ChemPhotoChem最新文献

The photophysical properties of a series of thermally activated delayed fluorescence emitters, comprising a nitrogen-based donor, a phenylene bridge and a boron-based acceptor, are investigated using a combination of density functional theory and multi-reference configuration interaction methods. In addition to singlet and triplet charge-transfer (CT) states, an acceptor-localized low-lying triplet state is found in all compounds. The size of the singlet–triplet gap and the energetic order of the CT and locally excited (LE) states can be modulated by regioisomerism (ortho- or para-linkage) and the chemical modification of the subunits. Spin-vibronic interactions, introduced through a Herzberg–Teller-type approach, are found to accelerate the intersystem crossing process considerably provided that the CT and LE states are close in energy.

Chemical modification of nucleic acids (oligonucleotide, DNA, and RNA) is a powerful tool, widely used in chemical biology. There is a growing interest in light-mediated nucleic acid modification within biological systems, driven by the exceptional spatiotemporal precision that light offers. Moreover, light-induced chemical modification of nucleic acids, utilizing light as an external energy source, offers a powerful and efficient alternative to conventional labor-intensive de novo synthesis. In this regard, visible light exhibits a highly efficient and selective approach, enabling precise labeling of target sites without compromising their structural integrity, while high-energy UV light triggers detrimental photochemical reactions, causing DNA/RNA damage. Light-mediated selective labeling and interstrand crosslinking of DNA/RNA duplexes hold great potential for applications in DNA repair, gene regulation, and nanotechnology. Photouncaging and photoswitching enable precise control over biological processes like transcription, RNA interference, and translation. Moreover, light-mediated DNA-encoded libraries provide a sustainable and efficient method for generating vast small-molecule libraries, valuable for pharmaceutical discovery. This review highlights recent advancements in light-mediated nucleic acid modifications, including labeling, crosslinking, photouncaging, photoswitching, and DNA-encoded library synthesis, accompanied by comprehensive discussion and analysis.

The Front Cover illustrates the light emission of the Pt(II) complex aggregate in a biological environment upon irradiation with near infrared (NIR) II laser light. The laser light can reach the deep tissue though the NIR II optical window, where the light scattering and absorption by water molecules and hemoglobin are suppressed, and directly excite the Pt(II) complex aggregate to operate as a photosensitizer in phototherapy and as a luminophore to play a role of a photoimaging agent. More information can be found in the Review Article by Shingo Hattori and Kazuteru Shinozaki (DOI: 10.1002/cptc.202500041).

Upconversion nanocrystals (UCNC) as energy converters have garnered significant attention due to their exceptional luminescent properties. However, the limited performance capabilities of single UCNC fail to meet the demands of increasing application–oriented research. To integrate multiple functionalities, UCNC–based heterostructures have been explored. These heterostructures, comprising UCNC and other functional components (transition metals, semiconductors, quantum dots, metal–organic frameworks, SiO₂, etc.), present an intriguing system in which the morphology and physicochemical properties are significantly influenced by the combination of functional units. As multifunctional hybrid architectures, UCNC–based heterostructures surmount the intrinsic limitations of individual UCNC configurations, exhibiting synergistically enhanced properties. Nevertheless, due to the chemical composition discrepancy and large lattice mismatches, the synthesis of UCNC–based heterostructures remains challenging. To date, most UCNC–based heterostructures have been fabricated through nonepitaxial growth methods, while epitaxial growth connections remain relatively limited. In this review, recent advancements in the field of UCNC–based heterostructures are summarized and trends in their biomedical applications are outlined. Finally, the challenges and potential opportunities in this field are discussed.

Achieving multicolor emissions from a single molecule has been an active field of research, particularly in developing organic light-emitting diodes. Reported herein is acenaphthylenedione (AcD), which displays multiple colors as a function of excitation wavelengths. Experimental and theoretical data reveal that the latter emits strongly from S₃ and weakly from S₂, while S₁ remains as a dark state, thus violating Kasha's rule. The calculated large energy difference between S₂ and S₃ (i.e., 1.00 eV) promotes radiative decay from S₃ rather than internal conversion (IC) to S₁. Hydrazones derived from the same also possess excitation wavelength-dependent emission. Time-dependent density functional theory (TDDFT) calculations reveal that the longer wavelength emission can be assigned to enol-form, produced through excited-state intramolecular proton transfer (ESIPT) and locally excited (LE) keto-form, while that of the shorter wavelength to LE S₂, thus disobeying Kasha's rule. The calculated energy difference (ΔE_S1-S2) is found to be 0.64 eV, which reduces the rate of IC (i.e., S₂ → S₁), resulting in the emission from the higher excited state. N-methylated hydrazone, which blocks the ESIPT channel, also supports the hypothesis. Furthermore, all the compounds exhibit aggregation-induced emission behavior, and nitro- and cyano-substituted hydrazones are found as good candidates for antibacterial, antioxidant, and anticancer activities.

