Search results for "DFT"

The Right Answer for the Right Electrostatics: Force Field Methods Are Able to Describe Relative Energies of DNA Guanine Quadruplexes

2014

Different force fields and approximate density functional theory were applied in order to study the rotamer space of the telomeric G-quadruplex DNA. While some force fields show an erratic behavior when it comes to the reproduction of the higher-order DNA conformer space, OPLS and MMFF implementations are able to reproduce the experimentally known energy order. The stabilizing effect of the AA (anti−anti) versus SA (syn−anti) conformer is analyzed applying mechanical bond strength descriptors (compliance constants). The fact that we observe the correct energy order using appropriate force fields is in contrast with results previously reported, which suggested the general inappropriateness o…

Carbon–Phosphorus Coupling from C^N Cyclometalated Au III Complexes

2020

Abstract With the aim of exploiting new organometallic species for cross‐coupling reactions, we report here on the AuIII‐mediated Caryl−P bond formation occurring upon reaction of C^N cyclometalated AuIII complexes with phosphines. The [Au(C^N)Cl2] complex 1 featuring the bidentate 2‐benzoylpyridine (CCON) scaffold was found to react with PTA (1,3,5‐triaza‐7‐phosphaadamantane) under mild conditions, including in water, to afford the corresponding phosphonium 5 through C−P reductive elimination. A mechanism is proposed for the title reaction based on in situ 31P{1H} NMR and HR‐ESI‐MS analyses combined with DFT calculations. The C−P coupling has been generalized to other C^N cyclometalated Au…

New light on an old debate: Does the RCN-PtCl2 bond include any back-donation? RCN←PtCl2 backbonding: Vs. the IR ν CN blue-shift dichotomy in organon…

2019

For a series of organonitrile [RCN (R = Me, CF3, Ph, CH3Ph, CF3Ph)] ligands, the nature of the N-Pt bond in the related cis-/trans-(RCN)2PtCl2 complexes has been computationally investigated by Density Functional Theory. A fragment based bond analysis has been performed in the canonical Kohn-Sham molecular orbitals framework, and it has been ultimately assessed that this bond is characterized both by N→Pt σ and by N←Pt π contributions. Voronoi Deformation Density charges further confirms the occurrence of N←Pt π interactions. Moreover, the Energy Decomposition Analysis-Natural Orbital for Chemical Valence (EDA-NOCV) method shows that the strength of the N←Pt π interaction is not negligible …

Structure Sensitivity of 2‐Methyl--butyn-2-ol Hydrogenation on Pd: Computational and Experimental Modeling

2014

Growth of Palladium Clusters on a Boron Nitride Nanotube Support

2015

We demonstrated that the migration process of a single palladium atom on the BNNT is not highly energy demanding and can be represented as a hopping mechanism between boron and nitrogen. A model was finally found for the interpretation of the growth energetics, showing that the process is generally favoured increasing the cluster size.

Integrated experimental and theoretical study on the phase transition and photoluminescent properties of ZrO2:xTb3+ (x=1, 2, 4 and 8 mol %)

2021

Abstract Zirconia (ZrO2) has been intensively studied as an important ceramic material, and numerous technological applications have been found. The present work deals with synthesizing and characterizing the phase transition (cubic vs tetragonal) and photoluminescence emissions of ZrO2:xTb3+ (x = 1,2,4 and 8 mol%). The samples formed by the complex polymerization were thoroughly characterized for physicochemical properties such powder by X-ray diffraction (XRD), and Raman and diffuse reflectance spectroscopies. First-principle calculations at the density functional theory level were performed to complement and rationalize the experimental results. An energy transfer mechanism which promote…

Vibrational Analysis of Paraelectric–Ferroelectric Transition of LiNbO3: An Ab-Initio Quantum Mechanical Treatment

2021

FSG acknowledges the CINECA award under the ISCRA initiative (HP10BJO47B) for the availability of high-performance computing resources and support.

Photochemical intermediates of trans-Rh(CO)L2Cl where L=PMe3, PBu3, and i-Pr2HN and cis-Rh(CO)2(i-Pr2HN)Cl in frozen organic glasses

2002

International audience; The Nujol glass matrix photolyses of Rh(CO)(PMe3)2Cl (1), Rh(CO)(PBu3)2Cl (2), Rh(CO)2(i-Pr2HN)Cl (3), and Rh(CO)(i-Pr2HN)2Cl (4), have been examined. Phototolysis of 1 (λirr>400 nm) and 2 (350<λirr<400 nm) give new species, A, with carbonyl stretching bands slightly below the parent bands. In the case of 1 this species appears to give rise to a second product, C, upon either extended photolysis or annealing. High-energy photolysis of 1, 2, and 4, result in loss of CO and formation of an IR silent species, RhL2Cl. In the case of 1 a new carbonyl species, B, is observed upon high-energy photolysis or annealing of a matrix containing CO and Rh(PMe3)2Cl. B may be conver…

Detekcia vektora spinovej polarizácie vo viackanálovej spinovo rozlýšenej fotoemissie za použitia spinového filtra založeného na Ir(001)

2016

Physical review / B 95(10), 104423 (2017). doi:10.1103/PhysRevB.95.104423

X-ray Crystal Structure and Hirshfeld Analysis of Gem-Aminals-Based Morpholine, Pyrrolidine, and Piperidine Moieties

2020

The gem-aminals of 1,2-dimorpholinoethane (1) and 1-morpholino-3-morpholinium bromide propane (2) were synthesized by reaction of two molar ratio of morpholine with the halogenating agents in the presence of basic condition (K2CO3) in acetone at room temperature (RT) overnight. The structures of the centro-symmetric compound 1 and the morpholinium salt derivative 2 were assigned unambiguous by single crystal X-ray diffraction analysis and compared with the 1,2-di(pyrrolidin-1-yl)ethane 3 and 1,2-di(piperidin-1-yl)ethane 4. The 1,2-dimorpholinoethane molecule has a center of symmetry at the midpoint of the C-C bond of the ethyl moiety leading to two equivalent halves. It crystallized in mono…