Following the Molecular Mechanism for the NH3 + LiH → LiNH2 + H2 Chemical Reaction: A Study Based on the Joint Use of the Quantum Theory of Atoms in Molecules (QTAIM) and Noncovalent Interaction (NCI) Index

Structural, computational and in silico studies of 4-bromo-3-flurobenzonitrile as anti-Alzheimer and anti-Parkinson agents

A novel dimer of the 4-bromo-3-fluorobenzonitrile was crystallized and studied using a spectroscopic method such as the scanning electron microscope method. The computational simulations substantiated the structural analysis findings. The Hirshfeld surface analysis has been performed for visualizing, exploring and quantifying the intra and inter-molecular interactions that stabilize the crystal packing of the compound. The NBO and QTAIM analyses were applied to study the nature and origin of the attractive forces involved in the crystal structure. Further, the pharmacokinetic properties of the compound were evaluated, indicating good brain-blood barrier and central nervous system penetration capability. Hence, in silico studies was carried out to explore the binding pattern of the titled compound against acetylcholinesterase and butyrylcholinesterase, and tumor necrosis factor-alpha converting enzyme proteins using molecular docking and molecular dynamics simulations approach. Further, the titled compound is compared with standard drugs through molecular docking studies. The in silico studies finally predicts that the compound under investigation may act as a good inhibitor for treating Alzheimer's disease and further in vitro and in vivo studies may provide its therapeutic potential.Communicated by Ramaswamy H. Sarma.

Mechanistic Study on Artificial Stabilization of Lithium Metal Anode via Thermal Pyrolysis of Ammonium Fluoride in Lithium Metal Batteries

The use of the "Holy Grail" lithium metal anode is pivotal to achieve superior energy density. However, the practice of a lithium metal anode faces practical challenges due to the thermodynamic instability of lithium metal and dendrite growth. Herein, an artificial stabilization of lithium metal was carried out via the thermal pyrolysis of the NH4F salt, which generates HF(g) and NH3(g). An exposure of lithium metal to the generated gas induces a spontaneous reaction that forms multiple solid electrolyte interface (SEI) components, such as LiF, Li3N, Li2NH, LiNH2, and LiH, from a single salt. The artificially multilayered protection on lithium metal (AF-Li) sustains stable lithium stripping/plating. It suppresses the Li dendrite under the Li||Li symmetric cell. The half-cell Li||Cu and Li||MCMB systems depicted the attributions of the protective layer. We demonstrate that the desirable protective layer in AF-Li exhibited remarkable capacity retention (CR) results. LiFePO4 (LFP) showed a CR of 90.6% at 0.5 mA cm-2 after 280 cycles, and LiNi0.5Mn0.3Co0.2O2 (NCM523) showed 58.7% at 3 mA cm-2 after 410 cycles. Formulating the multilayered protection, with the simultaneous formation of multiple SEI components in a facile and cost-effective approach from NH4F as a single salt, made the system competent.

The iron group transition-metal (Fe, Ru, Os) coordination of Se-doped graphitic carbon (Se@g-C3N4) nanostructures for the smart therapeutic delivery of zidovudine (ZVD) as an antiretroviral drug: a theoretical calculation perspective

This study employed density functional theory (DFT) computational techniques at the ωB97XD/def2svp level of theory to comprehensively explore the electronic behavior of Fe-group transition metal (Fe, Ru, Os) coordination of Se-doped graphitic carbon (Se@g-C3N4) nanosystems in the smart delivery of zidovudine (ZVD), an antiretroviral drug. The HOMO-LUMO results of the interactions show a general reduction in energy gap values across all complexes in the following order: ZVD_Se@C3N4 < ZVD_Ru_Se@C3N4 < ZVD_Fe_Se@C3N4 < ZVD_Os_Se@C3N4. ZVD_Se@C3N4 exhibits the smallest post-interaction band gap of 3.783 eV, while ZVD_Os_Se@C3N4 presents the highest energy band gap of 5.438 eV. Results from the corrected adsorption energy (BSSE) revealed that Os_Se@C3N4 and Ru_Se@C3N4 demonstrated more negative adsorption energies of -2.67 and -2.701 eV, respectively, pointing to a more favorable interaction between ZVD and these systems, thus potentially enhancing the drug delivery efficiency. The investigation into the drug release mechanism from the adsorbents involved a comprehensive examination of the dipole moment and the influence of pH, shedding light on the controlled release of ZVD. Additionally, investigating the energy decomposition analysis (EDA) revealed that ZVD_Ru_Se@C3N4 and ZVD_Fe_Se@C3N4 exhibited the same total energy of -787.7 kJ mol-1. This intriguing similarity in their total energy levels suggested that their stability was governed by factors beyond reactivity, possibly due to intricate orbital interactions. Furthermore, analyzing the bond dissociation energies showed that all systems exhibited negative enthalpy values, indicating that these systems were exothermic at both surface and interaction levels, thus suggesting that these processes emitted heat, contributing to the surrounding thermal energy.

