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We present an analysis of reported magnetic field effects (MFEs) on the yield of formic acid produced by electrocatalytic reduction of carbon dioxide at a nanoparticle tin electrode [H. P. Pan et al., J. Phys. Chem. Lett. 11, 48-53 (2020)]. Radical pair spin dynamics simulations are used to show that (1) the Δg mechanism favored by Pan et al. is not sufficient to explain the observed magneto-current, (2) field-dependent spin relaxation, resulting from the anisotropy of the g-tensor of CO2•-, combined with the coherent singlet-triplet interconversion arising from isotropic hyperfine and Zeeman interactions, can quantitatively account for the observed MFE, and (3) modification of hyperfine interactions by isotopic substitution (1H → 2H and/or 12C → 13C) could be used to test both the proposed reaction mechanism and the interpretation presented here.Theoretical methods able to screen large sets (e.g., conformers) of possibly large compounds are needed in many typical quantum chemistry applications. For this purpose, we here extend the well-established simplified time-dependent density functional theory (sTD-DFT) method for the calculation of optical rotation. This new scheme is benchmarked against 42 compounds of the OR45 set as well as thirteen helicene derivatives and one bio-molecular system. The sTD-DFT method yields optical rotations in good quantitative agreement with experiment for compounds with a valence-dominated response, e.g., conjugated π-systems, at a small fraction of the computational cost compared to TD-DFT (1-3 orders of magnitude speed-up). For smaller molecules with a Rydberg state dominated response, the agreement between TD-DFT and the simplified version using standard hybrid functionals is somewhat worse but still reasonable for typical applications. Our new implementation in the stda code enables computations for systems with up to 1000 atoms, e.g., for studying flexible bio-molecules.The meta-generalized-gradient approximation (meta-GGA) of the exchange-correlation energy functional can provide appealing performance for the wide range of quantum chemistry and solid-state properties. So far, several meta-GGAs are proposed by fitting to the test sets or/and satisfying as many as known exact constraints. Although the density overlap is treated by meta-GGA functionals efficiently, for non-covalent interactions, a long-range dispersion correction is essential. In this work, we assess the benchmark performance of different variants of the Tao-Mo meta-GGA semilocal functional, i.e., TM [J. Tao and Y. Mo, Phys. Rev. Lett. 117, 073001 (2016)] and revTM [S. Jana, K. Sharma, and P. Samal, J. Phys. Chem. A 123, 6356 (2019)], with Grimme's D3 correction for several non-covalent interactions, including hydrogen-bonded systems. selleckchem We consider the zero, Becke-Johnson (BJ), and optimized power (OP) damping functions within the D3 method with both TM and revTM functionals. It is observed that the overall performance of the functionals gradually improved from zero to BJ and to OP damping. However, the constructed "OP" corrected (rev)TM + D3(OP) functionals perform considerably better compared to other well-known dispersion corrected functionals. Based on the accuracy of the proposed functionals, the future applicability of these methods is also discussed.The H+(CO)2 and D+(CO)2 molecular ions were investigated by infrared spectroscopy in the gas phase and in para-hydrogen matrices. In the gas phase, ions were generated in a supersonic molecular beam by a pulsed electrical discharge. After extraction into a time-of-flight mass spectrometer, the ions were mass selected and probed by infrared laser photodissociation spectroscopy in the 700 cm-1-3500 cm-1 region. Spectra were measured using either argon or neon tagging, as well as tagging with an excess CO molecule. In solid para-hydrogen, ions were generated by electron bombardment of a mixture of CO and hydrogen, and absorption spectra were recorded in the 400 cm-1-4000 cm-1 region with a Fourier-transform infrared spectrometer. A comparison of the measured spectra with the predictions of anharmonic theory at the CCSD(T)/ANO1 level suggests that the predominant isomers formed by either argon tagging or para-hydrogen isolation are higher lying (+7.8 kcal mol-1), less symmetric isomers, and not the global minimum proton-bound dimer. Changing the formation environment or tagging strategy produces other non-centrosymmetric structures, but there is no spectroscopic evidence for the centrosymmetric proton-bound dimer. The formation of higher energy isomers may be caused by a kinetic effect, such as the binding of X (=Ar, Ne, or H2) to H+(CO) prior to the formation of X H+(CO)2. Regardless, there is a strong tendency to produce non-centrosymmetric structures in which HCO+ remains an intact core ion.The synthesis of lanthanide doped up-converting nanoparticles (UCNPs), whose morphological, structural, and luminescence properties are well suited for applications in optoelectronics, forensics, security, or biomedicine, is of tremendous significance. The most commonly used synthesis method comprises decomposition of organometallic compounds in an oxygen-free environment and subsequent infliction of a biocompatible layer on the particle surface. In this work, hydroxyl-carboxyl (-OH/-COOH) type of chelating agents (citric acid and sodium citrate) are used in situ for the solvothermal synthesis of hydrophilic NaY0.5Gd0.3F4Yb,Er UCNPs from rare earth nitrate salts and different fluoride sources (NaF, NH4F, and NH4HF2). X-ray powder diffraction showed crystallization of cubic and hexagonal NaY0.5Gd0.3F4Yb,Er phases in nano- and micro-sized particles, respectively. The content of the hexagonal phase prevails in the samples obtained when Na-citrate is used, while the size and shape of the synthesized mesocrystals are affected by the choice of fluoride source used for precipitation. All particles are functionalized with citrate ligands and emit intense green light at 519 nm and 539 nm (2H11/2, 4S3/2 → 4I15/2) under near infrared light. The intensity of this emission is distressed by the change in the origin of phonon energy of the host matrix revealed by the change in the number of the excitation photons absorbed per emitted photon.
Homepage: https://www.selleckchem.com/products/Cytarabine(Cytosar-U).html
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