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Treating 195Pt nuclear magnetic resonance parameters in solution remains a considerable challenge from a quantum chemistry point of view, requiring a high level of theory that simultaneously takes into account the relativistic effects, the dynamic treatment of the solvent–solute system, and the dynamic electron correlation. A combination of Car-Parrinello molecular dynamics (CPMD) and relativistic calculations based on two-component zeroth order regular approximation spin–orbit Kohn–Sham (2c-ZKS) and four-component Dirac–Kohn–Sham (4c-DKS) Hamiltonians is performed to address the solvent effect (water) on the conformational changes and J PtPt 1 coupling. A series of bridged PtIII dinuclear complexes [L1–Pt2(NH3)4(Am)2–L2]n+ (Am = α–pyrrolidonate and pivalamidate; L = H2O, Cl−, and Br−) are studied. The computed Pt–Pt coupling is strongly dependent on the conformational dynamics of the complexes, which, in turn, is correlated with the trans influence among axial ligands and with the angle N–C–O from the bridging ligands. The J-coupling is decomposed in terms of dynamic contributions. The decomposition reveals that the vibrational and explicit solvation contributions reduce J PtPt 1 of diaquo complexes (L1 = L2 = H2O) in comparison to the static gas-phase magnitude, whereas the implicit solvation and bulk contributions correspond to an increase in J PtPt 1 in dihalo (L1 = L2 = X−) and aquahalo (L1 = H2O; L2 = X−) complexes. Relativistic treatment combined with CPMD shows that the 2c-ZKS Hamiltonian performs as well as 4c-DKS for the J PtPt 1 coupling. [ABSTRACT FROM AUTHOR]

Glyphosate is a widely used herbicide, and its protonation and deprotonation sites are fundamental to understanding its properties. In this work, the sodiated, protonated, and deprotonated glyphosate were evaluated in the gas phase by infrared multiple photon dissociation spectroscopy to determine the exact nature of these coordination, protonation, and deprotonation states in the gas phase. In this context, Natural Bond Orbital analyses were carried out to unravel interactions that govern glyphosate (de)protonation states in the gas phase. The solvent effect on the protonation/deprotonation equilibria was also investigated by implicit (Solvation Model Based on Density and polarizable continuum models) and explicit solvation models (Monte Carlo and Molecular Dynamics simulations). These results show that glyphosate is protonated in the phosphonate group in the gas phase because of the strong hydrogen bond between the carboxylic oxygen (O7) and the protonated phosphonate group (O8–H19), while the most stable species in water is protonated at the amino group because of the preferential interaction of the NH2+ group and the solvent water molecules. Similarly, deprotonated glyphosate [Glyp−H]− was shown to be deprotonated at the phosphonate group in the gas phase but not in solution, also because of the preferential solvation of the NH2+ group present in the other deprotomers. Therefore, these results show that the stabilization of the protonated amino group by the solvent molecules is the governing factor of the (de)protonation equilibrium of glyphosate in water. [ABSTRACT FROM AUTHOR]

The Diels–Alder reaction of three chiral dihydro‐2H‐[2,3‐a]oxazolopyridines with N‐methylmaleimide afforded the corresponding chiral cycloadducts as diastereomeric mixtures. In the presence of a solvent, some of the originally formed adducts underwent isomerisation to new isoquinuclidines. [ABSTRACT FROM AUTHOR]

We report the structural, vibrational, and optical properties of americium formate (Am(CHO2)3) crystals synthesized via the in situ hydrolysis of dimethylformamide (DMF). The coordination polymer features Am3+ ions linked by formate ligands into a three‐dimensional network that is isomorphous to several lanthanide analogs, (e. g., Eu3+, Nd3+, Tb3+). Structure determination revealed a nine‐coordinate Am3+ metal center that features a unique local C3v symmetry. The metal–ligand bonding interactions were investigated by vibrational spectroscopy, natural localized molecular orbital calculations, and the quantum theory of atoms in molecules. The results paint a predominantly ionic bond picture and suggest the metal‐oxygen bonds increase in strength from Nd−O

An ab initio molecular dynamics investigation of the solvent effect (water) on the structural parameters, 195Pt NMR spin–spin coupling constants (SSCCs) and chemical shifts of a series of pyridonate-bridged PtIII dinuclear complexes is performed using Kohn–Sham (KS) Car–Parrinello molecular dynamics (CPMD) and relativistic hybrid KS NMR calculations. The indirect solvent effect (via structural changes) has a dramatic effect on the 1JPtPt SSCCs. The complexes exhibit a strong trans influence in solution, where the Pt–Pt bond lengthens with increasing axial ligand σ-donor strength. In the diaqua complex, where the solvent effect is more pronounced, the SSCCs averaged for CPMD configurations with explicit plus implicit solvation agree much better with the experimental data, while the calculations for static geometry and CPMD unsolvated configurations show large deviations with respect to experiment. The combination of CPMD with hybrid KS NMR calculations provides a much more realistic computational model that reproduces the large magnitudes of 1JPtPt and 195Pt chemical shifts. An analysis of 1JPtPt in terms of localized and canonical orbitals shows that the SSCCs are driven by changes in the s-character of the natural atomic orbitals of Pt atoms, which affect the 'Fermi contact' mechanism. [ABSTRACT FROM AUTHOR]

Microreactor technology is increasingly applied in the chemical‐pharmaceutical industry for safer and more efficient drug production as compared to the traditional batch process. This technology is employed for the first time to study the production of 2‐[methyl(pyridin‐2‐yl)amino]ethanol, the first intermediate in rosiglitazone synthesis. Under the optimum operating conditions, a single microreactor chip at 160 °C allowed to produce the equivalent of more than five batch reactors at 120 °C. The kinetic study indicated that the reaction is second order. Thermodynamic parameters were determined by the Eyring equation and density functional theory (DFT) calculations with good agreement. DFT results suggested a concerted nucleophilic aromatic substitution reaction mechanism. [ABSTRACT FROM AUTHOR]