Nuclearity Expansion in Pd Clusters Triggered by the Migration of a Phenyl Group in Cyclooligosilanes

2021 ◽  
Author(s):  
Kento Shimamoto ◽  
Yusuke Sunada
Keyword(s):  
Phenyl Group ◽  
Palladium Clusters ◽  
Pd Clusters

Heptanuclear palladium clusters with six palladium atoms in a planar arrangement were obtained from the reaction of [Pd(CNtBu)2]3 with Ph-substituted cyclotetrasilane or cyclopentasilane via the migration of a phenyl group....

FORMATION OF SURFACE DIPOLES FOR SMALL PALLADIUM CLUSTERS DEPOSITED ON α-(0001)Al2O3

1996 ◽  
Vol 03 (01) ◽  
pp. 973-977 ◽  
Author(s):  
S. OGAWA ◽  
S. ICHIKAWA
Keyword(s):  
Charge Transfer ◽  
Single Crystal ◽  
Work Function ◽  
Probe Method ◽  
Kelvin Probe ◽  
Electronic Interactions ◽  
Palladium Clusters ◽  
Metal Support ◽  
Pd Clusters ◽  
Kelvin Probe Method

The Kelvin-probe method is utilized to measure the work function of a single-crystal aluminum covered with palladium clusters. It is found that formation of interface dipoles occurs by charge transfer from Al 2 O 3 to Pd clusters, particularly for those less than 2 nm in diameter. These results provide valuable clue to the understanding of metal-support electronic interactions, which is important in catalysis.

Direct UHV-TEM Observation of Palladium Clusters on a Silicon Surface

2004 ◽  
Vol 10 (1) ◽  
pp. 134-138 ◽  
Author(s):  
Masaki Takeguchi ◽  
Kazutaka Mitsuishi ◽  
Miyoko Tanaka ◽  
Kazuo Furuya
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Surface Layer ◽  
Silicon Surface ◽  
Lattice Structure ◽  
Plan View ◽  
Palladium Clusters ◽  
Transmission Electron ◽  
Pd Clusters

About 1 monolayer of palladium was deposited onto a silicon (111) 7 × 7 surface at a temperature of about 550 K inside an ultrahigh vacuum transmission electron microscope, resulting in formation of Pd2Si nanoislands and a 1 × 1 surface layer. Pd clusters created from an excess of Pd atoms on the 1 × 1 surface layer were directly observed byin situplan view high-resolution transmission electron microscopy. When an objective aperture was introduced so that electron diffractions less than 0.20 nm were filtered out, the lattice structure of the 1 × 1 surface with 0.33 nm spacing and the Pd clusters with a trimer shape were visualized. It was found that image contrast of the 1 × 1 lattice on the specific height terraces disappeared, and thereby an atomic structure of the Pd clusters was clearly observed. The appearance and disappearance of the 1 × 1 lattice was explained by the effect of the kinematical diffraction. It was identified that a Pd cluster was composed of three Pd atoms without a centered Si atom, which is consistent with the model proposed previously. The feature of the Pd clusters stuck at the surface step was also described.

scholarly journals INFLUENCE OF HALOGEN NATURE ON THE ADSORPTION ABILITY OF ARYL HALIDES ON PALLADIUM CLUSTERS

2021 ◽  
pp. 646-654
Author(s):  
Елена Сергеевна Бахвалова ◽  
Алексей Владимирович Быков ◽  
Линда Жановна Никошвили ◽  
Любовь Львовна Киви
Keyword(s):  
Density Functional ◽  
Phenylboronic Acid ◽  
Density Functional Theory Calculations ◽  
Energy Gain ◽  
Aryl Halides ◽  
Coupling Reactions ◽  
Palladium Clusters ◽  
Cross Coupling Reactions ◽  
Adsorption Energies ◽  
Pd Clusters

В данной работе методом теории функционала плотности проведен расчет энергий адсорбции бензольного кольца на маленьких кластерах Pd (состоящих из четырех или девяти атомов). Показано, что адсорбция бензола на кластерах палладия ведет к заметному выигрышу системы в энергии: -146 кДж/моль в случае Pd и -117 кДж/моль в случае Pd. Кроме того, для системы Pd * CH рассчитаны энергии адсорбции хлор-, бром- и йоданизола. Показано, что адсорбция йоданизола, характеризующаяся наибольшим выигрышем системы в энергии (-278 кДж/моль), происходит диссоциативно и безактивационно, что принципиально отличает его от хлор- и броманизола. Полученные данные могут использоваться для объяснения различий в поведении катализаторов на основе сверхсшитого полистирола в реакциях кросс-сочетания различных арилгалогенидов c фенилбороновой кислотой, а также того факта, что арилйодиды могут провоцировать образование гомогенных форм палладия. In this paper, the density functional theory calculations were carried out in order to find the adsorption energies of a benzene ring on small Pd clusters consisting of four or nine atoms. The adsorption of benzene on palladium clusters was found to result in a noticeable energy gain of the system: -146 kJ/mol in the case of Pd, and -117 kJ/mol in the case of Pd. The adsorption energies of chloro-, bromo- and iodoanisole on Pd * CH were also calculated. The adsorption of iodoanisole was characterized by the highest energy gain of the system (-278 kJ/mol) and occurred dissociatively without activation, that fundamentally distinguished it from chloro- and bromoanisole. The data obtained can be used to explain the differences in the behavior of catalysts based on hypercross-linked polystyrene in cross-coupling reactions of various aryl halides and phenylboronic acid, and also the fact that aryl iodides can favor the formation of homogeneous forms of palladium.