Exploring the Mechanism of the Intramolecular Diels-Alder Reaction of (2E,4Z,6Z)-2(allyloxy)cycloocta-2,4,6-trien-1-one Using Bonding Evolution Theory

In the present work, the bond breaking/forming events along the intramolecular Diels-Alder (IMDA) reaction of (2E,4Z,6Z)-2(allyloxy)cycloocta-2,4,6-trien-1-one have been revealed within bonding evolution theory (BET) at the density functional theory level, using the M05-2X functional with the cc-pVTZ basis set. Prior to achieving this task, the energy profiles and stationary points at the potential energy surface (PES) have been characterized. The analysis of the results finds that this rearrangement can proceed along three alternative reaction pathways (a-c). Paths a and b involve two steps, while path c is a one-step process. The first step in path b is kinetically favored, and leads to the formation of an intermediate step, Int-b. Further evolution from Int-b leads mainly to 3-b1. However, 2 is the thermodynamically preferred product and is obtained at high temperatures, in agreement with the experimental observations. Regarding the BET analysis along path b, the breaking/forming process is described by four structural stability domains (SSDs) during the first step, which can be summarized as follows: (1) the breaking of the C-O bond with the transfer of its population to the lone pair (V(O)), (2) the reorganization of the electron density with the creation of two V(C) basins, and (3) the formation of a new C-C single bond via the merger of the two previous V(C) basins. Finally, the conversion of Int-b (via TS2-b1) occurs via the reorganization of the electron density during the first stage (the creation of different pseudoradical centers on the carbon atoms as a result of the depopulation of the C-C double bond involved in the formation of new single bonds), while the last stage corresponds to the non-concerted formation of the two new C-C bonds via the disappearance of the population of the four pseudoradical centers formed in the previous stage. On the other hand, along path a, the first step displays three SSDs, associated with the depopulation of the V(C2,C3) and V(C6,C7) basins, the appearance of the new monosynaptic basins V(C2) and V(C7), and finally the merging of these new monosynaptic basins through the creation of the C2-C7 single bond. The second step is described by a series of five SSDs, that account for the reorganization of the electron density within Int-a via the creation of four pseudoradical centers on the C12, C13, C3 and C6 carbon atoms. The last two SSDs deal with the formation of two C-C bonds via the merging of the monosynaptic basins formed in the previous domains.

The NCIWEB Server: A Novel Implementation of the Noncovalent Interactions Index for Biomolecular Systems

It is well-known that the activity and function of proteins is strictly correlated with their secondary, tertiary, and quaternary structures. Their biological role is regulated by their conformational flexibility and global fold, which, in turn, is largely governed by complex noncovalent interaction networks. Because of the large size of proteins, the analysis of their noncovalent interaction networks is challenging, but can provide insights into the energetics of conformational changes or protein-protein and protein-ligand interactions. The noncovalent interaction (NCI) index, based on the reduced density gradient, is a well-established tool for the detection of weak contacts in biological systems. In this work, we present a web-based application to expand the use of this index to proteins, which only requires a molecular structure as input and provides a mapping of the number, type, and strength of noncovalent interactions. Structure preparation is automated and allows direct importing from the PDB database, making this server (https://nciweb.dsi.upmc.fr) accessible to scientists with limited experience in bioinformatics. A quick overview of this tool and concise instructions are presented, together with an illustrative application.

