Green approach for the fabrication of a ternary nanocatalyst (Ag-ZnONPs@Cy) for visible light-induced photocatalytic reduction of nitroarenes to aminoarenes

In recent times, the incorporation of metal oxide nanoparticles with organic dyes has piqued the interest of numerous researchers due to their diverse applications under visible light instead of UV radiation. This investigation employed a three-step methodology to fabricate cyanidin-sensitized silver-doped zinc oxide nanoparticles (Ag-ZnO@Cy). Initially, cyanidin dye was extracted from fresh black mulberry fruit, followed by the eco-friendly synthesis of Ag-ZnO nanoparticles (Ag-ZnONPs). The successful integration of the prepared cyanidin dye with Ag-ZnONPs was achieved through a straightforward, environmentally benign, and cost-efficient procedure. The resultant ternary composite underwent comprehensive characterization and confirmation utilizing various techniques, such as SEM, FT-IR, EDX, DRS, elemental mapping, and XRD. The experimental results for Ag-ZnONPs@Cy demonstrated that the nanocrystalline wurtzite exhibited spherical shapes with an average crystal size of 27.42 nm. Moreover, the photocatalytic activity of the synthesized Ag-ZnONPs@Cy was meticulously investigated under blue LED light irradiation. This inquiry encompassed examinations of catalyst amount, regeneration, stability, reusability, and the influence of light source on the hydrogenation of nitroarenes to the corresponding aminoarenes. The findings shed light on the potential of this composite for diverse photocatalytic applications.

Aerobic Oxidative EDA Catalysis: Synthesis of Tetrahydroquinolines Using an Organocatalytic EDA Active Acceptor

A catalytic electron donor-acceptor (EDA) complex for the visible-light-driven annulation reaction between activated alkenes and N,N-substituted dialkyl anilines is reported. The key photoactive complex is formed in situ between dialkylated anilines as donors and 1,2-dibenzoylethylene as a catalytic acceptor. The catalytic acceptor is regenerated by aerobic oxidation. Investigations into the mechanism are provided, revealing a rare example of a catalytic acceptor in photoactive EDA complexes that can give access to selective functionalization of aromatic amines under mild photochemical conditions.

A thiadiazolopyridine-functionalized Zr(iv)-based metal-organic framework for enhanced photocatalytic synthesis of tetrahydroquinolines under visible light

Metal–organic framework (MOF) materials provide a versatile and promising platform for constructing heterogeneous photocatalysts with applications in organic transformations. One of the methods for enhancing MOFs' performance in photocatalysis relies on the elaborate design and functionalization of organic linkers. Here we reported a photoactive thiadiazolopyridine (TDP) moiety functionalized UiO-68 isoreticular Zr(iv)-based MOF (denoted as UiO-68-TDP) that was synthesized by the de novo approach of mixed dicarboxylate struts. Under blue LED irradiation and in an open air atmosphere, MOF UiO-68-TDP exhibited a largely higher photocatalytic activity for the synthesis of tetrahydroquinolines by oxidative annulation reaction between N,N-dimethylanilines and maleimides, in comparison to the benzothiadiazole decorated analogue MOF. Besides, UiO-68-TDP can be reused at least three times without significant loss of its photocatalytic activity and its framework was well maintained after these cycles. Furthermore, the related mechanism involving reactive oxygen species was properly proposed.

A photoactive thiadiazolopyridine moiety functionalized UiO-68 isoreticular MOF exhibited an enhanced photocatalytic activity for the synthesis of tetrahydroquinolines between N,N-dimethylanilines and maleimides under visible light.

