ChemPhotoChem最新文献

Cost-effective and efficient photocatalysis is highly desirable in chemical synthesis. Here a honeycomb-like porous carbon nitride (P-C₃N₄) with defects was prepared by a simple one-step calcination of an aqueous urea solution. By introducing the hierarchical porous structure and defects, the P-C₃N₄ was able to make more efficient use of visible light and enhance mass transfer. This catalyst exhibits 44% longer carrier lifetime than bulk C₃N₄ and can be easily scaled up and demonstrates excellent catalytic reactivity in various types of cross-dehydrogenative coupling (CDC) reactions under visible light irradiation. A very high reaction rates of 6467 and 10,625 μmolg⁻¹h⁻¹ were achieved by P-C₃N₄ in model reaction of aza-Henry type and Mannich type of CDC reaction, which are 26.8 and 2.8 times higher than previous reports, respectively. Moreover, P-C₃N₄ can maintain 95% yield of target product in aza-Henry CDC reaction after 21 cycles of repeated experiments. Our low-cost, easy-to-process, and highly efficient C₃N₄ photocatalyst is expected to bring new insights in chemical synthesis.

A novel ratiometric fluorescent platform, composed of a rodamine derivative and dansyl moiety, is designed and synthesized as a prototype sensor capable of responding to proton concentration. It is well known that, under neutral or basic conditions, rhodamine derivatives in their spirolactam form do not absorb or emit in the visible range. However, metal or proton ions can induce spirolactam ring opening, resulting in visible absorption and strong fluorescence emission. Although many rhodamine derivatives have been developed to detect metal ions or pH changes, the sensing mechanism related to spirolactam ring opening remains not fully understood. To address this, the hybrid platform described in this work is investigated across a wide pH range, particularly under high proton concentration, to study and clarify the proton-mediated ring opening mechanism of the rhodamine spirolactam. This investigation combined spectrophotometric and potentiometric measurements, supported by DFT calculations.

Chiral liquid crystals (LCs) are essential for optoelectronic devices. Two representative achiral luminescent compounds, pyrene and perylene, are doped into a mixed chiral nematic LC (N*-LC) comprising achiral LC 4′-pentyl-4-biphenylcarbonitrile (5CB) and chiral LC 2-octyl-4-[4-(hexyloxy)benzoyloxy]benzoate (2OHBB). Consequently, despite being achiral luminescent materials, the doped pyrene and perylene successfully generate strong circularly polarized luminescence (CPL) from the resulting chiral N*-LC composed of 5CB and 2OHBB. The rotation direction of the extracted CPL can be controlled by the chirality of the LC molecule 2OHBB. Furthermore, these N*-LCs demonstrate continuous and reversible CPL responses depending on the presence or absence of a direct current (DC) electric field. This result demonstrates the successful design of a CPL LC system, where the rotation direction of CPL can be controlled not only by the chirality of 2OHBB, but also through the ON–OFF–ON switching of the DC electric field. This behavior is attributed to a reversible transition from a helical structure to another ordered structure (chiral nematic phase to chiral nematic phase transition). This study provides an effective strategy for controlling CPL properties by exposing N*-LC to DC electric fields and for developing functional CPL devices.

A Ruddlesden–Popper phase-layered perovskite Fe₂SnO₄ is coupled with graphitic carbon nitride (gCN) in an S-scheme heterojunction. The Fe₂SnO₄/gCN heterojunction is synthesized using the sonication–calcination method. The layered structure of Fe₂SnO₄ enhances charge migration toward the junction interface and enables the internal electric field, increasing the charge separation in the overall composite. The optical characteristics of Fe₂SnO₄/gCN show an excellent visible light utilization ability, thus expanding its applicability in solar (visible light)-driven catalytic approaches. A significant formate generation rate (2.043 mM h⁻¹ gcat⁻¹) is measured over the photocatalyst using the aqueous bicarbonate as the CO₂ precursor. The isotope labeling test corroborates the generation of formate from bicarbonate. Fe₂SnO₄/gCN also displays a good stability over five reaction–regeneration cycles. The band structure of Fe₂SnO₄/gCN in conjunction with the radicals detected via spin trapping confirms the development of the S-scheme heterojunction in Fe₂SnO₄/gCN. Herein, the fabrication of the layered perovskite-based S-scheme heterojunction paves a path for pursuing the solar-driven environmental remediation strategies.

Herein, a series of supramolecular electro-optic (EO) dendrimers (EOD1-6) constructed using push–pull tetraene chromophores (PPT-phores) and Fréchet-type generation-1 benzyl ether dendrons with 2,3,5,6-tetrafluorophenyl or 2,4,6-trifluorophenyl groups at the periphery is presented. The fluorophenyl moieties possess enhanced CH acidity to form extended CH···F hydrogen bonds within complex functional dendrimers. Through comprehensive studies of optical absorption, electric field poling, EO activity, and thermal stability of EOD1-6/poly (methyl methacrylate) films, along with X-ray analyses of dendritic model compounds, it is elucidated that nonclassical hydrogen bonding of fluorophenyl synthons plays a pivotal role in modulating the strong dipole–dipole electrostatic interactions of PPT-phores. It facilitates the dipole orientation and enhances the stability of supramolecular EO dendrimers in poled films. Two of these dendrimers exhibit large r₃₃ values of ≈170 pm V⁻¹ at 1306 nm and ≈120 pm V⁻¹ at 1541 nm, among the best EO activities to date for organic materials as certified by prism-coupled attenuated total reflection spectroscopy. Furthermore, examining subgap absorption for the films provides insights into the Urbach energy tail states. The notable properties and synthetic efficacy demonstrated by these dendrimers represent a transformative step in developing highly efficient, thermally stable, and low loss supramolecular organic EO materials for photonic applications.