5-Amino-2-aryl-2H-1,2,3-triazole-4-carboxamides: Unique AIEE-gens and selective Hg2+ fluorosensors

A series of fluorescent sensors based on small molecule were designed and fully characterised, demonstrating AIEE effect and revealing an outstanding ability to selectively detect Hg²⁺ ions. The structural and electronic properties were studied through quantum chemical calculations at (Time-Dependent) Density Functional Theory ((TD)-DFT) level. Carboxamides of 2-Aryl-1,2,3-Triazoles (CATs) showed significant differences in their photophysical properties depending on the structure of the substituent at amino function on the C5-atom in the heterocycle. When the tert-cycloalkylamino group (pyrrolidine, piperidine, azepane) was attached, the triazoles exhibited highly intensive blue fluorescence, with quantum yields (QYs) up to 95 % and lifetime up to 6.9 ns in different solvents, whereas the QYs of congeners bearing secondary alkylaminogroups (viz., NHMe, NHC₆H₁₁-cyclo) indicate low QYs (1-10 %). Nevertheless, all types of the obtained fluorophores demonstrated excellent AIEE effect and formed fluorescent nanoparticles in a binary mixtures of organic solvents and water. The introduction of the carboxamide function enhances the sensing properties of 2-aryl-1,2,3-triazoles, providing a selective fluorescence quenching reaction in the presence of Hg²⁺. The fluorescence intensity of the CATs declines with the addition of 1.0 eq. of Hg²⁺ into DMSO-water (v/v, 1:9). The other cations used did not induce any appreciable changes in fluorescence intensity. The CATs form a complex with Hg²⁺ with highly specific detection for Hg²⁺ over other competitive metal ions: the detection limits were determined to be 0.23 and 0.15 μM for the CATs 1b and 2c. The reverse effect was registered with the addition of ethylene diamine sodium salt; meanwhile, the CATs demonstrated more effective coordination with Hg²⁺ in comparison with cysteine. This last finding, as well as the ability to detect Hg²⁺, is very valuable for application within biology and medicine.

Reduction of Np(VI) with hydrazinopropionitrile via water-mediated proton transfer

Effectively adjusting and controlling the valence state of neptunium (Np) is essential in its separation during spent fuel reprocessing. Hydrazine and its derivatives as free-salts can selectively reduce Np(VI) to Np(V). Reduction mechanisms of Np(VI) with hydrazine and four derivatives have been explored using multiple theoretical methods in our previous works. Herein, we examine the reduction mechanism of Np(VI) with hydrazinopropionitrile (NCCH₂N₂H₃) which exhibits faster kinetics than most other hydrazine derivatives probably due to its σ-π hyperconjugation effect. Free radical ion pathways I, II and III involving the three types of hydrazine H atoms were found that correspond to the experimentally established mechanism of reduction of two Np(VI) via initial oxidation to [NCCH₂N₂H₃]⁺˙, followed by conversion to NCCH₂N₂H (+2H₃O⁺) and ultimately to CH₃CN + N₂. Potential energy profiles suggest that the second redox stage is rate-determining for all three pathways. Pathway I with water-mediated proton transfer is energetically preferred for hydrazinopropionitrile. Analyses using the approaches of localized molecular orbitals (LMOs), quantum theory of atoms in molecules (QTAIM), and intrinsic reaction coordinate (IRC) elucidate the bonding evolution for the structures on the reaction pathways. The results of the spin density reveal that the reduction of the first Np(VI) ion is the outer-sphere electron transfer, while that of the second Np(VI) ion is the hydrogen transfer. This work offers new insights into the nature of reduction of Np(VI) by hydrazinopropionitrile via water-mediated proton transfer, and provides a basis for designing free-salt reductants for Np separations.

How do electron donating substituents affect the electronic structure, molecular topology, vibrational properties and intra- and intermolecular interactions of polyhalogenated pyridines?

Seven polyhalogenated pyridine derivatives bearing an amino or a hydroxyl group, either at the ortho or para position, were studied using a combined experimental and computational approach. The presence of an electron donating substituent strongly impacted on the geometry, electronic structure, electrostatic properties, molecular topology and vibrational characteristics of these compounds compared to the corresponding polyhalogenated pyridines. In particular the attention was focused on changes in wavenumbers, force constants and intensity of the seven in-plane Ring Normal Modes (RNMs). Due to the nature and position of the substituents, intra- and intermolecular interactions also underwent dramatic modifications, as revealed using Natural Bond Orbital (NBO) analysis, Non-Covalent Interaction (NCI) analysis and Atom-In-Molecule (AIM) theory. Raman and FT-IR spectra of these seven compounds were also collected in solid phase and rationalised by the simulated spectra for hydrogen bonding and/or π-π stacking based homodimers. The present study provides a strategy not only for the vibrational characterisation for the individual compounds, but also for shedding light on the ways of molecular packing in the molecular crystals or cocrystals involving these compounds.

