The ellipsoidal geometry of the BODIPY-Ar-chol molecule results in a tri-exponential decay of anisotropy dynamics. The molecule‘s radius along the y-axis is 6.3 Å and fluid volume displaced by rotation along the y-axis is 11983.9 ų. The largest fluid volume displacement along the y-axis induces the largest rotational relaxation time of 440 ps. Rotational relaxation time along the x and z axes follow accordingly.

Abstract

BODIPY and BODIPY-derived systems are widely applied as fluorophores and as probes for viscosity detection in solvents and biological media. Their orientational and rotational dynamics in biological media are thus of vital mechanistic importance and extensively investigated. In this contribution, polarization-resolved confocal microscopy is used to determine the orientation of an amphiphilic BODIPY-cholesterol derivative in homogeneous giant unilamellar vesicles (GUV) made from 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC). The BODIPY-moiety of the molecule is placed near the polar headgroups, and the cholesterol moiety is embedded in the membrane along the acyl chain of the lipids. The rotational relaxation of fluorophore is conventionally investigated by time-resolved emission anisotropy (TEA); and this method is also used here. However, TEA depends on the emission of the fluorophore and may not be useful to probe rotational dynamics of the non-emissive triplet states. Thus, we employ femtosecond transient absorption anisotropy (TAA), that relies on the absorption of the molecule to complement the studies of the amphiphilic BODIPY in DCM and GUV. The photoinduced anisotropy of the BODIPY molecule in DCM decays tri-exponentially, the decay components (sub-5 ps, 43 ps and 440 ps) of anisotropy are associated with the non-spherical shape of the BODIPY molecule. However, the anisotropy decay in homogenous GUVs follows a biexponential decay; which arises from the wobbling-in-a-cone motion of the non-spherical molecule in the high viscous lipid bilayer media. The observations for the BODIPY-chol molecule in the GUV environment by TAA will extend to the investigation of non-emissive molecules in cellular environment since GUV structure and size resembles the membrane of a biological cell.

Oxygen-mediated surface photoreactions are an extremely versatile tool for environmental remediation, recycling of critical raw materials and sustainable production of feedstocks. This Concept reviews recent works on this class of reaction, including examples of metal and polymer recovery and recycling from waste, metal-free oxidation of organic molecules and exploitation of persistent radicals for destroying pollutants and disinfection.

Abstract

This Concept analyses and reviews recent works that take advantage of oxygen-mediated surface photoreactions for addressing key issues in the fields of sustainable chemistry, circular production of feedstocks and environmental remediation. Examples of metal and polymer recovery and recycling from waste, metal-free oxidation of organic molecules and exploitation of persistent radicals for destroying pollutants and disinfection are discussed, highlighting common aspects, peculiarities, potential and limitations.

The relationship between molecular structure and photophysical properties of a range of boron-based TADF molecules were investigated to provide a clear approach to the structure-performance relation. Torsion angles, excited state energy alignments, singlet-triplet energy gaps, particle-hole orbital overlap extent and spin orbit coupling for reverse intersystem crossing processes were utilized.

Abstract

Thermally activated delayed fluorescence (TADF) materials have shown great potential in the design of organic metal-free optoelectronic devices and materials and, therefore, are the subject of intense investigations. This contribution presents the effects of various parameters on the photophysical properties of a series of boron-based TADF emitters. These include torsion angle, the changes in the electronic density, energy gap between the first excited singlet (S₁) and the first excited triplet states (T₁), oscillator strength (f) and spin-orbit coupling (SOC). Through a comprehensive structural analysis, we first show the most favorable conformation of the ground state of donor (D) and acceptor (A) moieties that are popular in TADF emitters. Further, the properties of the excited state manifolds are obtained with Tamm-Dancoff Approximation (TDA), thus rationalizing their optical and photophysical properties. Globally, our results settle the basis for the rationalization of the effects of different parameters on reverse intersystem crossing (RISC) probabilities, which is the rate-limiting step for TADF, thus favoring the rational design of novel highly efficient TADF materials with strong triplet exciton harvesting.

Herein, we report on a tri-component photochromic molecular cocktail that can be used to encrypt and decrypt information. The time-dependent fluorescent response of this cocktail is highly non-linear with respect to the set of inputs used (concentrations of the three photochromic components, excitation- and emission wavelengths), a property required for the generation of so-called encryption keys. The all-optical system can generate more than 8 million unique fluorescence responses by applying different input combinations and is operated using a conventional fluorimeter.

Heterogeneous photocatalysis can increase the sustainability of photochemistry by providing simple means for catalyst recovery and reuse. This review explores four prevalent classes of these materials: Photocatalytic Nanoparticles, polymer networks, metal organic frameworks (MOFs), and immobilized photocatalysts on solid supports in their use for light-mediated reversible deactivation radical polymerization.

Abstract

Heterogeneous photocatalysis combines the benefits of light-mediated chemistry with that of a catalytic platform that facilitates re-use of (often expensive) photocatalysts. This provides significant opportunities towards more economical, sustainable, safe, and user-friendly chemical syntheses of both small and macromolecular compounds. This contribution outlines recent developments in the design of heterogenous photocatalysts and their use to mediate polymerizations. We outline four classes of heterogeneous photocatalysts in detail: Nanoparticles, conjugated and non-conjugated polymer networks, metal-organic frameworks (MOFs), and functionalized solid supports.

