ChemPhotoChem最新文献

A series of diphenylboron and 9-borafluoren-9-yl complexes with chiral Schiff-base ligands was synthesized and characterized by NMR spectroscopy. X-ray diffraction analysis revealed that their boron centers were adapted to tetrahedral coordination geometry. Although boron complexes with salicylideneimine backbones exhibited a weak circularly polarized luminescence (CPL), the CPL brightness (B_CPL) was enhanced more than 9-fold by the π-extension of the Schiff base ligands. Time-resolved emission decay analysis and theoretical calculations based on density functional theory (DFT) were conducted to further understand their luminescent properties.

Visible-light induced, photoredox catalysis has opened a wide range in the transformation of organic compounds in recent times. In synthetic organic chemistry HAT (hydrogen atom transfer) and SET (single electron transfer) mechanisms are a very noteworthy routes that has opened a window in favor of C−C single bond formations. Usually, a major role of unsaturated hydrocarbons is to participate in carbon-carbon bond formation as they carry reactive π-bond. Under visible-light, metal-free cross-coupling reactions are particularly favorable because of their atom economy, increased efficiency, and environmentally friendly procedures that result in the construction of C−C bonds. The review emphasizes the latest advancements of visible-light mediated, cross-coupling reactions of unsaturated hydrocarbons in metal-free conditions for constructing carbon-carbon single bonds.

The synthesis of diketopyrrolopyrrole (DPP) derivatives followed the well-known conventional cross-coupling methods such as Suzuki, Stille, Sonogashira, and Negishi cross-coupling reactions. However, these methods required unfavorable reaction conditions, organometallic precursors, and high temperatures. In addition, the synthesis of conventional cross-coupling partners including organoboranes, stannane, and acetylenes required drastic reaction conditions and strong bases. In this work, a wide variety of thiophene-diketopyrrolopyrrole (TDPP)-based semiconducting materials (36 compounds) were synthesized via Pd-catalysed photoredox methodology by using N-hydroxyphthalimide (NHP) based coupling partners, which can be readily prepared from N-hydroxyphthalimide and carboxylic acid or aldehyde derivatives via single step C−O bond formation reactions with good yield (80–90 %). This methodology minimizes additional synthetic steps, harsh reaction conditions, and high temperature (100–150 °C). Optoelectronic studies suggest that the synthesized materials have suitable band gap, HOMO and LUMO levels for variety of optoelectronic applications. To the best of our knowledge, this is the first report on the synthesis of TDPP-based π-conjugated materials via the photoredox method.

Using visible light conditions, we have developed a green protocol to prepare copper oxide-doped graphitic carbon nitride (Cu₂O@g-C₃N₄) photocatalysts with varied ratios of g-C₃N₄ nanosheets to copper oxide-dopant (0.1 %, 0.5 %, 0.7 %, and 5 % respectively) and characterized through various physicochemical techniques. These photo-responsive catalysts were used for the 1,4 radical oxidative addition of trans crotonaldehyde into β-hydroxybutyric acid (BA) as a major product, utilizing 30 % hydrogen peroxide as an oxidant and a white LED (Light Emitting Diode) source. Under the innoculous eco-friendly stipulations, Cu₂O@g-C₃N₄ (5 %) exclusively promoted the aforementioned reaction leading to 99.85 % trans crotonaldehyde conversion with 66.57 %, 24.1 %, and 9.1 % selectivity for β-hydroxybutyric acid, crotonic acid and subsequent radical synthesis, respectively.

Thermally activated delayed fluorescence (TADF) materials have attracted considerable interest due to their ability to enhance electrochemiluminescence (ECL). This is achieved through the efficient upconversion of triplet excitons and the subsequent radiative transitions. However, despite the potential of TADF materials, there have been few studies exploring their application in ECL field. Accordingly, in this concept, a number of TADF materials, which can be categorized into two principal groups based on intramolecular bond charge transfer and intermolecular space charge transfer, are introduced in order to explore the potential for their application in ECL. A brief review of their properties not only helps to deepen the understanding of the nature of TADF materials, but also provides basic guidance and support for the introduction of the TADF mechanism into ECL systems, with the aim of enhancing the luminescence efficiency of ECL.

