Számításos kémiai módszerekkel támogatott foszfor- és szilíciumkémia = Computationally assisted of organophosphorus and organosilicon chemistry

A kutatás során a 14-es (C, Si, Ge, Sn) illetve a 15-ös (N,P) főcsoport elemeit tartalmazó molekulák vizsgálatával foglalkoztunk. Eredményeinket részben különleges kötésszerkezetek (karbének, foszfinidének) illetve hipervalens vegyületek előállíthatósága és stabilizációjuk lehetséges módjainak vizsgálatában értük el. Külön kiemelendő a konjugált foszfortartalmú rendszerek vizsgálata, melyeket szintetikus kutatócsoportokkal együttműködve végeztünk. Optoelektronikai alkalmazásokra felhasználható különböző konjugált/kondenzált foszfolszármazékok vizsgálatával Regis Reau és Thomas Baumgartner csoportjaival együttműködve születtek eredmények, míg a kationos, semleges és anionos diazafoszfol alapvázat Dietrich Gudat csoportjával együttműködve vizsgáltuk. Proazafoszfatrán szuperbázis és származékainak (John Verkade-val együttműködve) vizsgálata stabilizációjában megállapítottuk a transzannulláció szerepét és mértékét. Vizsgáltuk sziloxánláncok kialakulásának mechanizmusát és e láncok stabilitását. | The target molecules of our research contain group 14 (C, Si, Ge, Sn) and group 15 (N,P) elements. The most important results are related to unusual bonded molecules including carbenes, phosphinidenes, and hypervalent molecules, including their stabilization and synthesizability. Especially noteworthy results were obtained in cooperation with synthetic research groups in the field of conjugated organophosphorus compounds. Different cunjugated/annellated phosphole-based ring systems were targeted in cooperations with Regis Reau and Thomas Baumgartner. Cationic, neutral and anionic diazaphosphole systems were investigated with the Group of Dietrich Gudat. Investigating the proazaphosphatrane superbase and its derivatives (in a joint work with John Verkade) we have established the effect and extent of transannullation. The formation and the stability of siloxane chains was also investigated

On the rich chemistry of pseudo‐protic ionic liquid electrolytes

Mixing weak acids and bases can produce highly complicated binary mixtures, called pseudo-protic ionic liquids, in which a complex network of effects determines the physicochemical properties that are currently impossible to predict. In this joint computational-experimental study, we investigated 1-methylimidazole-acetic acid mixtures through the whole concentration range. Effects of the varying ionization and excess of either components on the properties, such as density, diffusion coefficients, and overall hydrogen bonding structure were uncovered. A special emphasis was put on understanding the multiple factors that govern the conductivity of the system. In the presence of an excess of acetic acid, the 1-methylimidazolium acetate ion pairs dissociate more efficiently, resulting in a higher concentration of independently moving, conducting ions. However, the conductivity measurements showed that higher concentrations of acetic acid improve the conductivity beyond this effect, suggesting in addition to standard dilution effects the occurrence of Grotthuss diffusion in high acid-to-base ratios. The results here will potentially help designing novel electrolytes and proton conducting systems, which can be exploited in a variety of applications

Liquid Dynamics Determine Transition Metal-N-Heterocyclic Carbene Complex Formation

The mechanism of metal-N-heterocyclic carbene (NHC) complex formation from imidazolium salts in the presence of weak bases was investigated through theoretical methods. Quantum chemical calculations revealed that the two bases considered here, sodium acetate and trimethylamine, both facilitate complex formation. In contrast to previous experiments, these calculations indicated a slightly lower barrier with the amine. Molecular dynamics simulations showed that the ionic nature of the [AuCl2]− and imidazolium ions, as well as the sodium acetate base keep these species associated in the reaction mixture through ion pairing. This pre-association of the components produces those clusters that are essential for the metal complex formation reaction. The neutral amine, however, remains mostly separated from the other reaction partners, making it a significantly less effective base

Synergistic Catalysis in Heterobimetallic Complexes for Homogeneous Carbon Dioxide Hydrogenation

