Search results for "Density Functional Theory"
showing 10 items of 981 documents
The Importance of Electronic Dimensionality in Multiorbital Radical Conductors.
2019
The exceptional performance of oxobenzene-bridged bis-1,2,3-dithiazolyls 6 as single-component neutral radical conductors arises from the presence of a low-lying π-lowest unoccupied molecular orbital, which reduces the potential barrier to charge transport and increases the kinetic stabilization energy of the metallic state. As part of ongoing efforts to modify the solid-state structures and transport properties of these so-called multiorbital materials, we report the preparation and characterization of the acetoxy, methoxy, and thiomethyl derivatives 6 (R = OAc, OMe, SMe). The crystal structures are based on ribbonlike arrays of radicals laced together by S···N' and S···O' secondary bondin…
Iron(III) bis(pyrazol-1-yl)acetate based decanuclear metallacycles: synthesis, structure, magnetic properties and DFT calculations
2016
The synthesis, structural aspects, magnetic interpretation and theoretical rationalizations for a new member of the ferric wheel family, a decanuclear iron(III) complex with the formula [Fe10(bdtbpza)10(μ2-OCH3)20] (1), featuring the N,N,O tridentate bis(3,5-di-tert-butylpyrazol-1-yl)acetate ligand, are reported. The influence of the steric effect on both the core geometry and coordination mode is observed. Temperature dependent (2.0–300 K range) magnetic susceptibility studies carried out on complexes 1 established unequivocally antiferromagnetic (AF) interactions between high-spin iron(III) centers (S = 5/2), leading to a ground state S = 0. The mechanism of AF intramolecular coupling was…
Understanding the molecular mechanism of the [3 + 2] cycloaddition reaction of benzonitrile oxide toward electron-richN-vinylpyrrole: a DFT study
2016
The [3 + 2] cycloaddition (32CA) reaction of benzonitrile oxide, BNO 2, with an electron-rich N-vinylpyrrole derivative, NVP 3a, in the presence of dichloromethane, has been theoretically studied using density functional theory (DFT) methods at the B3LYP/6-31G(d) level. This 32CA reaction presents a relatively high activation Gibbs free energy as a result of the low polar character of this zwitterionic-type (zw-type) reaction. Analyses of the calculated relative Gibbs free energies and transition state geometries indicate that the studied 32CA reaction, in excellent agreement with experimental outcomes, takes place in a complete regioselective manner as a consequence of the steric repulsion…
Stability of Dinuclear Phosphane Palladium(III) Complexes: A DFT Approach
2018
Computational density functional theory studies have been carried out for the dinuclear ortho-metalated palladium(III) compounds [Pd2{μ-(C6H4)PPh2}2{μ-(X1-X2)}2Cl2]. These studies have shown that the electronic and steric properties of the auxiliary ligands (X1-X2 = bridging (carboxylato) or chelating (phenolato/acetylacetonato) O,O-donor ligands, bridging N,N-donor ligands (triazenido/formamidinato/pyrazolato), and bridging N,S-donor ligands) lead to systematic trends in their stability, highlighting that (a) the electronic nature of the donor atoms trans to the P has a clear trend, the replacement of hard donor atoms (O, N) by softer S donors generally reducing the stability of the compou…
A Density Functional Study of Open-Shell Cyclopentadienyl−Molybdenum(II) Complexes. A Comparison of Stabilizing Factors: Spin-Pairing, Mo−X π Bonding…
2000
International audience; The dissociation of PH3 from the 18-electron system CpMoX(PH3)3 to afford the corresponding 16-electron CpMoX(PH3)2 fragment has been investigated theoretically by density functional theory for X = H, CH3, F, Cl, Br, I, OH, and PH2. The product is found to prefer a triplet spin state for all X ligands except PH2, the singlet−triplet gap varying between 1.7 kcal/mol for OH to 8.7 kcal/mol for F. The Mo−PH3 bond dissociation energy to the 16-electron ground state varies dramatically across the series, from 4.5 kcal/mol for OH to 23.5 kcal/mol for H, and correlates with experimental observations on trisubstituted phosphine derivatives. Geometry-optimized spin doublet Cp…
Dinitrogen complexation with main group radicals
2011
In this report we present data from hyperfine sublevel correlation spectroscopy (HYSCORE), an electron paramagnetic resonance (EPR) spectroscopic technique, that reveals weak but distinct interactions between several main group element radicals and physically dissolved dinitrogen in solution. These interactions are the basis for a well-defined coordination of N2 to the paramagnetic centers. The complexes formed are primarily of the van der Waals-type but also feature a non-negligible orbital overlap between dinitrogen and the radicals' SOMO. Our spectroscopic findings are strongly supported by experiments with isotope-labeled 15N2, spectral simulations and quantum chemical and density funct…
A density functional theory study of uranium(VI) nitrate monoamide complexes.
