Search results for "D-"
showing 10 items of 12236 documents
Hexacarbonyls of Mo, W, and Sg: Metal–CO Bonding Revisited
2017
Calculations of the first bond dissociation energies (FBDEs) and other molecular properties of M(CO)6, where M = Mo, W, and Sg, have been performed using a variety of nonrelativistic and relativistic methods, such as ZORA-DFT, X2c+AMFI-CCSD(T), and Dirac–Coulomb density functional theory. The aim of the study is to assist experiments on the measurements of the FBDE of Sg(CO)6. We have found that, different from the results published earlier, the metal–CO bond in Sg(CO)6 should be weaker than that in W(CO)6. A comparison of the relativistic and nonrelativistic FBDE values, as well as molecular orbital and vibrational frequency analyses within both the nonrelativistic and relativistic approac…
Bond Dissociation Energies for Diatomic Molecules Containing 3d Transition Metals: Benchmark Scalar-Relativistic Coupled-Cluster Calculations for 20 …
2017
Benchmark scalar-relativistic coupled-cluster calculations for dissociation energies of the 20 diatomic molecules containing 3d transition metals in the 3dMLBE20 database ( J. Chem. Theory Comput. 2015 , 11 , 2036 ) are reported. Electron correlation and basis set effects are systematically studied. The agreement between theory and experiment is in general satisfactory. For a subset of 16 molecules, the standard deviation between computational and experimental values is 9 kJ/mol with the maximum deviation being 15 kJ/mol. The discrepancies between theory and experiment remain substantial (more than 20 kJ/mol) for VH, CrH, CoH, and FeH. To explore the source of the latter discrepancies, the …
Nonlinear response theory for Markov processes II: Fifth-order response functions
2017
The nonlinear response of stochastic models obeying a master equation is calculated up to fifth-order in the external field thus extending the third-order results obtained earlier (G. Diezemann, Phys. Rev. E{\bf 85}, 051502 (2012)). For sinusoidal fields the $5\om$-component of the susceptibility is computed for the model of dipole reorientations in an asymmetric double well potential and for a trap model with a Gaussian density of states. For most realizations of the models a hump is found in the higher-order susceptibilities. In particular, for the asymmetric double well potential model there are two characteristic temperature regimes showing the occurence of such a hump as compared to a …
Carbonyl compounds of Tc, Re, and Bh: Electronic structure, bonding, and volatility.
2018
Calculations of molecular properties of M(CO)5 and MH(CO)5, where M = Tc, Re, and Bh, and of the products of their decomposition, M(CO)4 and MH(CO)4, were performed using density functional theory and coupled-cluster methods implemented in the relativistic program suits such as ADF, DIRAC, and ReSpect. The calculated first M—CO bond dissociation energies (FBDEs) of Bh(CO)5 and BhH(CO)5 turned out to be significantly weaker than those of the corresponding Re homologs. The reason for that is the relativistic destabilization and expansion of the 6d AOs, responsible for weaker σ-forth and π-back donations in the Bh compounds. The relativistic FBDEs of M(CO)5 have, therefore, a Λ-shape behavior …
Pressure‐induced widths and shifts for the ν3 band of methane
1994
International audience; Widths and shifts of methane lines perturbed by nitrogen are calculated using a complex-valued implementation of Robert-Bonamy (RB) theory. The static intermolecular potential is described as a sum of electrostatic forces and Lennard-Jones (6-12) atom-atom terms, using literature values for all physical parameters. Vibrational dependence of the isotropic potential is obtained from the polarizability of methane assuming a dispersion interaction. The repulsive part of the Lennard-Jones accounts for the greatest part of widths, while dispersion interactions are largely responsible for shifts. Although the average error between calculated and observed linewidths (up to J…
Estimation des incertitudes de mesure sur bras polyarticulé portable par méthode de Monte Carlo
2013
International audience; Les bras polyarticulés portables ont progressivement évolué et sont de plus en plus utilisés dans l’industrie. Cependant, à l’heure actuelle, la traçabilité de ces dispositifs est difficile à effectuer et les incertitudes de mesures relatives à l’utilisation de ces appareils ne sont pas quantifiées. Le travail mené consiste à déterminer les incertitudes de mesures associées à la quantification, par un bras polyarticulé portable, des caractéristiques géométriques et dimensionnelles d’une pièce mécanique. Les travaux visant à élaborer un modèle d’incertitude de mesure, sont basés sur la méthode de Monte Carlo du supplément 1 du Guide pour l'expression de l'incertitude …
The first example of cofacial bis(dipyrrins)
2016
International audience; Two series of cofacial bis(dipyrrins) were prepared and their photophysical properties as well as their bimolecular fluorescence quenching with C-60 were investigated. DFT and TDDFT computations were also performed as a modeling tool to address the nature of the fluorescence state and the possible inter-chromophore interactions. Clearly, there is no evidence for such interactions and the bimolecular quenching of fluorescence, in comparison with mono-dipyrrins, indicates that C-60-bis(dipyrrin) contacts occur from the outside of the "mouth" of the cofacial structure.
Ring opening polymerization of d,l-lactide and ε-caprolactone catalysed by (pyrazol-1-yl)copper(ii) carboxylate complexes
2021
1,2-Bis{(3,5-dimethylpyrazol-1-yl)methyl}benzene (L) reacts with [Cu(OAc)2] and C6H5COOH, 4-OH-C6H4COOH, 2-Cl-C6H4COOH and (3,5-NO2)2-C6H3COOH to afford the copper complexes [Cu2(C6H5COO)4(L)2] (1), [Cu2(4-OH-C6H4COO)4(L)2] (2), [Cu2(2-Cl-C6H4COO)4(L)2]n (3) and [Cu{(3,5-NO2)2-C6H3COO}2L]n (4) which are characterised by IR, mass spectrometry, elemental analyses, and X-ray crystallography. The structural data revealed two geometries that are adopted by the complexes: (i) paddle wheel in 1, 2·7H2O, 3 and (ii) regular chains in 3 and 4. Magnetic studies show strong antiferromagnetic couplings in the paddle wheel complexes and a weak antiferromagnetic coupling in the monometallic chain one. Cat…
Structural Tuning and Conformational Stability of Aromatic Oligoamide Foldamers
2017
A series of aromatic oligoamide foldamers with two or three pyridine-2,6-dicarboxamide units as their main folding motifs and varying aromatic building blocks as linkers have been synthetized to study the effects of the structural variation on the folding properties and conformational stability. Crystallographic studies showed that in the solid state the central linker unit either elongates the helices and more open S-shaped conformations, compresses the helices to more compact conformations or acts as a rigid spacer separating the pyridine-2,6-dicarboxamide units, which for their part add the predictability of the conformational properties. Multidimensional NMR studies showed that, even in…
A new hydrogen bonding motif involved in self-recognition in the solid state by functionalised macrocycles
2011
Self-recognition within the crystal lattices of three functionalised macrocycles results in the formation of arrays of remarkably similar hermaphroditic pairs of macrocycles. In the case of two of the macrocycles containing acylhydrazine substituents, a hitherto unknown recognition pattern is found in the interaction of the hydrazine moiety with crown-ether oxygen atoms.