Two heterobimetallic Mo,M’ complexes (M’ = IrIII, RhIII) were synthesized and fully characterized. Their catalytic activity in homogeneous carbon dioxide hydrogenation to formate was studied. A pronounced synergistic effect between the two metals was found, most notably between Mo and Ir, leading to a fourfold increase in activity compared with a binary mixture of the two monometallic counterparts. This synergism can be attributed to spatial proximity of the two metals rather than electronic interactions. To further understand the nature of this interaction, the mechanism of the CO2 hydrogenation to formate by a monometallic IrIII catalyst was studied using computational and spectroscopic methods. The resting state of the reaction was found to be the metal-base adduct, whereas the rate-determining step is the inner-sphere hydride transfer to CO2. Based on these findings, the synergism in the heterobimetallic complex is beneficial in this key step, most likely by further activating the CO2

Micro- and Nanoplastics Breach the Blood–Brain Barrier (BBB): Biomolecular Corona’s Role Revealed

Humans are continuously exposed to polymeric materials such as in textiles, car tires and packaging. Unfortunately, their break down products pollute our environment, leading to widespread contamination with micro- and nanoplastics (MNPs). The blood–brain barrier (BBB) is an important biological barrier that protects the brain from harmful substances. In our study we performed short term uptake studies in mice with orally administered polystyrene micro-/nanoparticles (9.55 µm, 1.14 µm, 0.293 µm). We show that nanometer sized particles—but not bigger particles—reach the brain within only 2 h after gavage. To understand the transport mechanism, we performed coarse-grained molecular dynamics simulations on the interaction of DOPC bilayers with a polystyrene nanoparticle in the presence and absence of various coronae. We found that the composition of the biomolecular corona surrounding the plastic particles was critical for passage through the BBB. Cholesterol molecules enhanced the uptake of these contaminants into the membrane of the BBB, whereas the protein model inhibited it. These opposing effects could explain the passive transport of the particles into the brain

A New Oxygen Containing Pyclen-Type Ligand as a Manganese(II) Binder for MRI and 52Mn PET Applications: Equilibrium, Kinetic, Relaxometric, Structural and Radiochemical Studies

A new pyclen-3,9-diacetate derivative ligand (H23,9-OPC2A) is synthesized possessing an etheric O-atom opposite to the pyridine ring to improve the dissociation kinetics of its Mn(II) complex (pyclen = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene). The new ligand is less basic than the N-containing analogue (H23,9-PC2A) due to the non-protonable O-atom. In spite of its lower basicity, the conditional stability of the [Mn(3,9-OPC2A)] (pMn=-log[Mn(II)], cL=cMn(II)=0.01 mM. pH=7.4) remains unaffected (pMn=8.69) compared to the [Mn(3,9-PC2A)] (pMn=8.64). The [Mn(3,9-OPC2A)] possesses one water molecule, having a lower exchange rate with bulk solvent (kex298=5.30.4107 s-1) than [Mn(3,9-PC2A)] (kex298=1.26108 s-1). These mild differences are ration-alized by density-functional theory (DFT) calculations. The acid assisted dissociation of [Mn(3,9-OPC2A)] is considerably slower (k1=2.810.07 M-1s-1) than that of the complexes of diac-etates or bisamides of various 12-membered macrocycles and the parent H23,9-PC2A. The [Mn(3,9-OPC2A)] is inert in rat/human serum as confirmed by 52Mn labeling (nM range) as well as by relaxometry (mM range). However, 600-fold excess of EDTA (pH=7.4) or a mixture of es-sential metal ions propagated some transchelation/transmetalation in 7 days. The H23,9-OPC2A is labeled efficiently with 52Mn at elevated temperatures, yet at 37 oC the parent H23,9-PC2A per-forms slightly better. Altogether the H23,9-OPC2A shows advantageous features for further lig-and design for bifunctional chelators

Mapping the Free Energy of Lithium Solvation in the Protic Ionic Liquid Ethylammonuim Nitrate: A Metadynamics Study

Understanding lithium solvation and transport in ionic liquids is important due to their possible application in electrochemical devices. Using first-principles simulations aided by a metadynamics approach we study the free-energy landscape for lithium ions at infinite dilution in ethylammonium nitrate, a protic ionic liquid. We analyze the local structure of the liquid around the lithium cation and obtain a quantitative picture in agreement with experimental findings. Our simulations show that the lowest two free energy minima correspond to conformations with the lithium ion being solvated either by three or four nitrate ions with a transition barrier between them of 0.2 \eV. Other less probable conformations having different solvation pattern are also investigated