The photochemistry of resveratrol with singlet oxygen (¹O₂) under blue-LED irradiation is explored in the presence of three metal-free porphyrins as photosensitizers. Irradiation at 450 nm yields products of CC bond scission, 6-electron electrocyclic ring closure, and [4 + 2] cycloaddition, including benzaldehydes, 2,4,6-trihydroxyphenanthrene, and resveratrol cyclic endoperoxide. The selectivity of the process is controlled by the structure of the metal-free porphyrin and by the nominal capacity of the blue-LED photon. The scope of the reaction is extended to sustainable heterogeneous photosensitizers produced by immobilization of metal-free porphyrins on lignin, the most abundant polyphenol in nature characterized by beneficial photochemical properties.

Herein, how aggregation-dispersion behavior of fluorinated azobenzene derivatives 5 and 6 with an amphiphilic dodecaoctane substituent is affected by UV light irradiation and water is described. The influence of fluorine substituents on their photophysical properties, photoswitching differences, and aggregation in waterin-ground trans and excited cis-state is studied. Their photophysical and photoswitching properties are investigated under the polar MeOH and nonpolar solvent benzene and it is found that 6 shows different behavior as compared to 5 in both solvents. Further, to check their aggregation properties in MeOH, a competing solvent water is added. It is observed that in MeOH–H₂O solution (0.9-1.5 mL), compounds show a redshift with a decrease in the absorbance, and fluorescence emission is found. Further, dynamic light scattering shows the opposite behavior, 5 initially is in the macromolecular aggregated state both in trans and cis-states but the addition of water disperses the solution. However, 6 shows uniform micromolecular aggregated features in the trans-state and disperses further after the addition of water. Scanning electron microscopy images of 5 and 6 suggest aggregated patterns that change the morphology when added to water. IR, ¹H, and ¹⁹F NMR are done to understand the site of aggregation and intermolecular interactions.

Over the past decades, visible-light-driven reactions have emerged as a powerful tool in organic synthesis. Unlike traditional photoredox reactions that require additional catalysts or photosensitizers, electron donor–acceptor (EDA) complex-mediated photochemistry offers a simpler and more cost-effective approach to achieving diverse radical transformations without the need for noble catalysts. Among these, the use of boron-containing compounds as electron donors or acceptors in EDA complexes has garnered significant attention due to their unique properties. This review highlights recent advances in visible-light-induced EDA complex-mediated transformations involving boron-containing compounds, focusing on their applications in constructing CC and CB bonds and elucidating the underlying reaction mechanisms.

Organic nonlinear optical (NLO) materials with strong light-responsive properties have garnered significant attention in the field of optoelectronics due to their chemical tunability and cost-effective synthesis. Enhancing the NLO performance of these materials is essential to meet the growing demands in applications such as optical modulation and communication. Interestingly, twisted structures have been shown to alter NLO properties, offering a novel design approach. This review systematically examines recent advances in twisted D-π-A type organic chromophores for enhancing NLO performance, with a particular focus on the key mechanisms of molecular structure design and performance optimization. It provides a detailed discussion of the design strategies aimed at improving the NLO performance of twisted organic chromophores, highlighting the significance of twisted structures and electronic group design. The literature review indicates that optimizing twist angles, strengthening donor and acceptor group intensities, and optimizing π-conjugated bridges are effective ways to enhance NLO performance.

This study focuses on the impact of alternant phenyl substituents on the photophysical properties of tris-(2,4,6-trichlorophenyl)methyl (TTM)-type radicals. Most donor–acceptor-type luminescent systems show solvent-polarity sensitivity, which limits their applications. Herein, three alternate π-conjugated biphenyl/terphenyl substituents are attached to the TTM unit. Results reveal that connection modes and types of benzene ring derivatives lead to distinct charge transfer (CT) and locally excited state hybrid emitters due to the differences in conjugation degree. All three radicals exhibit polarity-insensitive red emission (626–690 nm), and their photoluminescence quantum yields (PLQYs) increase with solvent polarity. Specifically, linear-conjugated TTM-DPh has higher photostability but lower PLQY, while nonlinear-conjugated TTM-3DPh and TTM-TPh have nearly 10-fold higher PLQYs. The photophysical studies suggest that the conjugation degree and hybridization level between CT and ground states account for these properties.