Blue LED Irradiation Research Articles

A Paternò-Büchi Reaction of Aromatics with Quinones under Visible Light Irradiation.

Reported herein is a Paternò-Büchi reaction of aromatic double bonds with quinones under visible light irradiation. The reactions of aromatics with quinones exposed to blue LED irradiation yielded oxetanes at -78 °C, which was attributed to both the activation of double bonds in aromatics and the stabilization of oxetanes by thiadiazole, oxadiazole, or selenadiazole groups. The addition of Cu(OTf)2 to the reaction system at room temperature resulted in the formation of diaryl ethers via the copper-catalyzed ring opening of oxetanes in situ. Notably, the substrate scope was extended to general aromatics.

The role of photo‐catalytically synthesized poly (N‐vinyl pyrrolidone‐methyl methacrylate)/CuO‐rGO nanocomposite as a filler for the reinforcement for epoxy system

AbstractThis study demonstrates the effective copolymerization of N‐Vinyl pyrrolidone and methyl methacrylate using reduced graphene oxide adorned with copper oxide nanoparticles (CuO‐rGO) acting as a catalyst when exposed to blue LED irradiation to generate random copolymer hybrid system of P(NVP‐co‐MMA/CuO‐rGO). We investigated the effects of this copolymer hybrid system of P(NVP‐co‐MMA/CuO‐rGO) on the mechanical, thermal and antibacterial properties of epoxy (DEGBA‐DETDA) composite. By employing two different concentrations of CuO nanoparticle, we assessed the reinforcement capability of the synthesized copolymer‐nanoparticle hybrid within an epoxy matrix. We observed that the composite sample comprising P(NVP‐co‐MMA/CuO‐rGO), having 0.5% of CuO‐rGO (Cu002) with respect to the epoxy concentration resulted in significant enhancements in fracture toughness. Further mechanical properties and thermal properties of the composite samples were studied using DMA, DSC and TGA. Microstructural properties and Mechanisms of toughening are elucidated through the examination of SEM images depicting the fracture surfaces. Moreover, the hybrid composites exhibited notable antibacterial activity against both E. coli and S. aureus compared to control. These findings highlight the copolymer hybrid P(NVP‐co‐MMA/CuO‐rGO) system's role as a multifunctional filler, enhancing epoxy composites' durability, functionality, and antibacterial performance. Our work advances the field of composites by showcasing the customized use of nanoparticle‐enhanced copolymers to improve material properties, providing valuable insights for the development of next‐generation composite materials.Highlights Achieved novel copolymerization of N‐Vinyl pyrrolidone and methyl methacrylate. CuO‐rGO successfully facilitates P(NVP‐co‐MMA/CuO‐rGO) nanocomposite formation. P(NVP‐co‐MMA/CuO‐rGO) nanocomposite proved as an effective filler for epoxy. P(NVP‐co‐MMA/CuO‐rGO) reinforced epoxy enhances toughness by 143% over neat epoxy Reinforced epoxy showed better efficacy against E. coli & S. aureus versus control.

Antimicrobial photodynamic therapy against a dual-species cariogenic biofilm using a ruthenium-loaded resin-based dental material

BackgroundStreptococcus mutans and Candida albicans are associated with caries recurrence. Therefore, this study evaluated the combination of a Ru(II)-loaded resin-based dental material (RDM) and antimicrobial photodynamic therapy (aPDT) against a dual-species biofilm of S. mutans and C. albicans. MethodsAn aPDT protocol was established evaluating Ru(II)'s photocatalytic activity and antimicrobial potential under blue LED irradiation (440–460 nm, 22.55 mW/cm2) at different energy densities (0.00, 6.25, 20.25, 40.50 J/cm2). This evaluation involved singlet oxygen quantification and determination of minimum inhibitory concentration (MIC) and minimum bactericidal/fungicidal concentration (MBC/MFC). The biofilm was grown (72 h) on resin disks prepared with Ru(II)-doped RDM (0.00, 0.56, or 1.12 %) and samples were exposed to aPDT or dark conditions. The biofilm was then harvested to analyze cell viability (CFU counts) and formation of soluble and insoluble exopolysaccharides. ResultsThe photocatalytic activity of Ru(II) was concentration and energy density dependent (p < 0.05), and MIC/MBC values were reduced for the microorganisms after LED irradiation (40.5 J/cm2); therefor, this energy density was chosen for aPDT. Although incorporation of Ru(II) into RDM reduced the biofilm growth compared to Ru(II)-free RDM for both species in dark conditions (p < 0.05), aPDT combined with an Ru(II)-loaded RDM (0.56 or 1.12 %) potentialized CFU reductions (p < 0.05). Conversely, only 1.12 % Ru(II) with LED irradiation showed lower levels of both soluble and insoluble exopolysaccharides compared to Ru(II)-free samples in dark conditions (p < 0.05). ConclusionsWhen the Ru(II)-loaded RDM was associated with blue LED, aPDT reduced cell viability and lower soluble and insoluble exopolysaccharides were found in the cariogenic dual-species biofilm.

