We report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI molecule at room temperature using the cluster microsolvation approach including 32 water molecules. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms the Stuttgart-Köln relativistic effective-core potentials were utilized with their associated valence basis sets. Starting from the optimized geometry of SmI embeded in the microsolvation environment, we find a swift substitution of the iodine ions by eight tightly bound water molecules around Sm(II). Through the Sm-O radial distribution function and the evolution of the Sm-O distances, the present study predicts a first rigid Sm(II) solvation shell from 2.6 to 3.4 Å, whose integration leads to a coordination number of 8.4 water molecules, and a second softer solvation sphere from 3.5 to ca. 6 Å. The Sm(II)-O radial distribution function is in excellent agreement with that reported for Sr from EXAFS studies, a fact that can be explained because Sr and Sm have almost identical ionic radii (ca. 1.26 Å) and coordination numbers: 8 for Sr and 8.4 for Sm. The theoretical EXAFS spectrum was obtained from the BOMD trajectory and is discussed in the light of the experimental spectra for Sm(III). Once microsolvation is achieved, no water exchange events were found to occur around Sm, in agreement with the experimental data for Eu (which has a nearly identical charge-to-ionic radius relation as Sm), where the mean residence time of a water molecule in [Eu(HO)] is known to be ca. 230 ps.

The high-valent molybdenum(VI) N-heterocyclic carbene complexes, (NHC)MoO 2 (1) and (NHC)MoO(N t Bu) (2) (NHC = 1,3bis(3,5-di-tert-butyl-2-phenolato)-benzimidazol-2-ylidene), are investigated toward their catalytic potential in the deoxygenation of nitroarenes. Using pinacol as the sacrificial and green reductant, both complexes are shown to be very active (pre)catalysts for this transformation allowing a reduction of the catalyst loading down to 0.25 mol %. Mechanistic investigations show μ-oxo bridged molybdenum(V) complexes [(NHC)MoO] 2 O (4) and [(NHC)Mo-(N t Bu)] 2 O (5) as well as zwitterionic pinacolate benzimidazolium complex 6, with a doubly protonated NHC ligand, to be potentially active species in the catalytic cycle. Both 4 and 5 can be prepared independently by the deoxygenation of 1 and 2 using triethyl phosphine (PEt 3 ) or triphenyl phosphine (PPh 3 ) and were shown to exhibit an unusual multireferenced ground state with a very small singlet−triplet gap at room temperature. Computational studies show that the spin state plays an unneglectable role in the catalytic process, efficiently lowering the reaction barrier of the deoxygenation step. Mechanistic details, putting special emphasis on the fate of the catalyst will be presented and potential routes how nitroarene reduction is facilitated are evaluated.

The hydration features of [Mg(HO)] and [Ca(HO)] clusters with n = 3-6, 8, 18, and 27 were studied by means of Born-Oppenheimer molecular dynamics simulations at the B3LYP/6-31+G** level of theory. For both ions, it is energetically more favorable to have all water molecules in the first hydration shell when n ≤ 6, but stable lower coordination average structures with one water molecule not directly interacting with the ion were found for Mg at room temperature, showing signatures of proton transfer events for the smaller cation but not for the larger one. A more rigid octahedral-type structure for Mg than for Ca was observed in all simulations, with no exchange of water molecules to the second hydration shell. Significant thermal effects on the average structure of clusters were found: while static optimizations lead to compact, spherically symmetric hydration geometries, the effects introduced by finite-temperature dynamics yield more prolate configurations. The calculated vibrational spectra are in agreement with infrared spectroscopy results. Previous studies proposed an increase in the coordination number (CN) from six to eight water molecules for [Ca(HO)] clusters when n ≥ 12; however, in agreement with recent measurements of binding energies, no transition to a larger CN was found when n > 8. Moreover, the excellent agreement found between the calculated extended X-ray absorption fine structure spectroscopy spectra for the larger cluster and the experimental data of the aqueous solution supports a CN of six for Ca.

In this work, a theoretical investigation was made to assess the coordination properties of Pb(ii) in [Pb(HO)] clusters, with n = 4, 6, 8, 12, and 29, as well as to study proton transfer events, by means of Born-Oppenheimer molecular dynamics simulations at the B3LYP/aug-cc-pVDZ-pp/6-311G level of theory, that were calibrated in comparison with B3LYP/aug-cc-pVDZ-PP/aug-cc-pVDZ calculations. Hemidirected configurations were found in all cases; the radial distribution functions (RDFs) produced well defined first hydration shells (FHSs) for n = 4,6,8, and 12, that resulted in a coordination number CN = 4, whereas a clear-cut FHS was not found for n = 29 because the RDF did not have a vacant region after the first maximum; however, three water molecules remained directly interacting with the Pb ion for the whole simulation, while six others stayed at average distances shorter than 4 Å but dynamically getting closer and farther, thus producing a CN ranging from 6 to 9, depending on the criterion used to define the first hydration shell. In agreement with experimental data and previous calculations, proton transfer events were observed for n≤8 but not for n≥12. For an event to occur, a water molecule in the second hydration shell had to make a single hydrogen bond with a water molecule in the first hydration shell.

