Transmetalation of Boronic Acids and their Derivatives: Mechanistic Elucidation and Relevance to Catalysis

The Suzuki–Miyaura reaction (cross-coupling reaction of boronic acids with organic halides catalysed by Pd complexes) has been recognised as the useful synthetic organic reaction that forms a C(sp2)–C(sp2) bond. The...

Study of the correlation between the clinical manifestations of the inflammatory periodontal diseases and the microbiome of periodontal pathogenic microflora in young representatives of a mixed population of the European region

The age of inflammatory periodontal disease (PD) manifestations has tended to decrease over the past decades. The study of the range of periodontal pathogens in young people and their influence on the PD manifestation contributes to the predictor identification for the early prevention of this pathology.The aim was to study the correlation between the range of periodontal pathogens in the dentoalveolar sulcus/periodontal pocket (DS/PC) contents and the clinical PD manifestations in young people.We examined 28 patients (23.1 ± 0.93 years) with dental biofilm-induced gingivitis (BG), 24 patients (30.7 ± 0.6 years) with aggressive periodontitis (AgP), and 87 clinically periodontally healthy patients (21.1 ± 0.49 years) (Control). The hygiene index and the periodontal status were determined in all patients. DNA of five periodontal pathogens was identified by PCR in the DS/PC contents. The statistical analysis was performed in Statistica 13.3. The critical significance level was p ≤ 0.05.DNA was not observed in 60.9 % of the control group samples and 7.1 % of the BG group samples. In other cases, the bacteria were found separately and as part of bacterial complexes. P.g. and T.f. were most often detected in all groups. P.g. (U = 474, р < 0.01) and A.a. (U = 209, р >< 0.05) significantly contributed to the plaque formation in the control group, T.d. – in BG and AgP groups (U = 37.5, р >< 0.05 and U = 34, р >< 0.05, respectively). In the AgP group, purulent discharge was more often recorded if T.d. was detected in the PC contents (χ2 = 5.53, р >< 0.05). T.f. + P.i. and P.g. + T.f. + P.i. complexes were exclusively associated with PD. Complexes of four bacteria were found only in the AgP group. The association of periodontal pathogens and their complexes with different PD forms was revealed.>< 0.01) and A.a. (U = 209, р <0.05) significantly contributed to the plaque formation in the control group, T.d. – in BG and AgP groups (U = 37.5, р <0.05 and U = 34, р <0.05, respectively). In the AgP group, purulent discharge was more often recorded if T.d. was detected in the PC contents (χ2 = 5.53, р <0.05). T.f. + P.i. and P.g. + T.f. + P.i. complexes were exclusively associated with PD. Complexes of four bacteria were found only in the AgP group.The association of periodontal pathogens and their complexes with different PD forms was revealed.

On the Oxygen Reduction Reaction Mechanism Catalyzed by Pd Complexes on 2D Carbon. A Theoretical Study

Oxygen Reduction Reaction (ORR) is the bottle-neck strategic reaction ruling the fuel cell efficiency process. The slow kinetics of the reaction require highly effective electrocatalysts for proper boosting. In this field, composite catalysts formed by carbon nanotubes functionalized with palladium(II) complexes showed surprising catalytic activity comparable to those of a commercial Pt electrode, but the catalytic mechanisms of these materials still remain open to discussion. In this paper, we propose the combination of experimental and theoretical results to unfold the elementary reaction steps underlying the ORR catalysis.

Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination During Au- and Pd-Catalyzed Diol Cyclization

Au and Pd complexes have emerged as highly effective π-bond cyclization catalysts to construct heterocycles. These cyclization reactions are generally proposed to proceed through multi-step addition-elimination mechanisms involving Au- or Pd-alkyl intermediates. For Au- and Pd-catalyzed allylic diol cyclization, while the DFT potential energy surface landscapes show a stepwise sequence of alkoxylation π-addition, proton transfer, and water elimination, quasiclassical direct dynamics simulations reveal new dynamical mechanisms that depend on the metal center. For Au, trajectories reveal that after π-addition the Au-alkyl intermediate is always skipped because addition is dynamically coupled with proton transfer and water elimination. In contrast, for Pd catalysis, due to differences in the potential-energy landscape shape, only about half of trajectories show Pd-alkyl intermediate skipping. The other half of the trajectories show the traditional two-step mechanism with the intervening Pd-alkyl intermediate. Overall, this work reveals that interpretation of a DFT potential-energy landscape can be insufficient to understand catalytic intermediates and mechanisms and that atomic momenta through dynamics simulations is needed to determine if an intermediate is genuinely part of a catalytic cycle.<br>

Catalysis with a Skip: Dynamically Coupled Addition, Proton Transfer, and Elimination During Au- and Pd-Catalyzed Diol Cyclization

Au and Pd complexes have emerged as highly effective π-bond cyclization catalysts to construct heterocycles. These cyclization reactions are generally proposed to proceed through multi-step addition-elimination mechanisms involving Au- or Pd-alkyl intermediates. For Au- and Pd-catalyzed allylic diol cyclization, while the DFT potential energy surface landscapes show a stepwise sequence of alkoxylation π-addition, proton transfer, and water elimination, quasiclassical direct dynamics simulations reveal new dynamical mechanisms that depend on the metal center. For Au, trajectories reveal that after π-addition the Au-alkyl intermediate is always skipped because addition is dynamically coupled with proton transfer and water elimination. In contrast, for Pd catalysis, due to differences in the potential-energy landscape shape, only about half of trajectories show Pd-alkyl intermediate skipping. The other half of the trajectories show the traditional two-step mechanism with the intervening Pd-alkyl intermediate. Overall, this work reveals that interpretation of a DFT potential-energy landscape can be insufficient to understand catalytic intermediates and mechanisms and that atomic momenta through dynamics simulations is needed to determine if an intermediate is genuinely part of a catalytic cycle.<br>