Donor–Acceptor Fluorophores for Visible-Light-Promoted Organic Synthesis: Photoredox/Ni Dual Catalytic C(sp³)–C(sp²) Cross-Coupling

We describe carbazolyl dicyanobenzene (CDCB)-based donor–acceptor (D–A) fluorophores as a class of cheap, easily accessible, and efficient metal-free photoredox catalysts for organic synthesis. By changing the number and position of carbazolyl and cyano groups on the center benzene ring, CDCBs with a wide range of photoredox potentials are obtained to effectively drive the energetically demanding C­(sp³)–C­(sp²) cross-coupling of carboxylic acids and alkyltrifluoroborates with aryl halides via a photoredox/Ni dual catalysis mechanism. This work validates the utility of D–A fluorophores in guiding the rational design of metal-free photoredox catalysts for visible-light-promoted organic synthesis

Pseudocapacitive Properties of Two-Dimensional Surface Vanadia Phases Formed Spontaneously on Titania

Pseudocapacitive properties of V₂O₅-based adsorbates supported on TiO₂ nanoparticles, which form spontaneously as two-dimensional (2-D) nonautonomous surface phases (complexions) at thermodynamic equilibria, have been systematically measured. Surprisingly, surface amorphous films (SAFs), which form naturally at thermodynamic equilibria at 550–600 °C with self-regulating or “equilibrium” thicknesses on the order of 1 nm, exhibit superior electrochemical performance at moderate and high scan rates (20–500 mV/s) that are of prime importance for supercapacitor applications, as compared with submonolayer and monolayer adsorbates formed at lower equilibration temperatures. This study suggests a new direction to design and fabricate a novel class of supercapacitors and other functional devices via utilizing 2-D interfacial phases that can form spontaneously via facile, cost-effective, and highly scalable synthesis routes

Carbazolic Porous Organic Framework as an Efficient, Metal-Free Visible-Light Photocatalyst for Organic Synthesis

We report the visible-light-promoted photocatalytic activity of a highly porous carbazolic organic framework, Cz-POF-1, toward three prototypic organic transformations: net reductive dehalogenation of phenacyl bromide and its derivatives, net oxidative hydroxylation of arylboronic acids, and redox-neutral α-alkylation of aldehydes. We show that the extended π-conjugation in Cz-POF-1 enhances its visible light absorption, and the large porosity accelerates the reaction rate. For α-alkylation of aldehydes, Cz-POF-1 requires less strict reaction conditions and can be easily recovered and reused for up to 10 times. This work reveals a bright future for Cz-POFs as a new generation of metal-free photocatalysts for organic synthesis

Comparison Studies of Interfacial Electronic and Energetic Properties of LaAlO₃/TiO₂ and TiO₂/LaAlO₃ Heterostructures from First-Principles Calculations

By using first-principles electronic structure calculations, we studied electronic and energetic properties of perovskite oxide heterostructures with different epitaxial growth order between anatase TiO₂ and LaAlO₃. Two types of heterostructures, i.e., TiO₂ film grown on LaAlO₃ substrate (TiO₂/LaAlO₃) and LaAlO₃ film grown on TiO₂ substrate (LaAlO₃/TiO₂), were modeled. The TiO₂/LaAlO₃ model is intrinsically metallic and thus does not exhibit an insulator-to-metal transition as TiO₂ film thickness increases; in contrast, the LaAlO₃/TiO₂ model shows an insulator-to-metal transition as the LaAlO₃ film thickness increases up to 4 unit cells. The former model has a larger interfacial charge carrier density (<i>n</i> ∼ 10¹⁴ cm^–2) and smaller electron effective mass (0.47<i>m</i>_e) than the later one (<i>n</i> ∼ 10¹³ cm^–2, and 0.70<i>m</i>_e). The interfacial energetics calculations indicate that the TiO₂/LaAlO₃ model is energetically more favorable than the LaAlO₃/TiO₂ model, and the former has a stronger interface cohesion than the later model. This research provides fundamental insights into the different interfacial electronic and energetic properties of TiO₂/LaAlO₃ and LaAlO₃/TiO₂ heterostructures

Fine Tuning the Redox Potentials of Carbazolic Porous Organic Frameworks for Visible-Light Photoredox Catalytic Degradation of Lignin <i>β-</i>O‑4 Models