2011
Density functional theory calculations were performed on uranyl complexed with nitrate and monoamide ligands (L) [UO(2)(NO(3))(2)·2L]. The obtained results show that the complex stability is mainly governed by two factors: (i) the maximization of the polarizability of the coordinating ligand and (ii) the minimization of the steric hindrance effects. Furthermore, the electrostatic interaction between ligands and uranium(vi) was found to be a crucial parameter for the complex stability. These results pave the way to the definition of (quantitative) property/structure relationships for the in silico screening of monoamide ligands with improved extraction efficiency of uranium(vi) in nitrate ac…
Probing the non-innocent nature of an amino-functionalised β-diketiminate ligand in silylene/iminosilane systems.
2020
Electron-rich β-diketiminate ligands, featuring amino groups at the backbone β positions (“N-nacnac” ligands) have been employed in the synthesis of a range of silylene (SiII) complexes of the type (N-nacnac)SiX (where X = H, Cl, N(SiMe3)2, P(SiMe3)2 and Si(SiMe3)3). A combination of experimental and quantum chemical approaches reveals (i) that in all cases rearrangement to give an aza-butadienyl SiIV imide featuring a contracted five-membered heterocycle is thermodynamically favourable (and experimentally viable); (ii) that the kinetic lability of systems of the type (N-nacnac)SiX varies markedly as a function of X, such that compounds of this type can be isolated under ambient conditions …
A unified view of ligand-protected gold clusters as superatom complexes
2008
Synthesis, characterization, and functionalization of self-assembled, ligand-stabilized gold nanoparticles are long-standing issues in the chemistry of nanomaterials. Factors driving the thermodynamic stability of well documented discrete sizes are largely unknown. Herein, we provide a unified view of principles that underlie the stability of particles protected by thiolate (SR) or phosphine and halide (PR 3 , X) ligands. The picture has emerged from analysis of large-scale density functional theory calculations of structurally characterized compounds, namely Au 102 (SR) 44 , Au 39 (PR 3 ) 14 X 6 − , Au 11 (PR 3 ) 7 X 3 , and Au 13 (PR 3 ) 10 X 2 3+ , where X is either a halogen or a thiol…
Phosphane tuning in heteroleptic [Cu(N^N)(P^P)]+ complexes for light-emitting electrochemical cells
2019
The synthesis and characterization of five [Cu(P^P)(N^N)][PF 6 ] complexes in which P^P = 2,7-bis( tert -butyl)-4,5-bis(diphenylphosphino)-9,9-dimethylxanthene ( t Bu 2 xantphos) or the chiral 4,5-bis(mesitylphenylphosphino)-9,9-dimethylxanthene (xantphosMes 2 ) and N^N = 2,2'-bipyridine (bpy), 6-methyl-2,2'-bipyridine (6-Mebpy) or 6,6'-dimethyl-2,2'-bipyridine (6,6'-Me 2 bpy) are reported. Single crystal structures of four of the compounds confirm that the copper(I) centre is in a distorted tetrahedral environment. In [Cu(xantphosMes 2 )(6-Mebpy)][PF 6 ], the 6-Mebpy unit is disordered over two equally populated orientations and this disorder parallels a combination of two dynamic processe…