We report the results of Born-Oppenheimer molecular dynamics (BOMD) simulations on the aqueous solvation of the SmI molecule and of the bare Sm cation at room temperature using the cluster microsolvation approach including 37 and 29 water molecules, respectively. The electronic structure calculations were done using the M062X hybrid exchange-correlation functional in conjunction with the 6-31G** basis sets for oxygen and hydrogen. For the iodine and samarium atoms, the Stuttgart-Köln relativistic effective-core potentials were utilized with their associated valence basis sets. When SmI is embedded in the microsolvation environment, we find that substitution of the iodine ions by water molecules around Sm(III) cannot be achieved due to an insufficient number of explicit water molecules to fully solvate the four separate metal and halogen ions. Therefore, we studied the solvation dynamics of the bare Sm cation with a 29-water molecule model cluster. Through the Sm-O radial distribution function and the evolution of the Sm-O distances, the present study yields a very tightly bound first rigid Sm(III) solvation shell from 2.3 to 2.9 Å whose integration leads to a coordination number of 9 water molecules and a second softer solvation sphere from 3.9 to 5 Å with 12 water molecules. No water exchange processes were found. The theoretical EXAFS spectrum is in excellent agreement with the experimental spectrum for Sm(III) in liquid water. The strong differences between the solvation patterns of Sm(III) vs Sm(II) are discussed in detail.

Ce(iv) complexes with multiple bonds display similar f0 fractions, but different f/d hybridization, 5d-orbital energies, and TIP levels.

The 4f-block metal compounds with 2,2'-bipyridine of empirical composition M( 2 -bipy) 4 , M = La, Ce, and Nd were prepared fifty years ago by Herzog. [1][2] These compounds were prepared as part of a systematic investigation of the reaction of the metal salts with Li 2 (bipy) and bipy in thf. 3 The compounds with M = Eu, Yb were prepared shortly thereafter from the metals dissolved in liquid ammonia and bipyridine. 4 The synthesis of the remainder of the 4fblock metals, except Pm, was published in 2000, adapting the synthetic methodology used by Herzog, i.e. using metal iodides or bis-trimethylsilyl amides as starting materials. 5 The compounds are deeply colored, often described as black, air and moisture sensitive solids that are not volatile. They are insoluble in hydrocarbon and ethereal solvents. The solid-state effective magnetic moments ( eff ) at room temperature for M = La, Ce, and Nd were 1.82  B , 2.85  B and 3.62  B , respectively [1][2] show that the compounds are not based on the metals in their zero oxidation states. The room temperature solution (MeCN) magnetic moments for Eu and Yb of 5.8  B and 2.8  B , respectively, were ascribed to antiferromagnetic coupling between the metal-based spins and the ligand-based spins, the latter being formulated as bipy radical anions. 4 The UV-Vis spectra of M = Tb and Yb clearly show signatures of bipy radical anions but their complexity rendered a detailed interpretation impossible. 6 The solidstate effective moments ( eff ) at room temperature were reported for the entire 4f-block metals (except Pm) along with crystals structures of Sm, Eu, Yb, and Lu. 5,7 The  eff values agree with those reported by Herzog but disagree with those by Feistel 4 (see discussion) and were interpreted according to the Lewis structure [M(III)(bipy) 2-(bipy) •-(bipy) 2 ], except for Eu, which was based on Eu(II). The bipyridine ligands are clearly non-innocent or perhaps more descriptively referred to as redox active 8 but a deeper level of understanding of the electronic structure was not developed.

We implement molecular dynamics (MD) simulations to explore the relaxation mechanisms involved in the description of translational diffusion and rotational dynamics in water/hydrocarbon interfaces. The analysis of density profiles, selfdiffusion coefficients, and nuclear magnetic resonance (NMR) relaxation properties as a function of the confinement layer width and type of hydrocarbons improves the understanding of confined water properties at water/oil interfaces. Density profile fluctuations reveal the presence of water−oil interactions close to the interface. MD results show that self-diffusion coefficients and NMR relaxation times of planar and cylindrical water/oil interfaces are strongly influenced by layer thickness and geometry. Shorter (between 20 and 60%) self-diffusion coefficients and 1 H NMR relaxation times were obtained for water/n-pentane, water/n-decane, and water/n-hexadecane systems than bulk diffusion coefficients. An increase in Larmor frequency from 2.3 MHz to 400 MHz shows that longitudinal relaxation time (T 1 ) of confined oil has slightly larger differences at higher frequencies than the transverse relaxation time (T 2 ). At 400 MHz, n-alkanes (n-pentane, ndecane, and n-hexadecane) exhibit longer relaxation times than at smaller frequency values (2.3 and 22 MHz). Analysis of spin−spin and spin−lattice times provides relevant information about inter-and intramolecular relaxation mechanisms of water and oil as a function of geometry and width of the interface layer. These MD results suggest that the strength of confinement and geometry play a vital role in the diffusion and NMR relaxation properties of water/oil interfaces.