Search results for "DFT"

Computational modelling of boron nitride nanostructures based on density-functional tight-binding

2014

Boorinitridin (BN) nanorakenteet ovat sekä rakenteellisesti että lujuusominaisuuksiensa puolesta hyvin samankaltaisia vastaavien hiilirakenteiden kanssa. Suurimpana erona on BN:n sähköinen eristävyys kun taas hiilirakenteet ovat johteita tai puolijohteita. BN onkin hyvin lupaava nanomateriaali ja sille on odotettavissa sovelluksia muun muassa muiden nanorakenteiden suojaajana ja komposiittimateriaalien nanokudosaineena. BN:n nanorakenteiden ominaisuuksia tutkitaan laskennallisesti yleensä joko tiheysfunktionaaliteorialla (DFT) tai tiukan sidoksen (TB) malleilla. Ensin mainittu on tarkka mutta laskennallisesti vaativa, kun taas jälkimmäinen on laskennallisesti kevyt mutta epätarkka. Tässä ty…

Diorganotin(IV) N-acetyl-L-cysteinate complexes: synthesis, solid state, solution phase, DFT and biological investigations.

2009

Diorganotin(IV) complexes of N-acetyl-L-cysteine (H(2)NAC; (R)-2-acetamido-3-sulfanylpropanoic acid) have been synthesized and their solid and solution-phase structural configurations investigated by FTIR, Mössbauer, (1)H, (13)C and (119)Sn NMR spectroscopy. FTIR results suggested that in R(2)Sn(IV)NAC (R = Me, Bu, Ph) complexes NAC(2-) behaves as dianionic tridentate ligand coordinating the tin(IV) atom, through ester-type carboxylate, acetate carbonyl oxygen atom and the deprotonated thiolate group. From (119)Sn Mössbauer spectroscopy it could be inferred that the tin atom is pentacoordinated, with equatorial R(2)Sn(IV) trigonal bipyramidal configuration. In DMSO-d(6) solution, NMR spectr…

Biogenic Selenium Nanoparticles: A Fine Characterization to Unveil Their Thermodynamic Stability

2021

Among the plethora of available metal(loid) nanomaterials (NMs), those containing selenium are interesting from an applicative perspective, due to their high biocompatibility. Microorganisms capable of coping with toxic Se-oxyanions generate mostly Se nanoparticles (SeNPs), representing an ideal and green alternative over the chemogenic synthesis to obtain thermodynamically stable NMs. However, their structural characterization, in terms of biomolecules and interactions stabilizing the biogenic colloidal solution, is still a black hole that impairs the exploitation of biogenic SeNP full potential. Here, spherical and thermodynamically stable SeNPs were produced by a metal(loid) tolerant Mic…

Donation and back-donation in cis- and trans-[(η5-C5H5)Fe(η1-CO)(μ-CO)]2 tautomers: Which relative is more generous? An ETS-NOCV bond analysis

2022

The ETS-NOCV bond analysis has been exploited to quantitatively estimate donation and back-donation properties of [(η5-C5H5)]−, CO, and FeI in the cis-/trans-[(η5-C5H5)Fe(η1-CO)(μ-CO)]2 (cis-I/trans-I) tautomers. Theoretical outcomes indicate that the Fe-CO bond, regardless to the CO monoapto (η1-) or bridging (μ-) coordination, has a sizeable π Fe → CO back-bonding contribution, which is stronger in trans-I than in cis-I. Moreover, [(η5-C5H5)]− has the weakest back-donation acceptor capability. The back-bonding behaviour of the Fe → η1-CO interaction well agrees with the experimental symmetric/antisymmetric infrared νCO (sνηjavax.xml.bind.JAXBElement@fc12185-CO/aνηjavax.xml.bind.JAXBElemen…

Matrix isolation studies and DFT calculations on molecular alkali metal bromates

2009

DFT and MP2 calculations have been carried out on a series of molecular alkali metal bromates MBrO3 (M = Na, K, Rb, Cs), and the results compared with matrix isolation IR studies on the vaporisation of the solid salts. For M = Na, K or Rb, no ternary molecular species were detected in the low temperature matrix, but vaporisation of solid caesium bromate at 730 K resulted in the formation of molecular CsBrO3, which was identified as having a C3v structure involving tridentate coordination. Additionally, the DFT and MP2 calculations provide estimates of the molecular parameters for all four MBrO3 species, and for the related MXO3 species CsClO3 and CsIO3. The proven stability of MBrO3 molecul…

Spectroscopic, crystal structural, theoretical and biological studies of phenylacetohydrazide Schiff base derivatives and their copper complexes

2020

Two phenylacetohydrazide Schiff base derivatives: N’-(1-(2-hydroxyphenyl)ethylidene)-2-phenylacetohydrazide, HL1, and N’-((1-hydroxynaphthalen-2-yl)methylene)-2-phenylacetohydrazide, HL2, were synthesized. HL1 dimerizes in presence of HCl, probably via radical mechanism to give (2,2’-((1E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))diphenol (DIM). Thermal reactions of Cu(II) ions with the two Schiff base ligands resulted in formation of the binuclear complexes [(CuL1)2] and [(CuL2)2]. The stoichiometry and structures of the reported compounds were investigated by several spectroscopic and analytical techniques. The structure of the HL1 ligand and its complex [(CuL1)2] as well as the D…

DFT calculation of 1J(119Sn,13C) and 2J(119Sn,1H) coupling constants in di- and trimethyltin(IV) compounds

2008

We have tested several computational protocols, at the nonrelativistic DFT level of theory, for the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) spin-spin coupling constants in di- and trimethyltin(IV) derivatives with various ligands. Quite a good agreement with experimental data has been found with several hybrid functionals and a double-zeta basis set for a set of molecules comprising tetra-, penta-, and hexa-coordinated tin(IV). Then, some of the protocols have been applied to the calculation of the 2J(119Sn, 1H) of the aquodimethyltin(IV) ion and dimethyltin(IV) complex with D-ribonic acid and to the calculation of 1J(119Sn, 13C) and 2J(119Sn, 1H) of the dimethyltin(IV)-glycylglycin…

Effect of electron-withdrawing substituents on the electrophilicity of carbonyl carbons

2005

Indexación: Scopus The substituent effects on the carbonyl carbon atom for a series of twelve substituted phenyl acetates have been rationalized using a global electrophilicity index. This index is linearly correlated with the experimental reaction rate coefficients. We found that, in contrast to the proposed interpretation based on experimental 13C NMR chemical shifts and ground state destabilization calculations, the electrophilicity of carbonyl compounds increases due to the effect promoted by electron-withdrawing groups in these systems. https://www.sciencedirect.com/science/article/pii/S0040402004018046?via%3Dihub

Modeled Catalytic Properties of MOF-Based Compounds” in “Metal-Organic Frameworks: Materials Modeling Towards Potential Engineering Applications

2015

Anion-driven encapsulation of cationic guests inside pyridine[4]arene dimers

2019

Pyridine[4]arenes have previously been considered as anion binding hosts due to the electron-poor nature of the pyridine ring. Herein, we demonstrate the encapsulation of Me4N+ cations inside a dimeric hydrogen-bonded pyridine[4]arene capsule, which contradicts with earlier assumptions. The complexation of a cationic guest inside the pyridine[4]arene dimer has been detected and studied by multiple gas-phase techniques, ESI-QTOF-MS, IRMPD, and DT-IMMS experiments, as well as DFT calculations. The comparison of classical resorcinarenes with pyridinearenes by MS and NMR experiments reveals clear differences in their host–guest chemistry and implies that cation encapsulation in pyridine[4]arene…