INFLUENCE OF HALOGEN NATURE ON THE ADSORPTION ABILITY OF ARYL HALIDES ON PALLADIUM 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.

Magnetic moment quenching in small Pd clusters in solution

Small palladium clusters in vacuum show pronounced magnetic moments. With the help of Born–Oppenheimer molecular dynamics simulations based on density functional theory, we investigate for the paradigmatic examples of the Pd$$_{13}$$ 13 and the Pd$$_8$$ 8 cluster whether these magnetic moments prevail when the clusters are solvated. Our results show that the interaction with acetophenone quenches the magnetic moment. The reduction of the magnetic moment is a direct consequence of the electronic interaction between the Pd clusters and the solvent molecules, and not an indirect effect due to a different cluster geometry being stabilized by the solvation shell. Graphical Abstract

NHC Polymeric Particles Obtained by Self-Assembly and Click Approach of Calix[4]Arene Amphiphiles as Support for Catalytically Active Pd Nanoclusters

A new polymeric NHC carrier was synthesized by sequential supramolecular self-assembly and copper-catalyzed azide-alkyne cycloaddition (CuAAC) of amphiphilic imidazolium calix[4]arenes with octyl lipophilic fragments. Obtained polytriazole-imidazolium particles were found as monodisperse submicron particles, with the average diameter of 236 ± 34 nm and average molecular weight of 1380 ± 96 kDa. Successful CuAAC polymerization has been proved using IR spectroscopy and high-resolution ESI mass spectrometry. Polymeric particles, as well as aggregates made from precursor macrocycles, were decorated by Pd clusters (2 nm) for further catalytic investigations. Pd nanoclusters, supported on the polymeric surface, were found highly catalytically active in the model reduction of p-nitrophenol, giving reaction rates an order of magnitude higher compared to literature examples. The reaction was recycled using the same catalyst five times without any loss of activity.

Tuning the selectivity of catalytic nitriles hydrogenation by structure regulation in atomically dispersed Pd catalysts

The product selectivity in catalytic hydrogenation of nitriles is strongly correlated with the structure of the catalyst. In this work, two types of atomically dispersed Pd species stabilized on the defect-rich nanodiamond-graphene (ND@G) hybrid support: single Pd atoms (Pd1/ND@G) and fully exposed Pd clusters with average three Pd atoms (Pdn/ND@G), were fabricated. The two catalysts show distinct difference in the catalytic transfer hydrogenation of nitriles. The Pd1/ND@G catalyst preferentially generates secondary amines (Turnover frequency (TOF@333 K 709 h−1, selectivity >98%), while the Pdn/ND@G catalyst exhibits high selectivity towards primary amines (TOF@313 K 543 h−1, selectivity >98%) under mild reaction conditions. Detailed characterizations and density functional theory (DFT) calculations show that the structure of atomically dispersed Pd catalysts governs the dissociative adsorption pattern of H2 and also the hydrogenation pathway of the benzylideneimine (BI) intermediate, resulting in different product selectivity over Pd1/ND@G and Pdn/ND@G, respectively. The structure-performance relationship established over atomically dispersed Pd catalysts provides valuable insights for designing catalysts with tunable selectivity.

STRUCTURAL-PHASE TRANSFORMATIONS IN FILMS AT THE INTERFACE OF THE HETEROSYSTEM “GLASS - CLUSTERS Ag-Pd” – Sn-Pb

Structural-phase transformations in films at the interface of the heterosystem "glass - Ag-Pd clusters" – Sn-Pb have been investigated. The relationship between these transformations and the initial system material component dispersion is established at the same film element temperature operating mode. It is shown that structural-phase transformations in contact elements of hybrid integrated circuits microelectronic devices, sensors and solar cells, etc. made of functional materials based on the specified heterosystem can lead to degradation processes and, as a consequence, to a decrease in the electronic product reliability.

Understanding perceived social support among women with personality disorder clusters

Objective: This study aimed to understand perceived social support (PSS) among women with personality disorder (PD). We also investigated potential differences in PSS according to PD clusters (clusters A, B, C). Methods: Women ( n = 718) from the Geelong Osteoporosis Study completed the Multidimensional Scale of Perceived Social Support (MPSS) and Structured Clinical Interview for DSM-IV Axis II Disorders. Multivariable regression and analyses of covariance were employed, controlling for psychiatric and sociodemographic confounders. Results: After age-adjustment, PD (any) and the PD clusters were negatively associated with PSS across all subscales. Bonferroni-adjusted pairwise comparisons revealed lower: significant other PSS for cluster A; family PSS for cluster C, friend PSS for clusters B and C; and total PSS for clusters B and C. Conclusion: Aspects of PSS were predominantly lower among women with cluster B and C PDs.

Element-specific contributions to improved magnetic heating of theranostic CoFe2O4 nanoparticles decorated with Pd

Decoration with Pd clusters increases the magnetic heating ability of cobalt ferrite (CFO) nanoparticles by a factor of two. The origin of this previous finding is unraveled by element-specific X-ray absorption spectroscopy (XAS) and magnetic circular dichroism (XMCD) combined with atomic multiplet simulations and density functional theory (DFT) calculations. While the comparison of XAS spectra with atomic multiplet simulations show that the inversion degree is not affected by Pd decoration and, thus, can be excluded as a reason for the improved heating performance, XMCD reveals two interrelated responsible sources: significantly larger Fe and Co magnetic moments verify an increased total magnetization which enhances the magnetic heating ability. This is accompanied by a remarkable change in the field-dependent magnetization particularly for Co ions which exhibit an increased low-field susceptibility and a reduced spin canting behavior in higher magnetic fields. Using DFT calculations, these findings are explained by reduced superexchange between ions on octahedral lattice sites via oxygen in close vicinity of Pd, which reinforces the dominating antiparallel superexchange interaction between ions on octahedral and tetrahedral lattice sites and thus reduces spin canting. The influence of the delocalized nature of Pd 4d electrons on the neighboring ions is discussed and the conclusions are illustrated with spin density isosurfaces of the involved ions. The presented results pave the way to design nanohybrids with tailored electronic structure and magnetic properties.