scholarly journals Distribution of Pd clusters on ultrathin, epitaxial TiO x films on Pt3Ti(111)

2015 ◽  
Vol 6 ◽  
pp. 2007-2014 ◽  
Author(s):  
Christian Breinlich ◽  
Maria Buchholz ◽  
Marco Moors ◽  
Tobias Pertram ◽  
Conrad Becker ◽  
...  
Keyword(s):  
Oxygen Vacancies ◽  
Oxide Phase ◽  
Second Phase ◽  
Template Effect ◽  
Palladium Clusters ◽  
Nucleation Sites ◽  
Scanning Tunnelling ◽  
Tunnelling Microscopy ◽  
Titania Films ◽  
Pd Clusters

Scanning tunnelling microscopy (STM) was used to investigate the nucleation and growth of palladium clusters on two different, ultrathin, epitaxial, titania films grown on a Pt3Ti(111) surface. The first oxide phase, z'-TiO x , is anisotropic and consists of parallel stripes separated by trenches. Defects (i.e., oxygen vacancies) in this structure are confined to these trenches and act as nucleation sites. Therefore, the Pd clusters are mostly arranged in unidirectional rows along the trenches, creating a template effect. The second phase, w'-TiO x , exhibits a hexagonal, long range, (7 × 7)R21.8°, Moiré-type superstructure with fewer and shallower defects, making the template effect less discernible.

4-Aryl-1,4-Dihydropyridines as Potential Enoyl-Acyl Carrier Protein Reductase Inhibitors: Antitubercular Activity and Molecular Docking Study

2020 ◽  
Vol 20 ◽  
Author(s):  
Katharigatta N. Venugopala ◽  
Christophe Tratrat ◽  
Melendhran Pillay ◽  
Pran Kishore Deb ◽  
Deepak Chopra ◽  
...  
Keyword(s):  
Drug Resistance ◽  
Acyl Carrier Protein ◽  
Phenyl Group ◽  
Antitubercular Activity ◽  
Docking Study ◽  
Benzyl Ester ◽  
Multi Drug Resistance ◽  
Carrier Protein ◽  
Molecular Docking Study ◽  
Lipinski’S Rule

Background: Tuberculosis remains one of the most deadly infectious diseases worldwide due to the emergence of multi-drug resistance (MDR) and extensively drug resistance (XDR) strains of Mycobacterium tuberculosis (MTB). Materials and Methods: Herein, the screening of a total of eight symmetrical 1,4-dihydropyridine (1,4-DHP) derivatives (4a-4h) was carried out for whole-cell anti-TB activity against the susceptible H37Rv and MDR strains of MTB. Results and Discussion: Most of the compounds exhibited moderate to excellent activity against the susceptible H37Rv. Moreover, the most promising compound 4f (against H37Rv) having para-trifluoromethyl phenyl group at 4-position and bis para-methoxy benzyl ester group at 3- and 5-positions of 1,4-dihydropyridine pharmacophore, exhibited no toxicity, but demonstrated weak activity against MTB strains resistant to isoniazid and rifampicin. In light of the inhibitory profile of the title compounds, enoyl-acyl carrier protein reductase (InhA) appeared to be the appropriate molecular target. Docking study of these derivatives against InhA receptor revealed favorable binding interactions. Further, in silico predicted ADME properties of these compounds 4a-4h were found to be in the acceptable ranges including satisfactory Lipinski’s rule of five, thereby indicating their potential as drug-like molecules. Conclusion: In particular, the 1,4-DHP derivative 4f can be considered as an attractive lead molecule for further exploration and development of more potent anti-TB agents as InhA inhibitors.