Easily accessible small organic fluorophores with multiplexing capabilities are of interest for a variety of fields. Here, a combination of experimental and computational methods reveals previously unknown, yet potentially useful properties of one of the original squaraine dyes, i.e., bis-kryptopyrrol-2-yl squaraine. The rotational flexibility of the pyrrole units around the squaraine core allows for this dye to act as a viscosity probe. In addition to the previously known fluorescence emission in solution with λ_em in the 550–580 nm range, this dye exhibits solid-state emission with λ_em at ≈800 nm. Thus, this dye is a dual-state emitter. density functional theory/time-dependent density functional theory calculations and concentration-dependent studies, in both solution and solid-state, indicate aggregated form of these dyes is responsible for the solid-state emission in the near-IR range.

While pursuing the exploration of porphyrin/fluorene combinations at the molecular level and their application as luminescent photosensitizers for two-photon photodynamic therapy (2P-PDT), we wondered about the impact of adding electron-releasing endgroups to these molecular structures. Furthermore, we also wondered about the influence of spacers within the arms of these star-shaped architectures and about the impact of the metalation of these free-base porphyrins by zinc. To address these questions, we synthesized a series of ten novel star-shaped meso-tetraarylporphyrins, featuring various aromatic rings with 1,2-ethenyl fluorenyl and/or 1,2-ethynyl spacers, capped by diphenylamine endgroups. The linear and nonlinear optical properties of these compounds were characterized through absorption, emission, and two-photon excited fluorescence studies, thereby screening the impact of endgroups, metalation and arm composition on the optical parameters of interest. Subsequently, their singlet oxygen-photosensitizing properties were also evaluated. The enhanced properties observed for compounds presenting diphenylamino (DPA) endgroups in comparison to analogs with none, along with the impact of metalation by Zn(II) and that of 1,2-ethenyl versus 1,2-ethynyl linkers on these, were eventually analyzed using classical figures of merit. This contribution highlights the strong potential of DPA-capped star-shaped free-base porphyrins as fluorescent photosensitizers for combined 2P-PDT and imaging applications.

Understanding the mechanism through which a photochemical reaction proceeds grants access to thermodynamic and kinetic parameters that allow its optimization for large-scale applications. In the last few years, photocatalytic systems have been major players in scientific developments on research fields of primary importance, including solar fuel generation in artificial photosynthesis, and the use of excited organic radical ions as photocatalysts in thermodynamically challenging reactions of utmost synthetic relevance. Generally, time-resolved spectroscopic approaches are the main experimental tools to investigative the dynamics of photoactive systems, with pump-probe-based ones being the golden standard in photophysical and photochemical research. However, for photocatalytic systems in which multiple photons are required, which is generally the case for photosynthetic reactions and those promoted by excited organic radical ions, the pump-probe approach is no longer sufficient since it is based on a single photon-to-electron ratio. This is where a second actinic pump excitation comes into play in what is known as pump-pump-probe spectroscopy. In this review, we explore how this approach is used to unravel the mechanism of photocatalytic systems triggered by light using different probes of UV–vis absorption and resonance Raman scattering in varying time scales.

A visible light photoswitchable diarylethene–perylenebisimide (DAE–PBI) dyad, incorporating bromine heavy atoms and a ketone linker in the molecular framework, is developed. In order to enhance the visible light-induced cyclization reactivity of a DAE–PBI dyad, in this study, an “internal heavy atom effect” with the “El-Sayed rule” into the molecular design is incorporated. From the theoretical calculation on the contribution ratio of bromine atoms to the molecular orbital (MO) in lowest unoccupied molecular orbitals (LUMOs) and the value of spin–orbit coupling, it is expected that the designed DAE–PBI dyad has high reactivity for visible light-induced cyclization reactions. The synthesized dyad exhibits efficient visible light-induced cyclization reaction not only in heavy atom-containing solvents but also in typical heavy atom-free solvents. These results indicate that the combination of the internal heavy atom effect and the El-Sayed rule effectively contributes to the visible light-induced cyclization reactivity in the dyad. These results will pave the way for new molecular designs to develop UV-free photoswitchable molecules.

Rare-metal-free luminophores that exhibit room-temperature phosphorescence (RTP) in the solid state and polymer film have attracted significant attention in various fields, including imaging, sensing, and optoelectronic technologies. Herein 1,4-dibenzolyl-2-siloxy-5-(silylmethoxy)benzenes are reported as novel RTP luminophores. Thermal analysis reveals that the unsymmetrical molecular structure of the benzene derivatives results in lower melting points compared to their symmetrical counterparts. Their solid-state RTP is highly dependent on the siloxy group. The choice of tert-BuPh₂SiO group is essential for achieving efficient RTP in the microcrystalline state; the quantum yields ranged from 0.40 to 0.58, unlike the choice of tert-BuMe₂SiO. Notably, poly(methyl methacrylate) films doped with the benzene derivatives emitted RTP under vacuum conditions with quantum yields ranging from 0.06 to 0.09, irrespective of the siloxy group. Theoretical calculations suggest that the RTP occurs via excitation involving intramolecular charge-transfer from the siloxy and silylmethoxy moieties to the benzoyl groups, followed by intersystem crossing from the lowest singlet excited state (S₁) to the second-lowest triplet excited state (T₂), and subsequent internal conversion to the lowest excited triplet state (T₁). Furthermore, the polymer film doped with one of the benzene derivatives is demonstrated to function as a molecular oxygen scavenger within a polymer matrix.