Showing papers by "Jan M. L. Martin published in 2010"
TL;DR: In this paper, a general-purpose double-hybrid DFT parametrization based on the BLYP functional, spin-component scaled (SCS) MP2-like correlation and a dispersion correction, called DSD-BLYP, is presented.
Abstract: We present a general purpose double-hybrid DFT parametrization based on the BLYP functional, spin-component scaled (SCS) MP2-like correlation and a dispersion correction, called DSD-BLYP. Six train...
320 citations
TL;DR: A polyoxometalate of the Keggin structure substituted with Ru(III), (6)Q(5)[Ru(III)(H(2)O)SiW(11)O(39)] catalyzed the photoreduction of CO( 2) to CO with tertiary amines, preferentially Et(3)N, as reducing agents.
Abstract: A polyoxometalate of the Keggin structure substituted with Ru(III), (6)Q(5)[Ru(III)(H(2)O)SiW(11)O(39)] in which (6)Q=(C(6)H(13))(4)N(+), catalyzed the photoreduction of CO(2) to CO with tertiary amines, preferentially Et(3)N, as reducing agents. A study of the coordination of CO(2) to (6)Q(5)[Ru(III)(H(2)O)SiW(11)O(39)] showed that 1) upon addition of CO(2) the UV/Vis spectrum changed, 2) a rhombic signal was obtained in the EPR spectrum (g(x)=2.146, g(y)=2.100, and g(z)=1.935), and 3) the (13)C NMR spectrum had a broadened peak of bound CO(2) at 105.78 ppm (Delta(1/2)=122 Hz). It was concluded that CO(2) coordinates to the Ru(III) active site in both the presence and absence of Et(3)N to yield (6)Q(5)[Ru(III)(CO(2))SiW(11)O(39)]. Electrochemical measurements showed the reduction of Ru(III) to Ru(II) in (6)Q(5)[Ru(III)(CO(2))SiW(11)O(39)] at -0.31 V versus SCE, but no such reduction was observed for (6)Q(5)[Ru(III)(H(2)O)SiW(11)O(39)]. DFT-calculated geometries optimized at the M06/PC1//PBE/AUG-PC1//PBE/PC1-DF level of theory showed that CO(2) is preferably coordinated in a side-on manner to Ru(III) in the polyoxometalate through formation of a Ru-O bond, further stabilized by the interaction of the electrophilic carbon atom of CO(2) to an oxygen atom of the polyoxometalate. The end-on CO(2) bonding to Ru(III) is energetically less favorable but CO(2) is considerably bent, thus favoring nucleophilic attack at the carbon atom and thereby stabilizing the carbon sp(2) hybridization state. Formation of a O(2)C-NMe(3) zwitterion, in turn, causes bending of CO(2) and enhances the carbon sp(2) hybridization. The synergetic effect of these two interactions stabilizes both Ru-O and C-N interactions and probably determines the promotional effect of an amine on the activation of CO(2) by [Ru(III)(H(2)O)SiW(11)O(39)](5-). Electronic structure analysis showed that the polyoxometalate takes part in the activation of both CO(2) and Et(3)N. A mechanistic pathway for photoreduction of CO(2) is suggested based on the experimental and computed results.
126 citations
TL;DR: The analysis of charge- and spin-density distributions shows that spin delocalization in the boryl radical complexes constitutes one of the mechanisms of radical stabilization.
Abstract: Radical stabilization energies (RSE)s have been calculated for a variety of boryl radicals complexed to Lewis bases at the G3(MP2)-RAD level of theory. These are referenced to the B-H bond dissociation energy (BDE) in BH(3) determined at W4.3 level. High RSE values (and thus low BDE(B-H) values) have been found for borane complexes of a variety of five- and six-membered ring heterocycles. Variations of RSE values have been correlated with the strength of Lewis acid-Lewis base complex formation at the boryl radical stage. The analysis of charge- and spin-density distributions shows that spin delocalization in the boryl radical complexes constitutes one of the mechanisms of radical stabilization.
73 citations
TL;DR: It is found that post-CCSD(T) contributions are essential to achieve such narrow confidence intervals for r(e) and ω(e), but have little effect on ω (e)x(e).
Abstract: Accurate spectroscopic constants and electrical properties of small molecules are determined by means of W4 and post-W4 theories. For a set of 28 first- and second-row diatomic molecules for which very accurate experimental spectroscopic constants are available, W4 theory affords near-spectroscopic or better predictions. Specifically, the root-mean-square deviations (RMSDs) from experiment are 0.04 pm for the equilibrium bond distances (re), 1.03 cm−1 for the harmonic frequencies (ωe), 0.20 cm−1 for the first anharmonicity constants (ωexe), 0.10 cm−1 for the second anharmonicity constants (ωeye), and 0.001 cm−1 for the vibration-rotation coupling constants (αe). These RMSDs imply 95% confidence intervals of about 0.1 pm for re, 2.0 cm−1 for ωe, 0.4 cm−1 for ωexe, and 0.2 cm−1 for ωeye. We find that post-CCSD(T) contributions are essential to achieve such narrow confidence intervals for re and ωe, but have little effect on ωexe and αe, and virtually none on ωeye. Higher-order connected triples T3−(T) impr...