Photocatalytic Cyclization Cascades by Radical Relay toward Pyrrolo[1,2-a]indoles: Synthesis, Mechanism, and Application.

A photocatalytic annulation cascade of unactivated N-alkene-linked indoles with Langlois' reagent by a radical relay is developed at room temperature under blue LED irradiation. The reaction afforded a series of tri/difluoromethylated pyrrolo[1,2-a]indoles in moderate to good yields. The DFT study suggests that the reaction is ascribed to a rhodamine 6G-induced cyclization cascade involving vinyl addition-radical relay and hydrogen-atom-abstraction (HAA) processes, and interestingly, pyrrolo[1,2-a]indoles are applied as fluorescent dyes into the fluorescence spectrum and live-cell imaging. This paper represents an initial example on photocatalytic cyclization cascades by radical relay and the HAA process.

Photocatalytic Oxidative Cleavage of Alkenes Followed by Carbonyl Stereoselective Bioreduction for the Synthesis of Enantioenriched Secondary Alcohols

AbstractOxidative alkene cleavage of a series of (hetero)aryl alkyl styrenes in aqueous medium has been developed using either 9‐mesityl‐10‐methylacridinium perchlorate ([AcrMes]ClO4) and sodium anthraquinone‐2‐sulfonate (SAS) as photosensitizers under blue LED irradiation. Reaction conditions were studied to find a suitable media for the development of a linear cascade after subsequent stereoselective reduction of the corresponding ketone intermediate. The use of cesium carbonate provided an adequate pH to the reaction medium for the alcohol dehydrogenase action. [AcrMes]ClO4 was found to be the best photocatalyst, allowing the development of concurrent or sequential cascades depending on the ability of the photosensitizer to oxidize back the chiral alcohol to the ketone. Overall, the photobiocatalytic approach has allowed the synthesis of a wide number of alcohol compounds, the formation of (S)‐ or (R)‐enantiomers being attained with excellent stereoselectivity and moderate to good yields.

Thiourea as a precatalyst for the electron donor–acceptor complex photoactivation platform of oxime esters

A novel electron donor–acceptor (EDA) complex catalysis strategy has been developed using thiourea as a precatalyst under blue LED irradiation. Using 2–5 mol% of thiourea, various nitrogen-containing compounds were successfully synthesized.

Dehydrogenative cyclization of 2-arylbenzoic acid and 2-arylbenzamide with hydrogen evolution in a photoelectrochemical cell.

This paper describes photoelectrochemical dehydrogenative cyclization of 2-arylbenzoic acid and 2-arylbenzamide in a PEC cell consisting of a mesoporous WO3 photoanode and Pt cathode. The cyclization reaction is effectively driven by this PEC system at room temperature with blue LED irradiation under external oxidant- and metal-free conditions, delivering a series of benzolactones and benzolactams in up to 95% isolated yields. Meanwhile, hydrogen is released as the only byproduct of this process.

Phosphonate-substituted porphyrins as efficient, cost-effective and reusable photocatalysts.