Infrared spectra and substituent effects in 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones

1983 ◽  
Vol 48 (2) ◽  
pp. 586-595 ◽  
Author(s):  
Alexander Perjéssy ◽  
Pavol Hrnčiar ◽  
Ján Šraga
Keyword(s):  
Substituent Effects ◽  
Phenyl Group ◽  
Wave Number ◽  
Vibrational Coupling ◽  
Wave Numbers ◽  
Stretching Vibration ◽  
Stretching Vibrations ◽  
The Relationship ◽  
Derivatives Of ◽  
Effect Of Structure

The wave numbers of the fundamental C=O and C=C stretching vibrations, as well as that of the first overtone of C=O stretching vibration of 2-(3-, and 4-substituted phenylmethylene)-1,3-cycloheptanediones and 1,3-cycloheptanedione were measured in tetrachloromethane and chloroform. The spectral data were correlated with σ+ constants of substituents attached to phenyl group and with wave number shifts of the C=O stretching vibration of substituted acetophenones. The slope of the linear dependence ν vs ν+ of the C=C stretching vibration of the ethylenic group was found to be more than two times higher than that of the analogous correlation of the C=O stretching vibration. Positive values of anharmonicity for asymmetric C=O stretching vibration can be considered as an evidence of the vibrational coupling in a cyclic 1,3-dicarbonyl system similarly, as with derivatives of 1,3-indanedione. The relationship between the wave numbers of the symmetric and asymmetric C=O stretching vibrations indicates that the effect of structure upon both vibrations is symmetric. The vibrational coupling in 1,3-cycloheptanediones and the application of Seth-Paul-Van-Duyse equation is discussed in relation to analogous results obtained for other cyclic 1,3-dicarbonyl compounds.

1H and 13C NMR spectra of 2,2’-disubstitutedtrans-azobenzenes suitable for preparation of metallized azo dyes

1991 ◽  
Vol 56 (10) ◽  
pp. 2160-2168 ◽  
Author(s):  
Josef Jirman
Keyword(s):  
Nmr Spectra ◽  
Electron Pair ◽  
Phenyl Group ◽  
Aprotic Solvents ◽  
1H And 13C Nmr ◽  
Predominant Form ◽  
Rapid Equilibrium ◽  
Dipolar Aprotic Solvents ◽  
Free Electron Pair ◽  
C Nmr

The 1H and 13C NMR spectra have been measured of six trans-azobenzenes substituted at 2 and 2’ positions with substituents favourable for complex formation with a metal (OH, NH2, NHCOCH3, COOH). From the standpoint of NMR such substituted trans-azobenzenes are present in solution in a rapid equilibrium following from rotation around the bond between C-1 of phenyl group and N atom of azo linkage. The predominant form has the substituent in the syn-position with respect to the free electron pair of the nearer azo nitrogen atom. The equilibrium is affected by dipolar aprotic solvents (such as hexadeuteriodimethyl sulfoxide) by decreasing the presence of the predominant form by 1 to 11%.

Adsorption of Carbon Monoxide on Pd/SiO2/Si(111) Studied by Core-Level Photoemission

1998 ◽  
Vol 63 (11) ◽  
pp. 1793-1802 ◽  
Author(s):  
Zdeněk Bastl ◽  
Tomáš Šarapatka
Keyword(s):  
Carbon Monoxide ◽  
Photoelectron Spectroscopy ◽  
Co Adsorption ◽  
Charge Balance ◽  
Adsorption Activity ◽  
Chemical States ◽  
Adsorbed Co ◽  
Pd Clusters ◽  
Almost All ◽  
P Type

X-Ray photoelectron spectroscopy (XPS) has been used to study the adsorption of carbon monoxide on Pd dispersed on oxidized Si(111) surface. A fraction of the deposited Pd diffusing at room temperature to the SiO2/Si interface increases with decreasing SiO2 thickness. For oxide layers thinner than ≈1 nm, almost all deposited Pd diffuses to SiO2/Si interface forming there Si silicide. Consequently, the amount of adsorbed CO is dependent on the thickness of the thermally grown SiO2 layer. Two different chemical states of adsorbed carbon atoms, the population of which depends on the amount of the Pd deposited, are observed in the C (1s) spectra of adsorbed CO. Adsorption activity of Pd clusters does not depend on whether n- or p-type Si is used. Comparison of the experimental Pd/CO concentration ratios with those calculated assuming several different modes of the Pd growth on SiO2/Si points to the pseudo-Stranski-Krastanow mode (flat clusters with incomplete condensation of the first layer) at 300 K. Changes in charge balance across the Pd/SiO2/Si interface caused by CO adsorption are discussed in terms of the surface photovoltage effect and work function variation.

Investigations of the stability of palladium clusters supported on gold

2005 ◽  
Vol 597 (1-3) ◽  
pp. 127-132 ◽  
Author(s):  
J. Meier ◽  
H. Kleine ◽  
U. Stimming
Keyword(s):  
Palladium Clusters ◽  
The Stability

Synthesis of cobalt A2B triaryl corrole bearing aldehyde and amide pyridyl groups and their performance in electrocatalytic hydrogen evolution

2021 ◽  
Author(s):  
Jun-Jia Fang ◽  
Jian Lan ◽  
Gang Yang ◽  
Gao-Qing Yuan ◽  
Hai-Yang Liu ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Spatial Configuration ◽  
Phenyl Group

Four A2B type cobalt triaryl corrole complexes (1-4) bearing aldehyde and pyridyl substituents at the 10-meso-phenyl group with different spatial configuration had been synthesized and well characterized by HR-MS, NMR,...

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