Simple carbenes as hydrogen bond acceptors: determination of nucleophilicities and reduced nucleophilicities.

Nucleophilicities for a range of simple carbene molecules acting as hydrogen bond acceptors B in forming complexes B⋯HX are reported. The carbenes chosen to fulfil the roles of a Lewis base are B = RM, -(CH)M, HCCM and two N-heterocyclic carbenes, where M is one of the group 14 tetrel atoms, C, Si, Ge or Sn and R = H, CH, and F. All the carbenes but CH have a singlet electronic ground state.

Computational design for enantioselective CO capture: asymmetric frustrated Lewis pairs in epoxide transformations.

Carbon capture and utilisation (CCU) technologies offer a compelling strategy to mitigate rising atmospheric carbon dioxide levels. Despite extensive research on the CO insertion into epoxides to form cyclic carbonates, the stereochemical implications of this reaction have been largely overlooked, despite the prevalence of racemic epoxide solutions. This study introduces an in silico approach to design asymmetric frustrated Lewis pairs (FLPs) aimed at controlling reaction stereochemistry.

Hydride and halide abstraction reactions behind the enhanced basicity of Be and Mg clusters with nitrogen bases.

In this study, we investigate the protonation effects on the structure, relative stability and basicity of complexes formed by the interaction of monomers and dimers of BeX and MgX (X = H, F) with NH, CHNH, HCN, and NCH bases. Calculations were performed using the M06-2X/aug-cc-pVTZ formalism, along with QTAIM, ELF and NCI methods for electron density analysis and MBIE and LMO-EDA energy decomposition analyses for interaction enthalpies. The protonation of the MH- and MH-Base complexes occurs at the negatively charged hydrogen atoms of the MH and MH moieties through typical hydride abstraction reactions, while protonation at the N atom of the base is systematically less exothermic.

Investigation of Tetrel Bonds in Isolated Complexes Formed Between a Lewis Acid HMX, M-O or M-S (M = Si, Ge, or Sn) and the Lewis Bases B = N, CO, HCCH, PH, CH, HCN, CS, HNC, NP, HO, and NH.

Isolated complexes of the type B⋯A in which the noncovalent interaction is a tetrel bond have been characterized by calculations at the CCSD(T)(F12c)/cc-pVDZ-F12 level. The Lewis bases B involved were N, CO, HCCH, PH, CH, HCN, CS, HNC, NP, HO and NH. Two types of Lewis acid A were examined, each containing one of the tetrel atoms M = Si, Ge or Sn, The Lewis acids in the first series were the HMX (X = F, Cl, CN, H), in each of which the most electrophilic region was found to lie on the axis of the C molecules, near to the tetrel atom M.

Beryllium as a Base: Complexes of Be(CO) with HX (X=F, Cl, Br, CN, NC, CCH, OH).

Beryllium chemistry is typically governed by its electron deficient character, but in some compounds it can act as a base. In order to understand better the unusual basicity of Be, we have systematically explored the complexes of one such compound, Be(CO), towards several hydrogen bond donors HX (X=F, Cl, Br, CN, NC, CCH, OH). For all complexes we find three different minima, two hydrogen bonded minima (to the Be or O atoms), and one weak beryllium bonded minimum.

Understanding the coupling of non-metallic heteroatoms to CO from a Conceptual DFT perspective.

Context: A Conceptual DFT (CDFT) study has been carry out to analyse the coupling reactions of the simplest amine (CHNH), alcohol (CHOH), and thiol (CHSH) compounds with CO to form the corresponding adducts CHNHCOH, CHOCOH, and CHSCOH. The reaction mechanism takes place in a single step comprising two chemical events: nucleophilic attack of the non-metallic heteroatoms to CO followed by hydrogen atom transfer (HAT). According to our calculations, the participation of an additional nucleophilic molecule as HAT assistant entails important decreases in activation electronic energies.

Monohydrides of the Group 13 Elements M=B, Al and Ga: Axial Bi-Nucleophilicity and the Propensity to Form Both H-M⋅⋅⋅HX and M-H⋅⋅⋅HX Hydrogen Bonds (X=F, Cl, Br, I, CN, CCH, CP).

Equilibrium dissociation energies D of the hydrogen-bonded complexes HAl⋅⋅⋅HX and HGa⋅⋅⋅HX (X=F, Cl, Br, I, CN, CCH, and CP) were calculated ab initio at the CCSD(T)-(F12c)/cc-pVDZ-F12 level of theory. The gradients of graphs of D versus the electrophilicity E of the Lewis acids HX yielded the nucleophilicities N of the Group 13 atoms M in these diatomic molecules. Molecular electrostatic surfaces potentials reveal that H-Al and H-Ga are bi-nucleophilic and that the H ends of these H-M molecules are more nucleophilic than the M ends for M=Al and Ga, but not when M=boron.