Recent advances in visible light photocatalysis represent a significant stride towards sustainable catalytic chemistry. However, its successful implementation in fine chemical production remains challenging and requires careful optimization of available photocatalysts. Our work aims to structurally modify bioinspired porphyrin catalysts, addressing issues related to their laborious synthesis and low solubility, with the goal of increasing their efficiency and developing reusable catalytic systems. We have demonstrated the catalytic potential of readily available meso-tetrakis[4-(diethoxyphosphoryl)phenyl]porphyrins (M(TPPP)). Novel metal (Pd(II), Co(II) and In(III)) complexes with this ligand were prepared in good yields. These chromophores were characterized in solution using spectroscopic (NMR, UV-vis, fluorescence) and electrochemical methods. The introduction of phosphonate groups on the phenyl substituents of meso-tetraphenylporphyrins (M(TPP)) improves solubility in polar organic solvents without significantly altering the photophysical properties and photostability of complexes. This structural modification also leads to easier reductions and harder oxidations of the macrocycle for all investigated complexes compared to the corresponding TPP derivatives. The free base porphyrin, zinc(II), palladium(II), and indium(III) complexes were studied as photocatalysts for oxidation of sulfides to sulfoxides using molecular oxygen as a terminal oxidant. Both dialkyl and alkyl aryl sulfides were quantitatively transformed into sulfoxides under blue LED irradiation in the acetonitrile-water mixture (10 : 1 v/v) with a low loading (0.005-0.05 mol%) of porphyrin photocatalysts, where H2(TPPP) and Pd(TPPP) were found to be the most efficient. The reaction mechanism was studied using photoluminescence and EPR spectroscopies. Then, to access reusable catalysts, water-soluble derivatives bearing phosphonic acid groups, H2(TPPP-A) and Pd(TPPP-A), were prepared in high yields. These compounds were characterized using spectroscopic methods. Single-crystal X-ray diffraction analysis of Pd(TPPP-A) reveals that the complex forms a 3D hydrogen-bonded organic framework (HOF) in the solid state. Both H2(TPPP-A) and Pd(TPPP-A) were found to catalyze the photooxidation of sulfides by molecular oxygen in the acetonitrile-water mixture (1 : 1 v/v), while only Pd(TPPP-A) resulted in selective production of sulfoxides. The complex Pd(TPPP-A) was easily recovered through extraction in the aqueous phase and successfully reused in five consecutive cycles of the sulfoxidation reaction.

Bisphosphonium salt catalyzed [3 + 2] annulation of N-tosylimino(iso)quinolinium ylides with aryl olefins under blue LED irradiation

A visible-light-induced [3 + 2] annulation of N-tosylimino(iso)quinolinium ylides with aryl olefins, catalyzed by a bisphosphonium salt has been developed. Furthermore, the synthesis method of the bisphosphonium salts was improved.

Photo-induced catalyst-free formal carbon insertion of acylsilanes into B–B and B–Si bonds

A formal carbon insertion of acylsilanes into B–B and B–Si bonds has been developed. The in situ formed siloxycarbene under blue LED irradiation worked as the intermediate for the reaction. When 2-furyl and 2-thiophenyl acylsilanes were used, the B(pin) ring was enlarged to a six-membered ring.

New insight into highly efficient CSA@g-C3N4 for photocatalytic oxidation of benzyl alcohol and thioanisole: NAEDS as a promoter of photoactivity under blue LED irradiation.

An open new perspective has been established toward synthesizing eco-friendly CSA@g-C3N4 employing surface engineering. The carbon nitride modified through camphorsulfonic acid was designed and developed in a category of the new generation of photocatalysts for the oxidation of benzyl alcohol and thioanisole in the existence of a natural deep eutectic solvent (NADES). In comparison with pure g-C3N4, not only does CSA@g-C3N4 exhibit an extraordinarily higher ability for harvesting visible light stemming from declining the recombination rate of electrons/holes dependent on PL results but it also reveals notable photocatalytic oxidation capability in the transformation of alcohols as well as thiols into relevant compounds. In addition, non-metal compound (CSA) incorporation would result in considerably diminishing the energy band gap value from 2.8 to 2.28 eV to escalate the visible-light absorption of g-C3N4. While the conventional consensus implies that inherent properties of photocatalysts bring on high photoactivity, this study indicates that deploying choline chloride-urea deep eutectic solvent as an external factor plays the role of photoactivity accelerator. Furthermore, readily recycling and reusability can be achieved for the photocatalytic setup of CSA@g-C3N4 ascribed to its heterogeneous nature with no drop in the photoactivity.

Photocatalytic Regioselective Hydrofunctionalization of 1,4‐Diaryl‐1,3‐butadienes Using O‐, N‐, and C‐Nucleophiles

AbstractThe hydrofunctionalization of 1,3‐dienes is a challenging task especially with respect to controlling the regioselectivity of the corresponding adducts. Although various hydrofunctionalization approaches have already been developed, nucleophiles are often unselectively introduced at the C1‐ and C2‐positions of 1,3‐dienes. Here, we report a new methodology for the photocatalytic regioselective hydrofunctionalization of 1,4‐diaryl‐1,3‐butadienes in the presence of a photocatalyst under blue LED irradiation. O‐, N‐, and C‐nucleophiles are regioselectively introduced at the C1‐position of 1,4‐diaryl‐1,3‐butadienes to furnish the corresponding allylic (1,4‐adducts) and homoallylic (1,2‐adducts) derivatives as the major products. Moreover, the resultant mixture of 1,4‐adducts and 1,2‐adducts can be convergently transformed into a single reduced compound via hydrogenation.