Symmetric Spirenes: Promising Building Blocks for New Generation Opto-Electronic Materials

The spiroconjugated hydrocarbons, and in particular spirenes, show unique properties among the numerous π-conjugated materials; they are quite rigid systems, with a subsequently small excitation reorganisation energy, and hence are...

Polyhalogenated aminobenzonitriles vs. their co-crystals with 18-crown-6: amino group position as a tool to control crystal packing and solid-state fluorescence

Strengthening (para-isomers) or weakening (ortho-isomers) of π-electron aggregation due to the crystal structure rearrangement results in the bathochromic or hypsochromic shift of the fluorescence maximum.

Kinetics and mechanism of the Barton–Kellogg olefination: a computational DFT study using CTST theory and topological approaches

Gibbs energies (kcal mol−1) for the BK reaction starting from R1 and R2, calculated at the MN15-L/Def2-TZVP level of theory in toluene as solvent (SMD) at 298 K for the first step and at 383.6 K for the consecutive steps.

Solvatomorphs of (Bu4N)2[{Ag(N2-py)}2Mo8O26]: structure, colouration and phase transition

(Bu4N)2[β-{Ag(N2-py)}2Mo8O26] demonstrates monomer/polymer dualism and a colouration phenomenon. The polymeric phase reveals a Ag assisted phase transition. Such complexes can act as precursors for catalytically active materials.

Two Approaches for the Synthesis of Fused Dihydropyridines via a 1,6-Electrocyclic Reaction: Fluorescent Properties and Prospects for Application

Reactions of penta-2,4-dienethioamides with acetylenedicarboxylic acid, methyl and ethyl esters, and methyl propiolate were systematically studied, and a number of new 2,3-dihydro-5H-thiazolo[3,2-a]pyridines (DTPs) and 4H,6H-pyrido[2,1-b][1,3]thiazines (PTZs) were prepared. A possible mechanism for a multistep domino transformation is suggested, and the key step is the 1,6-electrocyclic reaction. An additional alternative method for the synthesis of new heterocyclic systems was achieved. Evidence of the electrocyclic mechanism of a key step was collected from the analysis of the spatial structure of the synthesized bicyclic nonaromatic pyridines by X-ray diffraction and quantum chemical calculations, as well as from the thermodynamic quantities. DTPs exhibited yellow fluorescence in solution and yellow to red emissions in the solid state. Biological investigations demonstrated the ability of DTPs to penetrate living and fixed cells and presumably accumulate in lysosomes.

Deciphering the Curly Arrow Representation and Electron Flow for the 1,3-Dipolar Rearrangement between Acetonitrile Oxide and (1S,2R,4S)-2-Cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl Acetate Derivatives

This study is focused on describing the molecular mechanism beyond the molecular picture provided by the evolution of molecular orbitals, valence bond structures along the reaction progress, or conceptual density functional theory. Using bonding evolution theory (BET) analysis, we have deciphered the mechanism of the 1,3-dipolar rearrangement between acetonitrile oxide and (1S,2R,4S)-2-cyano-7-oxabicyclo[2.2.1]hept-5-en-2-yl acetate derivatives. The BET study revealed that the formation of the C-C bond takes place via a usual sharing model before the O-C one that is also formed in the halogenated species through a not very usual sharing model. The mechanism includes depopulation of the electron density at the N-C triple bond and creation of the V(N) and V(C) monosynaptic basins, depopulation of the former C-C double bond with the creation of V(C,C) basins, and final formation of the V(O,C) basin associated with the O-C bond. The topological changes along the reaction pathway take place in a highly synchronous way. BET provides a convenient quantitative method for deriving curly arrows and electron flow representation to unravel molecular mechanisms.

Structural Characterization, DFT Calculation, NCI, Scan-Rate Analysis and Antifungal Activity against Botrytis cinerea of (E)-2-{[(2-Aminopyridin-2-yl)imino]-methyl}-4,6-di-tert-butylphenol (Pyridine Schiff Base)

Botrytis cinerea is a ubiquitous necrotrophic filamentous fungal phytopathogen that lacks host specificity and can affect more than 1000 different plant species. In this work, we explored L1 [(E)-2-{[(2-aminopyridin-2-yl)imino]-methyl}-4,6-di-tert-butylphenol], a pyridine Schiff base harboring an intramolecular bond (IHB), regarding their antifungal activity against Botrytis cinerea. Moreover, we present a full characterization of the L1 by NMR and powder diffraction, as well as UV–vis, in the presence of previously untested different organic solvents. Complementary time-dependent density functional theory (TD-DFT) calculations were performed, and the noncovalent interaction (NCI) index was determined. Moreover, we obtained a scan-rate study on cyclic voltammetry of L1. Finally, we tested the antifungal activity of L1 against two strains of Botrytis cinerea (B05.10, a standard laboratory strain; and A1, a wild type strains isolated from Chilean blueberries). We found that L1 acts as an efficient antifungal agent against Botrytis cinerea at 26 °C, even better than the commercial antifungal agent fenhexamid. Although the antifungal activity was also observed at 4 °C, the effect was less pronounced. These results show the high versatility of this kind of pyridine Schiff bases in biological applications.

