Magnussen Crews (roadvacuum1)

Flavin compounds are of great interest in biochemistry because of their diverse functions in catalytic and photochemical processes. The intrinsic optical properties of flavins depend sensitively on their environment such as complexation with metal ions. Herein, we characterize the interaction of alkali metal ions (M+) with riboflavin (RF, vitamin B2). To this end, two different experimental spectroscopic approaches are employed to determine the structural, vibrational, energetic, and optical properties of M+RF complexes by comparison with density functional theory (DFT) calculations at the PBE0/cc-pVDZ level. First, infrared multiple photon dissociation (IRMPD) spectra recorded at room temperature demonstrate that M+ binds to one of the two available nucleophilic carbonyl groups (CO2, CO4) of RF, denoted O2 and O4+ isomers, as revealed by characteristic shifts of the CO stretch modes upon metalation. Second, the optical spectrum of K+RF is recorded between 428 and 529 nm in a cryogenic ion trap held at 6 K by+RF the O2 isomer is strongly favored due to the additional interaction with the side chain. Although the S1 energies of M+RF(O2) and M+LF(O2) are quite similar, because the ππ* transition is localized on the same isoalloxazine chromophore for both flavins, the vibrational structures are strongly different because the soft bending potential for the M+···flavin interaction is strongly affected by the ribityl side chain at N10. In contrast to H+RF, which prefers protonation at N1, steric repulsion of the larger M+ ions with the ribityl side chain prevents metalation at N1, leading to the formation of the O2 global minimum.Magnetic anisotropy is essential for permanent magnets to maintain their magnetization along specific directions. Understanding and controlling the magnetic anisotropy on a single-molecule scale are challenging but of fundamental importance for the future's spintronic technology. Here, by using scanning tunneling microscopy (STM), we demonstrated the ability to control the magnetic anisotropy by tuning the ligand field at the single-molecule level. We constructed a molecular magnetic complex with a single Mn atom and an organic molecule (4,4'-biphenyldicarbonitrile) as a ligand via atomic manipulation. Inelastic tunneling spectra (IETS) show that the Mn complex has much larger axial magnetic anisotropy than individual Mn atoms, and the anisotropy energy can be tuned by the coupling strength of the ligand. With density functional theory calculations, we revealed that the enhanced magnetic anisotropy of Mn arising from the carbonitrile ligand provides a prototype for the engineering of the magnetism of quantum devices.Upon application of a multicomponent Petasis reaction, a broad range of NH-sulfoximines and boronic acids react with glyoxalic acid to afford the corresponding 2-substituted acetic acids with N-bound sulfoximidoyl groups. The protocol features excellent yields under ambient, metal-free conditions and short reaction times. Furthermore, the applicability of 2-sulfoximidoyl acetic acids as building blocks for synthesizing sulfoximine-based benzodiazepine analogues was demonstrated.Defects are ubiquitous in semiconductors and critical to photo(electro)chemical performance, but the change of defect properties under light irradiation remains poorly understood. Herein, we studied defect change properties of Ta3N5 with transient absorption (TA) spectroscopy. A broad transient absorption (>650 nm) was observed and attributed to trapped electrons in oxygen impurities (substitution oxygen at nitrogen sites, ON), and two bleach signals at 510 and 580 nm were obtained and ascribed to free holes of Ta3N5. The charge recombination between the trapped electrons and the free holes is sensitively related to ON defects. The trap-detrapping recombination is retarded by increase of excitation intensity, which is contrary to the normal dependence of charge dynamics on excitation intensity. This abnormal dependen