67 citations
TL;DR: An extensive DFT study of the Pt-oxo bonding is reported, revealing that one solvent molecule is weakly coordinated to the complex in acetone solution, and that low affinity of the terminal oxo ligand toward "soft" covalent interactions brings about intermediate formation of agostic hydrido and hydroxo complexes along the reaction pathway of dihydrogen oxidation.
Abstract: The recently published [(PCN)Pt═O](+) complex is interesting as a unique example of a stable d(6) terminal transition metal oxo complex not stabilized by electron withdrawing ligands and as a model of oxo complexes frequently implicated as key intermediates in various processes of oxygen transfer. In the present work, we report an extensive DFT study of its geometric and electronic structure, composition in solution, and reactivity. The thermodynamic data and calculated (195)Pt NMR chemical shifts reveal that one solvent molecule is weakly coordinated to the complex in acetone solution. This ancillary ligand is responsible for the diamagnetic state of the complex, retards intramolecular oxygen transfer, and facilitates CO oxidation. Chemical transformations of the coordinated acetone molecule, coordination of other ancillary ligands present in the reaction mixture, and protonation of the Pt-oxo group in nonacidic media are excluded based on thermodynamic or kinetic considerations. Bonding of the terminal oxo ligand with strong electrophiles presents the key interaction in the mechanisms of intramolecular oxygen insertion into the Pt-P bond, in CO oxidation and in water activation mediated by microsolvation. Low affinity of the terminal oxo ligand toward "soft" covalent interactions brings about intermediate formation of agostic hydrido and hydroxo complexes along the reaction pathway of dihydrogen oxidation. Stabilization of the Pt-oxo bonding is attributed to bending of the terminal oxo ligand out of the plane of the complex and to significant transfer of electron density from compact low lying Pt 5d orbitals to more diffuse 6s and 6p orbitals.
46 citations
TL;DR: It is concluded that the fairly small modified 6‐31+G* basis set due to Pulay represents a good compromise between accuracy and efficiency, followed by Balabanov and Peterson's all‐electron aug‐cc‐pVDZ basis set.
Abstract: The coordination number of various experimentally known Cu(I) compounds is studied using density functional theory. Various basis sets are tested, aiming to establish a reliable level for prediction of the coordination number of these and other Cu(I) complexes. It is found that most levels exhibit correct trends, namely, the bulkier ligands demonstrate larger preference for coordination of two ligands. Proper absolute values are obtained when dispersion corrections are also included in the calculations. It is concluded that the fairly small modified 6-31+G* basis set due to Pulay represents a good compromise between accuracy and efficiency, followed by Balabanov and Peterson's all-electron aug-cc-pVDZ basis set. The overall energy is decomposed into various components whose relative contribution to the overall tendency of forming a complex with a particular coordination is examined. It is shown that two opposing contributions play a major role: the interaction energy of the ligand being added and the deformation energy of the copper's coordination sphere prior to the ligand addition. The former being a stabilizing contribution, leads to higher coordination numbers while the later, a destabilizing contribution, is shown to favor lower coordination numbers. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010
21 citations
TL;DR: In this article, a set of 28 first and second-row diatomic molecules for which very accurate experimental spectroscopic constants are available are determined by means of W4 and post-W4 theories.
Abstract: Accurate spectroscopic constants and electrical properties of small molecules are determined by means of W4 and post-W4 theories. For a set of 28 first- and second-row diatomic molecules for which very accurate experimental spectroscopic constants are available, W4 theory affords near-spectroscopic or better predictions. Specifically, the root-mean-square deviations (RMSD) from experiment are 0.04 pm for the equilibrium bond distances (r_e), 1.03 cm^{-1} for the harmonic frequencies (\omega_e), 0.20 cm^{-1} for the first anharmonicity constants (\omega_e x_e), 0.10 cm^{-1} for the second anharmonicity constants (\omega_e y_e), and 0.001 cm^{-1} for the vibration-rotation coupling constants (\alpha_e). Higher-order connected triples, \hat{T}_3-(T), improve agreement with experiment for the hydride systems, but their inclusion (in the absence of \hat{T}_4) tends to worsen agreement with experiment for the nonhydride systems. Connected quadruple excitations, \hat{T}_4, have significant and systematic effects on r_e, \omega_e, and \omega_e x_e, in particular they universally increase r_e (by up to 0.5 pm), universally reduce \omega_e (by up to 32 cm^{-1}), and universally increase \omega_e x_e (by up to 1 cm^{-1}). Connected quintuple excitations, \hat{T}_5, are spectroscopically significant for \omega_e of the nonhydride systems, affecting \omega_e by up to 4 cm^{-1}. The triatomic molecules H_2O, CO_2, and O_3, as well as the pathologically multireference BN and BeO diatomics, are also considered. The asymmetric stretch of ozone represents a severe challenge to W4 theory, in particular the connected quadruple contribution converges very slowly with the basis set size. Finally, the importance of post-CCSD(T) correlation effects for electrical properties, namely dipole moments (\mu), polarizabilities (\alpha), and first hyperpolarizabilities (\beta) is evaluated.
3 citations
2 citations