We report a facile approach to fine tune the redox potentials of π-conjugated porous organic frameworks (POFs) by copolymerizing carbazolic electron donor (D) and electron acceptor (A) based comonomers at different ratios. The resulting carbazolic copolymers (CzCPs) exhibit a wide range of redox potentials that are comparable to common transition-metal complexes and are used in the stepwise photocatalytic degradation of lignin β-O-4 models. With the strongest oxidative capability, CzCP100 (D:A = 0:100) exhibits the highest efficiency for the oxidation of benzylic β-O-4 alcohols, while the highly reductive CzCP33 (D:A = 66:33) gives the highest yield for the reductive cleavage of β-O-4 ketones. CzCPs also exhibit excellent stability and recyclability and represent a class of promising heterogeneous photocatalysts for the production of fine chemicals from sustainable lignocellulosic biomass

Tertiary Mg/MgCl₂/AlCl₃ Inorganic Mg²⁺ Electrolytes with Unprecedented Electrochemical Performance for Reversible Mg Deposition

Because of the high reactivity and sensitivity of Mg²⁺ electrolytes in organic solvents, developing facile methods of preparing high-performance Mg²⁺ electrolytes is still challenging and thus impedes the development of Mg batteries. In this study, a convenient method involving tertiary reactants, Mg powder, MgCl₂, and AlCl₃, was reported to prepare all-inorganic Mg²⁺ electrolytes (termed <b>MMAC</b> electrolytes) in ethereal solvents. These <b>MMAC</b> electrolytes exhibited unprecedented performance for reversible Mg deposition, Coulombic efficiencies at 90–100%, overpotential of 125–215 mV, and anodic stability up to 3.5–3.8 V (vs Mg). A comprehensive fundamental study of the <b>MMAC</b> electrolytes showed that the electron transfer and mass transport kinetics during Mg deposition and stripping were affected by solvent, working electrode, and the composition of the electrolytes. In brief, these tertiary <b>MMAC</b> electrolytes represent the most facile and reliable inorganic Mg electrolytes known to date

Metal-Free Electrocatalytic Aerobic Hydroxylation of Arylboronic Acids

Hydroxylation of arylboronic acids to aryl alcohols was realized by a scalable electrocatalytic method. The present electrochemical hydroxylation employs low-cost methyl viologen as an organic cathodic electrocatalyst and involves O₂ as a green and sustainable reactant. The electrochemical kinetic studies shown here can be a powerful tool to gain rich mechanistic and kinetic information and thus an in-depth understanding of the electrocatalytic mechanism

An Order–Disorder Transition in Surface Complexions and Its Influence on Crystal Growth of Boron-Rich Nanostructures

Controlled fabrication of boron-rich nanostructures was achieved by manipulating the processing temperature: high-temperature processing (1400–1500 °C) produced mainly tabular platelets with parallel twinning cross sections, whereas low-temperature processing (1100–1200 °C) facilitated the growth of star-shaped nanowires with cyclic twinning cross sections. This study revealed that this growth habit transition was related to the structural order of the adsorbed Ba atoms in nanoscale surficial films, which is a type of surface complexion (stable equilibrium phase-like surface states). It is demonstrated that an order–disorder transition in these surface complexions can play a critical role in determining the growth habits of crystals

Tetranuclear Gadolinium(III) Porphyrin Complex as a Theranostic Agent for Multimodal Imaging and Photodynamic Therapy

We describe herein the elaborate design of a Gd­(III)–porphyrin complex as a theranostic agent for multimodal imaging and photodynamic therapy. Far-red-emitting (665 nm) and high relaxivity (14.1 mM^–1 s^–1) with 107% increase upon binding to HSA (human serum albumin) (29.2 mM^–1 s^–1) together with efficiently generating singlet oxygen upon exposure to far-red light irradiation at 650 ± 20 nm demonstrate that this Gd­(III)–porphyrin complex with four Gd­(III)–DTTA units bound to tetraphenylporphyrin acts as a potentially theranostic agent with excellent performance for magnetic resonance imaging, optical imaging, and photodynamic therapy

Ultrafast barrierless photoisomerization and strong ultraviolet absorption of photoproducts in plant sunscreens

Sunscreens are aimed at protecting skin from solar ultraviolet (UV) irradiation. By utilizing femtosecond transient absorption spectroscopy and time-dependent density functional theory, we explain nature's selection of sinapoyl malate rather than sinapic acid as the plant sunscreen molecule. In physiological pH conditions, the two molecules are deprotonated, and their excited pi pi* states are found to relax to the ground states in a few tens of picoseconds via a barrierless trans-cis photoisomerization. After the cis-photoproduct is formed, the efficacy of sinapic acid is greatly reduced. In contrast, the efficacy of sinapoyl malate is affected only slightly because the cis-product still absorbs UV light strongly. In addition, protonated sinapic acid is found to be a good potential sunscreen molecule