Two-dimensional sp2 carbon–conjugated covalent organic frameworks

We synthesized a two-dimensional (2D) crystalline covalent organic framework (sp2c-COF) that was designed to be fully π-conjugated and constructed from all sp2-carbons by C=C condensation reactions of tetrakis(4-formylphenyl)pyrene and 1,4-phenylenediacetonitrile. The C=C linkages topologically connect pyrene knots at regular intervals into a 2D lattice with π-conjugations extended along both x and y directions, and develop an eclipsed layer framework rather than the more conventionally obtained disordered structures. The sp2c-COF is a semiconductor with a discrete band gap of 1.9 eV and can be chemically oxidized to enhance conductivity by 12 orders of magnitude. The generated radicals are confined on the pyrene knots, enabling the formation of a paramagnetic carbon structure with high spin density. The sp2-carbon framework induces ferromagnetic phase transition to develop spin-spin coherence and align spins unidirectionally across the material

Elucidation of the Mechanism of Greenhouse Gas Generation by Abiotic Transformation of Nutrient Ions Flowing into Closed Water Areas with Little Phytoplankton

In Mikawa Bay and Ise Bay, many tidal flats, shallow areas, and seaweed beds have been lost due to land reclamation, and the pollution inflow from domestic and industrial wastewater has increased, causing environmental deterioration such as red and blue tides. To prevent their occurrence, the hyporheic zone of the brackish lake leading to these bays was dredged and covered with sand, and sewerage systems were constructed around the surrounding areas. Furthermore, the water in this lake is regularly substituted with new river water but unregulated agricultural wastewater flows into the lake. Nutrient ions from nitrogen fertilizers in this wastewater are passively decomposed and released into the atmosphere as a greenhouse gas N2O. We report that ClO2– ions, classified as disinfection byproducts detected in this water body, promote the production of •N and •NO radicals through the abiotic transformation of NH4NO3 from nitrogen fertilizers in aqueous solutions. Because these radicals are highly reactive and have a small energy gap between singly occupied molecular orbital (SOMOs), they generate N2O through a heterogeneous coupling reaction and release N2O from water to the atmosphere. Abiotic transformation mechanisms of nutrient ions provide information for resolving biodiversity crises and N2O emissions problems associated with marine environmental restoration

Conformational ensemble of a multidomain protein explored by Gd3+ electron paramagnetic resonance

Despite their importance in function, the conformational state of proteins and its changes are often poorly understood, mainly because of the lack of an efficient tool. MurD, a 47-kDa protein enzyme responsible for peptidoglycan biosynthesis, is one of those proteins whose conformational states and changes during their catalytic cycle are not well understood. Although it has been considered that MurD takes a single conformational state in solution as shown by a crystal structure, the solution nuclear magnetic resonance (NMR) study suggested the existence of multiple conformational state of apo MurD in solution. However, the conformational distribution has not been evaluated. In this work, we investigate the conformational states of MurD by the use of electron paramagnetic resonance (EPR), especially intergadolinium distance measurement using double electron-electron resonance (DEER) measurement. The gadolinium ions are fixed on specific positions on MurD via a rigid double-arm paramagnetic lanthanide tag that has been originally developed for paramagnetic NMR. The combined use of NMR and EPR enables accurate interpretation of the DEER distance information to the structural information of MurD. The DEER distance measurement for apo MurD shows a broad distance distribution, whereas the presence of the inhibitor narrows the distance distribution. The results suggest that MurD exists in a wide variety of conformational states in the absence of ligands, whereas binding of the inhibitor eliminates variation in conformational states. The multiple conformational states of MurD were previously implied by NMR experiments, but our DEER data provided structural characterization of the conformational variety of MurD

Near-IR Light-Induced Electron Transfer via Dynamic Quenching

The utilization of near-infrared light is an important objective for the high-efficiency utilization of solar energy. Here, we describe a new class of a near-infrared light-induced electron transfer system using a distorted phthalocyanine as a photosensitizer. We revealed that the appropriate modification of distorted phthalocyanine affords a near-infrared absorbing dye with high photostability and long excitation lifetime, and a near-infrared light-induced electron transfer system was successfully established using the dye. The mechanistic investigation clarified that the electron transfer system works via a dynamic quenching mechanism. The system generated a long-lived anion radical species of the dye upon near-infrared light irradiation (>750 nm)

Near-IR Light-Induced Electron Transfer via Dynamic Quenching

The utilization of near-infrared light is an important objective for the high-efficiency utilization of solar energy. Here, we describe a new class of a near-infrared light-induced electron transfer system using a distorted phthalocyanine as a photosensitizer. We revealed that the appropriate modification of distorted phthalocyanine affords a near-infrared absorbing dye with high photostability and long excitation lifetime, and a near-infrared light-induced electron transfer system was successfully established using the dye. The mechanistic investigation clarified that the electron transfer system works via a dynamic quenching mechanism. The system generated a long-lived anion radical species of the dye upon near-infrared light irradiation (>750 nm)

Near-IR Light-Induced Electron Transfer via Dynamic Quenching

The utilization of near-infrared light is an important objective for the high-efficiency utilization of solar energy. Here, we describe a new class of a near-infrared light-induced electron transfer system using a distorted phthalocyanine as a photosensitizer. We revealed that the appropriate modification of distorted phthalocyanine affords a near-infrared absorbing dye with high photostability and long excitation lifetime, and a near-infrared light-induced electron transfer system was successfully established using the dye. The mechanistic investigation clarified that the electron transfer system works via a dynamic quenching mechanism. The system generated a long-lived anion radical species of the dye upon near-infrared light irradiation (>750 nm)