Germination Characteristics and Seedling Growth of &amp;lt;italic&amp;gt;Pseudolysimachion nakaianum&amp;lt;/italic&amp;gt; (Ohwi) T. Yamaz. Seeds According to Light Quality Type

Background and objective: This study was conducted to understand the effect of different quality of light-emitting diodes (LED) on the germination characteristics and growth of &lt;i&gt;Pseudolysimachion nakaianum&lt;/i&gt;.Methods: The LED light irradiation was divided into white, red, blue, and red:blue (1:1). To investigate the germination characteristics, 30 seeds were placed in a Petri dish in three replicates for 8 days. Average germination rate, germination speed, germination uniformity, and average germination time were measured. To investigate the growth of seedlings, plant height, plant width, leaf length, leaf width, leaf number, fresh weight, dry weight and T/R ratio were examined 6 weeks after sowing, and chlorophyll fluorescence (maximum quantum yield, electron transport rate) was measured.Results: The final germination rate and germination speed were highest at red:blue (1:1) LED irradiation. Regarding growth and chlorophyll fluorescence measurements, red:blue LED showed the best growth results, with no significant difference in Fv/Fm between different types of light quality, and the electron transport rate was the highest under red:blue LED irradiation. Also, total fresh/dry weight and T/R ratio were highest for red:blue LED, it is presumed to promote the biomass of entire plant.Conclusion: The results proved that &lt;i&gt;Pseudolysimachion nakaianum&lt;/i&gt; showed red LED conditions promoted germination, but cultivation under red:blue LED conditions is judged to be suitable for seedling growth and photosynthesis.

Blue Light-Emitting Diode Irradiation Without a Photosensitizer Alters Oral Microbiome Composition of Ligature-Induced Periodontitis in Mice.

Objective: This study investigated the suppressive effects of blue light-emitting diode (LED) irradiation on bone resorption and changes in the oral microbiome of mice with ligature-induced periodontitis. Background: Wavelength of blue light has antimicrobial effects; however, whether blue LED irradiation alone inhibits the progression of periodontitis remains unclear. Methods: Nine-week-old male mice ligated ligature around the right maxillary second molar was divided into ligation alone (Li) and ligation with blue LED irradiation (LiBL) groups. The LiBL group underwent blue LED (wavelength, 455 nm) irradiation four times in a week at 150 mW/cm2 without a photosensitizer on the gingival tissue around the ligated tooth at a distance of 5 mm for 5 min. The total energy density per day was 45 J/cm2. Bone resorption was evaluated using micro-computed tomography at 8 days. Differences in the oral microbiome composition of the collected ligatures between the Li and LiBL groups were analyzed using next-generation sequencing based on the 16S rRNA gene from the ligatures. Results: Blue LED irradiation did not suppress bone resorption caused by ligature-induced periodontitis. However, in the LiBL group, the α-diversity, number of observed features, and Chao1 were significantly decreased. The relative abundances in phylum Myxococcota and Bacteroidota were underrepresented, and the genera Staphylococcus, Lactococcus, and Lactobacillus were significantly overrepresented by blue LED exposure. Metagenomic function prediction indicated an increase in the downregulated pathways related to microbial energy metabolism after irradiation. The co-occurrence network was altered to a simpler structure in the LiBL group, and the number of core genera decreased. Conclusions: Blue LED irradiation altered the composition and network of the oral microbiome of ligature-induced periodontitis in mice.

Short Oligo(dA) and Oligo(dC) Mediated Synthesis of Anisotropic Silver Nanoparticles under Blue LED Light Activation

Background: Synthesis of spherical silver nanoparticles is mostly reported, but the use of DNA, especially short oligonucleotides, to mediate the production of anisotropic AgNPs is still questioned. Objective: This work aims to use 30-mer oligo(dA) and oligo(dC) (or A30 and C30) to assist the formation of anisotropic AgNPs under blue LED irradiation. Method: We reported a simple synthesis reaction containing AgNO3, A30 (or C30), and sodium borohydride, which were exposed to 460 nm LED light for 24 h. The obtained AgNPs were characterized and assayed for antioxidant and antibacterial activities. Results: With exposure to 460 nm LED light, A30 and C30 could mediate the transition from spherical to hexagonal shapes of AgNPs with average sizes of 16 − 18 nm. Analyses of X-ray diffraction and selected area electron diffraction indicated the face-centered cubic crystal structure of AgNPs. A30- and C30-AgNPs exhibited similar antioxidant activities; IC50 of 78.68 ± 0.83 and 73.91 ± 0.46 μg mL−1, respectively. They also possessed antibacterial activities against Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Scanning electron micrographs revealed surface pores and rupture of bacterial cells in response to AgNPs. Conclusion: Oligonucleotides of only 30 residues are shown to assist the generation of anisotropic AgNPs under activation of blue LED irradiation, in which the synthesized AgNPs still exhibited antioxidant and antibacterial activities, suggesting a simple method to synthesize non-spherical AgNPs using short-length DNA.