Expanding the focus of the One Health concept: links between the Earth-system processes of the planetary boundaries framework and antibiotic resistance.

The scientific community warns that our impact on planet Earth is so acute that we are crossing several of the planetary boundaries that demarcate the safe operating space for humankind. Besides, there is mounting evidence of serious effects on people's health derived from the ongoing environmental degradation. Regarding human health, the spread of antibiotic resistant bacteria is one of the most critical public health issues worldwide.

Striking Borane Planarization in the Thermal Rearrangement (η-CH)Fe(η-BH)→(η-CH)Fe(η-BH).

In 1977 Weiss and Grimes, by means of mass spectrometry and H and B NMR spectroscopy, proposed two structures (I and II) for the ferraborane (η-CH)Fe(BH), isoelectronic with ferrocene. In this work, by means of high-level quantum-chemical computations, we confirm the experimental structures of the two isomers with their corresponding energies, and assign the reported H and B NMR chemical shifts. A striking result from this study is the planarization (3D→2D) of the BH ligand - an unknown isolated anion, isoelectronic with aromatic cyclopentadienyl anion CH - when attached to the (η-CH)Fe moiety, thus resulting in a more stable ferraborane isomer II.

Hydrogen Bonds Are Never of an "Anti-electrostatic" Nature: A Brief Tour of a Misleading Nomenclature.

A large amount of scientific works have contributed through the years to rigorously reflect the different forces leading to the formation of hydrogen bonds, the electrostatic and polarization ones being the most important among them. However, we have witnessed lately with the emergence of a new terminology, anti-electrostatic hydrogen bonds (AEHBs), that seems to contradict this reality. This nomenclature is used in the literature to describe hydrogen bonds between equally charged systems to justify the existence of these species, despite numerous proofs showing that AEHBs are, as any other hydrogen bond between neutral species, mostly due to electrostatic forces.

A multi-FLP approach for CO capture: investigating nitrogen, boron, phosphorus and aluminium doped nanographenes and the influence of a sodium cation.

The reactivity of BN-doped hexa-cata-hexabenzocoronene (BN-NG), AlN-NG, BP-NG and AlP-NG, models of doped nanographenes (NGs), towards carbon dioxide was studied with density functional theory (DFT) calculations at the M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G* level of theory. The NG systems exhibit a poly-cyclic poly-frustrated Lewis pair (FLP) nature, featuring multiple Lewis acid/Lewis base pairs on their surface enabling the capture of several CO molecules. The capture of CO by these systems was investigated within two scenarios: (A) sequential capture of up to three CO molecules and (B) capture of CO molecules in the presence of a sodium cation.

Discovering trends in the Lewis acidity of beryllium and magnesium hydrides and fluorides with increasing clusters size.

We have reported in the last years the strong effect that Be- and Mg-containing Lewis acids have on the intrinsic properties of typical bases, which become acids upon complexation. In an effort to investigate these changes when the Be and Mg derivatives form clusters of increasing size, we have examined the behavior of the (MX) (M = Be, Mg; X = H, F; n = 1, 2, 3) clusters when they interact with ammonia, methanimine, hydrogen cyanide and pyridine, and with their corresponding deprotonated forms. The complexes obtained at the M06-2X/aug-cc-pVTZ level were analyzed using the MBIE energy decomposition formalism, in parallel with QTAIM, ELF, NCIPLOT and AdNDP analyses of their electron density.

Capture of CO by Melamine Derivatives: A DFT Study Combining the Relative Energy Gradient Method with an Interaction Energy Partitioning Scheme.

A theoretical study of the interaction between melamine and CO was carried out using density functional theory (DFT) with the B3LYP-D3(BJ)/aug-cc-pVTZ level of theory. The presence of anions interacting with melamine transforms the weakly bonded tetrel complexes into adducts. Thus, melamine acts as an FLP (frustrated Lewis pair) with acid groups (NHs as hydrogen bond donors) and a base group (N of the triazine ring).

Towards 2D Borane Chemistry in Hexagonal Cyclic Compounds.

A comprehensive comparison between known benzene mono-substituted compounds R-Ph and the corresponding isoelectronic unknown R-cyclohexaborane(12) molecules is carried out from a geometric and electronic structure point of view, with R={H, BH, CH, NH, OH, F ; AlH, SiH, PH, SH, Cl ; NO, OCH}. We suggest new chemical names for the 2D borane compounds and analyze the geometric and electronic structure carbon vs. boron comparatives by means of HOMO-LUMO gaps, bonding schemes, electron density topological properties and predicted NMR chemical shifts.

An ab Initio Study of High-Energetic Trioxatriazinane Derivatives: Conformational Analysis, Nitrogen Inversion, Heats of Formation, Dissociation Reaction, and Dimerization.

High-energetic materials belong to two main classes: propellants and explosives. The still rather unexplored family of 1,3,5,2,4,6-trioxatriazinanes, NOR, has a representative of each class. We have selected three compounds, R = H, R = CH and R = NO, this last compound being known as TNTOTA, "trinitro-trioxa-triazinane".