Carbon dioxide (CO₂) is the primary greenhouse gas responsible for global warming, posing a significant challenge to the global environment. To reduce CO₂ emission and support the sustainable development, efficient conversion of CO₂ into chemical feedstocks has gained a lot of attention. One promising strategy inspired by natural photosynthesis is solar-driven CO₂ reduction, which uses appropriate photocatalytic systems to generate CO, HCOOH, CH₄, CH₃OH, etc. However, developing low-cost, environmentally friendly, and non-toxic materials for the catalytic conversion of CO₂ remains a significant challenge. Light-absorbing photosensitizers play an important role in photocatalytic systems. Recently, non-precious metal photosensitizers such as organic compounds and earth-abundant metal complexes have been intensively studied for developing low-cost photocatalytic systems. This review focuses on recent reports on organic and non-precious metal photosensitizers for photocatalytic CO₂ reduction.

The fluorescent probe provides a simple for detecting Cu²⁺ through fluorescence quenching of the Schiff-base probes by Cu²⁺. However, the azine-based probes often suffer from poor solubility and dispersibility in water and are easily interfered with by other competing ions, which significantly reduces their applicable potential. In this study, we synthesized a water-dissoluble and highly fluorescent γ-Cyclodextrin (γ-CD)/2-hydroxybenzaldehyde azine (2-HBA) inclusion complex for Cu²⁺ detection. The inclusion of 2-HBA into γ-CD enhances its solubility in water and allows it to emit fluorescence. The as-synthesized γ-CD/2-HBA probe exhibits high sensitivity for colorimetric and fluorescent detection of Cu²⁺, with detection limits reaching 2.72 and 1.53 nM, respectively. The results exceed most of those reported in the literature. The probe's structure and potential mechanism were systematically analysed using the experimental and theoretical methods.

Pyrimidines, a prominent isomer class of diazines, are promising molecular constituents of electron-deficient luminescent and hole-transport materials. Here, we report the fluorescence lifetimes and describe the electronic structures and character of low-lying emissive excited states of a series of synthetically accessible donor-acceptor-donor (D−A−D′) and donor-acceptor-acceptor (D−A−A′) type pyrimidines, including both all-organic and hybrid organic-organometallic analogues. We find that strategically varying the aryl substituents on a pyrimidine enables tuning of the character of the luminescent excited states from charge-transfer (CT) to locally excited (LE) states, which then differ in their sensitivity to their environment. This study suggests structural handles for controlling the photophysics of arylpyrimidines relevant to a variety of applications for luminescent materials.

Retraction: L. Biesen, T.J.J. Müller, “Aggregation-Induced Emission-Active Donor-Substituted Aroyl-S,N-Ketene Acetals via Nucleophilic Amine Base Attack”, ChemPhotoChem 2023, 7, e202300111, https://doi.org/10.1002/cptc.202300111.

The above article, published online on 25 August 2023 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors; the journal Editor-in-Chief, Deanne Nolan; Chemistry Europe; and Wiley-VCH GmbH. The retraction has been agreed at the request of the authors, who informed the editor of significant errors in the structural assignment of compounds 3a, 3c and 3e, in addition to instrumental error affecting solid state and aggregate quantum yield measurements. As a result, the conclusions reported in the article are not considered reliable.

A modular synthesis of novel series of 1,7-difluorinated BODIPYs has been elaborated. First, the acid-catalyzed condensation of ethyl 3-aryl-4-fluoro-1H-pyrrole-2-carboxylates with aromatic aldehydes gives the corresponding dipyrromethane-1,9-dicarboxylates. The latter are subjected to the exhaustive reduction with lithium aluminum hydride to transform the ester moieties into methyl groups. The subsequent oxidation of the resulting 1,9-dimethylated dipyrromethanes followed by the boron difluoride complexation afforded a family of novel core-fluorinated BODIPYs in up to 74 % yield. Photophysical properties of the resulting BODIPYs were tuned by varying of the starting fluoropyrroles and aromatic aldehydes and were studied by UV-visible and fluorescence spectroscopy. As a result, the fluorescence quantum yields of the obtained compounds reached up to 99 %. In addition, their ability to generate singlet oxygen and electrochemical properties were also evaluated. As a result, a new promising family of fluorophores with a good combination of the fluorescence and photosensitizing properties was obtained. It was found that conversion of ester groups into methyl ones at the 3,5-positions of the BODIPY core is a crucial step toward fluorescence enhancement. In addition, DFT calculations were performed to elucidate a relationship between electronic structure, geometry and photophysical properties of these BODIPYs.