the incorporation. Furthermore, in vitro antimicrobial studies against Gram-negative and Gram-positive models showed a good antimicrobial effect after the irradiation, confirming the potential of these nanophotosensitizers for aPDT in the local treatment of infections.

Fungal Photosensitizers – A new Scaffold of Tailor-made Photoantimicrobials?

SignificanceNew antimicrobials are needed to meet the challenges posed by increasing levels of antimicrobial resistance. While fungi are recognized as valuable source for antibiotics, their potential to produce photoantimicrobials has not been fully explored. ApproachFungal photosensitizers were isolated from the colorful fruiting bodies of dermocyboid Cortinarius species. Their photoantimicrobial potential was evaluated using a high-throughput assay based on a modified EUCAST protocol. Photocytotoxicity studies and near infrared emission spectra were conducted to characterize the photochemical properties of our compounds. ResultsPotent, novel photoantimicrobials against bacteria and yeasts were identified with activities in the low micromolar/nanomolar range. In addition, action solely against microbes was demonstrated for selected fungal photosensitizers. ConclusionsFungi are an underexplored source of promising photoantimicrobials with broad-spectrum antimicrobial activity.

Aryl Azocyclopropeniums: Minimalist, Visible-Light Photoswitches.

We report convenient syntheses of aryl azocyclopropeniums and a study of their photochemical properties. Incorporation of the smallest arene leads to pronounced redshift of the π-π* absorbance band, compared to azobenzenes. Photoisomerization under purple or green light irradiation affords Z- or E-isomers in ratios up to 94% Z or 90% E, and the switches proved stable over multiple irradiation cycles. Thermal half-lives of metastable Z-isomers range from minutes to hours in acetonitrile and water. These properties together with the concise, versatile syntheses render aryl azocyclopropeniums exciting additions to the tool kit of readily available molecular photoswitches for wide ranging applications.

Ultrafast spectroscopy study of DNA photophysics after proflavine intercalation.

Proflavine (PF), an acridine DNA intercalating agent, has been widespread applied as an anti-microbial and topical antiseptic agent due to its ability to suppress DNA replication. On the other hand, various studies show that PF intercalation to DNA can increase photogenotoxicity and has potential chances to induce carcinomas of skin appendages. However, the effects of PF intercalation on the photophysical and photochemical properties of DNA have not been sufficiently explored. In this study, the excited state dynamics of the PF intercalated d(GC)9 • d(GC)9 and d(AT)9 • d(AT)9 DNA duplex are investigated in an aqueous buffer solution. Under 267nm excitation, we observed ultrafast charge transfer (CT) between PF and d(GC)9 • d(GC)9 duplex, generating a CT state with an order of magnitude longer lifetime compared to that of the intrinsic excited state reported for the d(GC)9 • d(GC)9 duplex. In contrast, no excited state interaction was detected between PF and d(AT)9 • d(AT)9. Nevertheless, a localized triplet state with a lifetime over 5 µs was identified in the PF-d(AT)9 • d(AT)9 duplex.

Photochemical Carbocatalysis: Fullerene‐, Carbon Nanotube‐ or Graphene‐Based Metal‐Free Photocatalysts for Organic Transformations

AbstractSynthetic photochemistry is a research field, where organic transformations are promoted by the presence of photoactive species, under light irradiation. In particular, the sub‐field of photoorganocatalysis, where organic molecules are used as photocatalysts, has been launched as a “green” and sustainable approach. Carbon allotrope nanostructures (CANs) and their derivatives exhibit unique photophysical and photochemical properties, which have been exploited for the preparation of efficient metal‐free and sustainable photocatalytic systems. This review summarizes the progress on the field of photochemical carbocatalysis, presenting the achievements by fullerene‐, carbon nanotube‐ and graphene‐based nanomaterials. Additionally, future prospects for CAN‐based nanomaterials as photochemical promoters for organic transformations are also mentioned.