Plasmid content of carbapenem resistant isolates belonging to five International Clones collected from hospitals of Alexandria, Egypt.

Multidrug resistant is one of the most important nosocomial pathogens worldwide. During the last decades it has become a major threat for healthcare settings due to the high antibiotic resistance rates among these isolates. Many resistance determinants are coded by conjugative or mobilizable plasmids, facilitating their dissemination.

(Pyridin-2-ylmethyl)triel Derivatives as Masked Frustrated Lewis Pairs. Interactions and CO -Sequestration.

The isolated (pyridin-2-ylmethyl)triel derivatives (triel=B, Al and Ga) show an intramolecular N⋅⋅⋅Tr triel bond as shown by compounds found in the Cambridge Structural Database and DFT calculations. The possibility to use them as masked frustrated Lewis pairs (mFLP) has been explored theoretically concerning their reaction with CO . The adduct formation proceeds in two steps.

A Holistic View of the Interactions between Electron-Deficient Systems: Clustering of Beryllium and Magnesium Hydrides and Halides.

In the search for common bonding patterns in pure and mixed clusters of beryllium and magnesium derivatives, the most stable dimers and trimers involving BeX and MgX (X = H, F, Cl) have been studied in the gas phase using B3LYP and M06-2X DFT methods and the G4 ab initio composite procedure. To obtain some insight into their structure, stability, and bonding characteristics, we have used two different energy decomposition formalisms, namely MBIE and LMO-EDA, in parallel with the analysis of the electron density with the help of QTAIM, ELF, NCIPLOT, and AdNDP approaches. Some interesting differences are already observed in the dimers, where the stability sequence observed for the hydrides differs entirely from that of the fluorides and chlorides.

A case for the importance of following antibiotic resistant bacteria throughout the soil food web.

It is necessary to complement next-generation sequencing data on the soil resistome with theoretical knowledge provided by ecological studies regarding the spread of antibiotic resistant bacteria (ARB) in the abiotic and, especially, biotic fraction of the soil ecosystem. Particularly, when ARB enter agricultural soils as a consequence of the application of animal manure as fertilizer, from a microbial ecology perspective, it is important to know their fate along the soil food web, that is, throughout that complex network of feeding interactions among members of the soil biota that has crucial effects on species richness and ecosystem productivity and stability. It is critical to study how the ARB that enter the soil through the application of manure can reach other taxonomical groups (e.

Development of a high-throughput platform to measure plasmid transfer frequency.

Antibiotic resistance represents one of the greatest threats to global health. The spread of antibiotic resistance genes among bacteria occurs mostly through horizontal gene transfer via conjugation mediated by plasmids. This process implies a direct contact between a donor and a recipient bacterium which acquires the antibiotic resistance genes encoded by the plasmid and, concomitantly, the capacity to transfer the acquired plasmid to a new recipient.

Metastable Charged Dimers in Organometallic Species: A Look into Hydrogen Bonding between Metallocene Derivatives.

Multiply charged complexes bound by noncovalent interactions have been previously described in the literature, although they were mostly focused on organic and main group inorganic systems. In this work, we show that similar complexes can also be found for organometallic systems containing transition metals and deepen in the reasons behind the existence of these species. We have studied the structures, binding energies, and dissociation profiles in the gas phase of a series of charged hydrogen-bonded dimers of metallocene (Ru, Co, Rh, and Mn) derivatives isoelectronic with the ferrocene dimer.

A theoretical study of the reaction of borata derivatives of benzene, anthracene and pentacene with CO.

A theoretical study of the reaction between several borataacenes (1-methylboratabenzene, 9-methyl-9-borataanthracene and and diboratapentacene) and CO has been carried out at the M06-2X computational level. The influence of a counterion (potassium cation), the cation complexation by 18-crown-6-ether and solvent effects have been explored. The computational results predict / selectivity as found experimentally in the - and -diboratapentacene reaction with CO (Baker , , 2023, , 2028).

Co-Existence of , , , and in a Clinical Isolate of from Alexandria, Egypt.

The increasing rates of antimicrobial resistance among carbapenem-resistant in the Middle East and North Africa are one of the major concerns for healthcare settings. We characterised the first isolate harbouring five β-lactamases identified in Egypt. The isolate Ale25 was obtained from an ICU patient of a hospital from Alexandria.

Molecular characterization of multidrug resistant clinical isolates from Alexandria, Egypt.

Carbapenem resistant is a major global concern, especially in countries of the Middle East and North Africa, where the antibiotic resistance rates are on the rise. The aim of this study was to study the genomic characteristics and antimicrobial susceptibility profile of thirty-six multidrug resistant clinical isolates obtained in hospitals from Alexandria, Egypt. Antibiotic resistance rates were estimated by determination of Minimum Inhibitory Concentrations.