Progress on photocatalytic semiconductor hybrids for bacterial inactivation

Due to its use of green and renewable energy and negligible bacterial resistance, photocatalytic bacterial inactivation is to be considered a promising sterilization process. Herein, we explore the relevant mechanisms of the photoinduced process on the active sites of semiconductors with an emphasis on the active sites of semiconductors, the photoexcited electron transfer, ROS-induced toxicity and interactions between semiconductors and bacteria. Pristine semiconductors such as metal oxides (TiO₂ and ZnO) have been widely reported; however, they suffer some drawbacks such as narrow optical response and high photogenerated carrier recombination. Herein, some typical modification strategies will be discussed including noble metal doping, ion doping, hybrid heterojunctions and dye sensitization. Besides, the biosafety and biocompatibility issues of semiconductor materials are also considered for the evaluation of their potential for further biomedical applications. Furthermore, 2D materials have become promising candidates in recent years due to their wide optical response to NIR light, superior antibacterial activity and favorable biocompatibility. Besides, the current research limitations and challenges are illustrated to introduce the appealing directions and design considerations for the future development of photocatalytic semiconductors for antibacterial applications.

Visible-light-mediated phosphonylation reaction: formation of phosphonates from alkyl/arylhydrazines and trialkylphosphites using zinc phthalocyanine

In this work, we developed a ligand- and base-free visible-light-mediated protocol for the photoredox syntheses of arylphosphonates and, for the first time, alkyl phosphonates. Zinc phthalocyanine-photocatalyzed Csp2-P and Csp3-P bond formations were efficiently achieved by reacting aryl/alkylhydrazines with trialkylphosphites in the presence of air serving as an abundant oxidant. The reaction conditions tolerated a wide variety of functional groups.

Boron-doped TiO2 (B-TiO2): visible-light photocatalytic difunctionalization of alkenes and alkynes

Boron-doped TiO₂ (B-TiO₂) was prepared, characterized, and applied as a reusable, inexpensive, and available heterogeneous nanophotocatalyst under visible light for the synthesis of phenacyl thiocyanates.

Photosensitive Hybrid Nanostructured Materials: The Big Challenges for Sunlight Capture

Solar radiation is becoming increasingly appreciated because of its influence on living matter and the feasibility of its application for a variety of purposes. It is an available and everlasting natural source of energy, rapidly gaining ground as a supplement and alternative to the nonrenewable energy feedstock. Actually, an increasing interest is involved in the development of efficient materials as the core of photocatalytic and photothermal processes, allowing solar energy harvesting and conversion for many technological applications, including hydrogen production, CO2 reduction, pollutants degradation, as well as organic syntheses. Particularly, photosensitive nanostructured hybrid materials synthesized coupling inorganic semiconductors with organic compounds, and polymers or carbon-based materials are attracting ever-growing research attention since their peculiar properties overcome several limitations of photocatalytic semiconductors through different approaches, including dye or charge transfer complex sensitization and heterostructures formation. The aim of this review was to describe the most promising recent advances in the field of hybrid nanostructured materials for sunlight capture and solar energy exploitation by photocatalytic processes. Beside diverse materials based on metal oxide semiconductors, emerging photoactive systems, such as metal-organic frameworks (MOFs) and hybrid perovskites, were discussed. Finally, future research opportunities and challenges associated with the design and development of highly efficient and cost-effective photosensitive nanomaterials for technological claims were outlined.

ARS–TiO2 photocatalyzed direct functionalization of sp2 C–H bonds toward thiocyanation and cyclization reactions under visible light

An ARS–TiO₂ photocatalyst has been prepared, by a simple method through stirring a mixture of ARS and TiO₂ at room temperature in the dark, to extend the photocatalytic response of titanium dioxide toward the visible light spectrum.

Black TiO2 nanoparticles with efficient photocatalytic activity under visible light at low temperature: regioselective C–N bond cleavage toward the synthesis of thioureas, sulfonamides, and propargylamines

Several different colored forms of TiO₂ were prepared through the easy treatment of white TiO₂ and NaBH₄ as a safe hydrogen source. Then, tertiary amines were harnessed toward the regioselective synthesis of three prominent scaffolds.

Visible-light-driven photochemical activity of ternary Ag/AgBr/TiO2 nanotubes for oxidation C(sp3)–H and C(sp2)–H bonds

The Ag/AgBr/TiO₂ ternary nanotube as a heterogeneous photocatalyst was used for the solvent-free oxidation of the benzylic C(sp³)–H bond or the solvent-controlled selective oxidative cleavage of the CC double bond of styrene under visible light at room temperature.