The combination of photoinduced hydrogen atom transfer (HAT) and cobalt catalysis gives access to a mild dehydroformylation sequence for the defunctionalization of benzyl alcohols to arenes. The transformation proceeds through a stepwise radical pathway, wherein benzylic and acyl radicals are generated as key intermediates. As a result, stable C−C bonds can be cleaved while generating concomitant syngas (CO+H₂).

Abstract

In the last decades, many C−C bond-forming reactions have been developed, whereas less attention has been paid to the design of strategies involving C−C bond cleavage. We report a photocatalytic dehydroformylation sequence for the conversion of benzyl alcohols to arenes in a one-pot two-step process. Herein, the initial dehydrogenation of the benzyl alcohols to the corresponding benzaldehydes is combined with an additional decarbonylation step yielding arenes. As a result, a broad range of benzyl alcohols can be easily transformed in short times under mild photocatalytic conditions. The conducted mechanistic studies indicate that our cooperative hydrogen atom transfer (HAT)-cobalt system proceeds through the formation of α-alkoxy- and acyl radicals as key intermediates, involving concomitant syngas (CO+H₂) generation.

Chrysanthemum-like BiOBr microspheres (CLB_0.45) were designed and prepared by using chitosan (CS) as a soft template/structure inducer. CLB_0.45 demonstrated efficient performance for the degradation of organic pollutants (dyes and antibiotics) due to suitable lattice plane exposure and band gap. The material also exhibited good cyclic stability.

Abstract

Photocatalysis is a green technology with important application prospects in environmental fields such as wastewater treatment. Herein, we synthesized chrysanthemum-like BiOBr microspheres (CLB_0.45) by introduction of structure guide and soft-template. Natural biomass chitosan (CS) in the precursor of BiOBr successfully suppressed the growth of both (001) and (102) lattice planes through the solvent effect, and promoted the exposure of (110) lattice planes that dominated the photocatalytic performance. Significantly, the polymer chains regulated the nanosheets of BiOBr to accurately self-assemble. The obtained CLB_0.45 had narrower band gap and more active sites due to surface defects, and the photocatalysts have higher photo-electron hole pairs separation efficiency. Additionally, the degradation performance towards rhodamine B (RhB; 99.7 %, 30 min) of the CLB_0.45 was increased, which was 4.6 times higher than that of pure BiOBr. The degradation rate of tetracycline (TC) was also excellent (85.3 %). The photodegradation mechanism of CLB_0.45 was proposed and verified. In summary, the prepared CLB_0.45, obtained through structure guiding and using a soft template, have a promising future in the photocatalytic purification of organic pollutants.

Let's see… Recent advances in the development and application of supramolecular luminescent nano-assemblies based on different functional building blocks in cell imaging are reviewed. These supramolecular luminescent nano-assemblies have wide applications in targeted imaging of specific organelles, drug delivery, and therapy.

Abstract

Supramolecular luminescent nano-assemblies for cell imaging have recently attracted increasing interest, not only because of their outstanding photophysical properties, but also because of their easy fabrication through supramolecular strategies, good biocompatibility, high stability to photo- and micro-environments in cells, and facile combination of imaging and synergistic therapy for cancers. Luminescence-based bioimaging has great advantages, such as high sensitivity, being non-invasive, and functioning in real-time, leading to its wide application in many fields, including disease research, drug research, cell markers, gene expression, gene function studies, and protein interaction. In this Review, recent progress in the application of macrocycle-mediated (e.g., cyclodextrins, cucurbiturils, calixarenes, and pillar[n]arenes) and functionalized amphiphilic molecule-based supramolecular luminescent nanoparticles in cell imaging, especially targeted cell imaging of specific organelles, is reviewed. The combination of imaging with drug delivery, gene delivery, and photodynamic therapy is also introduced.

The Front Cover shows various luminescent nano-assemblies flying into cells and lighting them for cell imaging. Non-covalent interaction and binding enable the formation of dynamic supramolecular self-assemblies, realizing in situ control of luminescence and loading capacity for diagnosis, drug delivery, and treatment. More information can be found in the Review Article by Xu-Man Chen, Quan Li and co-workers.

A photo-induced transformation, specific to the nanometric size and different from the well-documented photo-induced electron transfer in molecules and large size coordination polymers, is evidenced in 5 nm nanocrystals of an alkali cation free CoFe Prussian blue analog by SQUID magnetometry and X-ray absorption spectroscopy.

Abstract

The discovery of a photomagnetic effect in a CoFe Prussian blue analog (PBA) has triggered a growing interest for photo-switchable bimetallic cyanide-bridged systems. Nevertheless, in between cyanide-bridged extended coordination polymers and discrete molecules, the photo-switching phenomena are much less well known in nano-sized materials. A photo-induced transformation, specific to the nanometric size, is evidenced by magnetometry and by X-ray absorption spectroscopy at the Co and Fe K-edges in an alkali cation free Prussian blue analog. The nanoparticles before irradiation can be described as having a core-shell structure, the core being made of the well-known fcc-Co^II(HS)Fe^III structure of CoFe PBAs while the shell contains Co^II ions in octahedral geometry and significantly distorted Fe(CN)₆ entities. Irradiation induces a change of the local structures around the transition metal ions, which remain in the same oxidation state, with different behaviors of the Co and Fe sub-lattices.