Transition-Metal-Free and Photocatalyst-Free Sulfenylation of Halopyrazolamines under Visible-Light Irradiation via Electron Donor–Acceptor Complexes

AbstractA new approach was developed for the thiolation of halogenated pyrazole-5-amines under blue LED irradiation in metal-free conditions. This efficient and practical approach enabled the generation of thiolated pyrazol-5-amine building blocks of medicinal significance. This straightforward technique permits photochemical thiolation by an electron donor–acceptor by two distinct processes; formation of a charge-transfer complex through a halogen bond or π–π interaction based on various halogenated pyrazolamines, depending on the HOMO–LUMO energy gap of the C–X bond. The reaction of halogenated pyrazol-5-amines with thiophenol derivatives proceeded in good to excellent yields. The formation of a π–π complex or halogen bonding between the halopyrazolamine and the thiolate anion was confirmed by UV/visible spectroscopy.

Organophotocatalyzed Synthesis of Vinyl‐SCF3 and Benzoyl‐SCF3 Using a New N‐(SCF3)(CF3)‐Shelf‐Stable Reagent

AbstractWe report the photocatalyzed C−SCF3 bond formation using a new shelf‐stable PhPh‐N‐(SCF3)(CF3) reagent I in combination with 4CzIPN as organophotocatalyst under blue LED irradiation. While the synthesis of vinyl‐SCF3 is performed in the presence of bromide salts as an activator of reagent I, the synthesis of trifluoromethylthioesters was undertaken using aldehydes as starting material in the presence of a hydrogen atom transfer catalyst (HAT). Preliminary mechanistic investigations including EPR spectroscopy and cyclic voltammetry analysis shed the light on the reaction mechanisms.

Visible-Light-Promoted α-Benzylation of N-Phenyl α-Amino Acids to α-Amino Phenylpropanoids.

A new method for the synthesis of α-amino phenylpropanoids under blue light-emitting diode irradiation has been developed through α-C-H benzylation of readily available N-phenyl glycine ester with benzyl oxalates as a coupling partner under mild conditions. A range of N-phenyl glycine esters were successfully converted to α-amino phenylpropanoid products in moderate to good yields. The utility of this methodology is underlined by its application to the late-state modification of natural products.

Visible-Light-Induced Metal- and Photocatalyst-Free Radical Cascade Cyclization of Cinnamamides for Synthesis of Functionalized Dihydroquinolinones.

Visible-light-promoted metal- and photocatalyst-free radical cascade cyclization of cinnamamides with α-oxocarboxylic acids is described for sustainable synthesis of diverse pharmaceutically important dihydroquinolinone scaffolds in one pot under mild conditions. The decarboxylative cascade cyclization proceeded efficiently at room temperature without the need for expensive photocatalysts such as Ir or Ru complexes, which indicates the practicability and environmentally benign nature of this protocol. Preliminary mechanistic studies reveal that the blue LED irradiation efficiently cleaves the I-O bond of the hypervalent iodine reagent PhI(O2CCOAr)2 formed through ligand exchange between iodobenzene diacetate and arylglyoxylic acid to initiate the cascade reaction. The synthetic value of this operationally simple and energy-efficient method is further demonstrated by late-stage functionalization of drug molecules in excellent yields.

Blue light photocatalytic oxidation of sulfides to sulfoxides with oxygen over a thiazole-linked 2D covalent organic framework

With permanent porosity and intrinsic crystallinity, covalent organic frameworks (COFs) have great potential for solar energy conversions. However, the crystallinity of COFs necessitates reversible linkages like imine, leading to inadequate chemical stability of COFs as photocatalysts. To overcome this inadequacy, post-synthetic modifications (PSMs) transform an imine-linked COF, TTI-COF, into a thiazole-linked COF, TTT-COF. The morphology and crystallinity of TTT-COF are similar to that of TTI-COF. Compared to TTI-COF, TTT-COF secures evident amelioration of stability and optoelectronic properties supported by both experiments and theoretical calculations. Consequently, these two COFs are exploited for the photocatalytic oxidation of organic sulfides. Under blue light-emitting diode irradiation, TTI-COF marginally impels the reaction. In contrast, TTT-COF emerges with significantly better activity for selective oxidation of organic sulfides with oxygen in ethanol. This work sheds light on the transformative power of PSMs for tailoring COFs in visible light photocatalysis for oxidations.