Cercosporin-photocatalyzed sp3 (C-H) activation for the synthesis of pyrrolo[3,4-c]quinolones

We reported a new method that visible light along with cercosporin, one of the naturally occurring perylenequinonoid pigments with excellent properties of photosensitization, photocatalyzed sp³ (C-H) activation for the synthesis of pyrrolo[3,4-c]quinolones through the annulation of anilines and maleimides under mild conditions.

Enhancing the photo-efficacy of an organic visible-light-activated chromophore (alizarin red S) on zinc oxide with a Ag-Na electrolyte to photo-transform aromatic and aliphatic alcohols

The development of an aqueous silver-sodium/alizarin red sensitised zinc oxide system has been reported to oxidise a range of both aromatic and aliphatic alcohols to aldehydes. Furthermore, photoluminescence spectroscopy validated the electron quenching effect of zinc oxide's defect sites after surface sensitising the metal-oxide with alizarin red. Powder diffuse reflectance UV/Vis data further substantiated the visible-light attenuated properties of alizarin red sensitised zinc oxide, and hence justification for its visible light reactivity towards alcohol oxidations. Lastly, density functional theory calculations supported the intermolecular photo-electronic transfer between alizarin red organic and zinc oxide.

The toxic effects of alizarin red S on catalase at the molecular level

Alizarin red S (ARS) is a widespread mordant dye derived from alizarin. However, it was reported to be mutagenic and carcinogenic probably because it could induce oxidative damages in organisms. Catalase (CAT) is an important antioxidant enzyme defensing oxidative damages induced by xenobiotics. The underlying mechanisms of ARS interacting with CAT have not been clarified yet. This study is conducted to characterize the functional and conformational changes on CAT by ARS and the binding details to further investigate their interaction mechanisms. Under exposure of ARS at 5 μM, CAT activity was significantly decreased to 76.2%. Inhibition of CAT probably resulted in promotion of intracellular oxidative stress and pro-oxidant property of ARS. The interaction between ARS and CAT was proved to be spontaneous and exothermic. However, limited structural changes were observed according to spectroscopic results. Results showed that ARS prefers to bind with residues buried in the active site and could alter the activity of CAT, which were agree with the molecular docking results. This work proves the adverse effects of ARS on CAT mainly at molecular level and further highlights its potential risks to heath.

Alizarin red S is confirmed to be toxic to catalase at molecular level attributing to the structural and functional changes of catalase.

Structural elaboration of dicyanopyrazine: towards push–pull molecules with tailored photoredox activity

As an extension of the successful dicyanopyrazine photoredox catalysts, a series of X-shaped push–pull molecules with a systematically altered structure were designed and facilely synthesized; their structure–property relationship was elucidated in detail via experimental as well as theoretical calculations. Dicyanopyrazines are proven to be powerful photoredox catalysts with a push–pull arrangement that allows facile property tuning by interchanging a particular part of the D–π–A system. Changing the mutual position of the cyano acceptors and the methoxy, methylthio and thienyl donors as well as modifying the linker allowed wide tuning of the fundamental properties of the catalysts. Contrary to the currently available organic photoredox catalysts, we provided a series of catalysts based on a pyrazine heterocyclic scaffold with easy synthesis and further modification, diverse photoredox characteristics and wide application potential across modern photoredox transformations. The photoredox catalytic activities of the target catalysts were examined in a benchmark cross-dehydrogenative coupling and novel and challenging annulation reactions.

X-shaped push–pull molecules based on dicyanopyrazine were designed, synthesized and experimentally/theoretically investigated. They proved to be tunable photoredox catalysts in selected chemical transformations.

Recent advances in modified TiO2 for photo-induced organic synthesis

The recent advancements of modified TiO₂ materials as photocatalysts for organic synthesis are summarized.

Synthesis of pyrrolo[3,4-c]quinoline-1,3-diones: a sequential oxidative annulation followed by dehydrogenation and N-demethylation strategy

A synthetic strategy for pyrrolo[3,4-c]quinoline-1,3-diones via oxidative annulation followed by DDQ mediated dehydrogenation and N-demethylation.