Arene-Ruthenium(II) Complexes Containing 11H-Indeno[1,2-b]quinoxalin-11-one Derivatives and Tryptanthrin-6-oxime: Synthesis, Characterization, Cytotoxicity, and Catalytic Transfer Hydrogenation of Aryl Ketones

A series of novel mono- and binuclear arene-ruthenium(II) complexes [(p-cym)Ru(L)Cl] containing 11H-indeno[1,2-b]quinoxalin-11-one derivatives or tryptanthrin-6-oxime were synthesized and characterized by X-ray crystallography, IR, NMR spectroscopy, cyclic voltammetry, and elemental analysis. Theoretical calculations invoking singlet state geometry optimization, solvation effects, and noncovalent interactions were done using density functional theory (DFT). DFT calculations were also applied to evaluate the electronic properties, and time-dependent DFT was applied to clarify experimental UV-vis results. Cytotoxicity for cancerous and noncancerous human cell lines was evaluated with cell viability MTT assay. Complexes demonstrated a moderate cytotoxic effect toward cancerous human cell line PANC-1. The catalytic activity of the complexes was evaluated in transfer hydrogenation of aryl ketones. All complexes exhibited good catalytic activity and functional group tolerance.

Real-Space Approach to the Reaction Force: Understanding the Origin of Synchronicity/Nonsynchronicity in Multibond Chemical Reactions

In this article, we present a complementary analysis based on the reaction force F(ξ)/reaction force constant κ(ξ) and noncovalent interactions (NCI) index to characterize the energetics (kinetic and thermodynamics) and mechanistic pathways of two sets of multibond chemical reactions, namely, two double-proton transfer and two Diels-Alder cycloaddition reactions. This approach offers a very straightforward and useful way to delve into a deeper understanding of this type of process. While F(ξ) allows the partition of the whole pathway into three regions or phases, κ(ξ) describes how orchestrated are the bond-breaking and bond-formation events. In turn, NCI indicates how the inter- and intramolecular bonds evolve. The most innovative aspect is the inclusion of the formation of the reactant complex along the pathway, which, by means of NCI, unveils the early molecular recognition and the comprehension of its role in determining the degree of the synchronicity/nonsynchronicity of one-step processes. This approach should be a useful and alternative tool to characterize the energetics and the mechanism of general chemical reactions.

Unravelling the kinetics and molecular mechanism of the degenerate Cope rearrangement of bullvalene

The kinetics and molecular mechanism of the gas phase degenerate Cope rearrangement (DCR) of bullvalene have been investigated by applying quantum mechanical calculations.

Fluorescent boron complexes based on new N,O-chelates as promising candidates for flow cytometry

This study presents the synthesis and optical properties of a new class of bright green-yellow fluorescent dyes with potential applications in bioimaging. A facile synthetic route via the chelation of aryl(hetaryl)aminoacryloylthiophene scaffolds with a BF2 fragment is presented. The photophysical properties of the dyes are attributed to the nature and position of electron-donating and electron-withdrawing substituents. Upon coordination to a BF2 fragment, characteristic emission was observed, with λem ranging from 503 to 543 nm and quantum yields of 0.14-0.42. Compared with parent aryl(hetaryl)aminoacryloylthiophenes, a significant red shift in absorption (up to 480 nm in solution) and emission (up to 543 nm in solution and 610 nm in the solid state) and high chemical stability and photostability were observed. The electron-accepting character of the substituents on the terminal aromatic ring or replacing this fragment with pyridine or pyrazine moieties resulted in increased quantum yields. To gain insight into the electronic structures and optical properties, quantum mechanical calculations were performed. The results of (TD-)DFT calculations supported the structural and spectroscopic data and showed the features of electronic distribution in the frontier molecular orbitals and active electrophilic and nucleophilic sites in the compounds investigated. Synthesized BF2 complexes are promising dyes for cell imaging and flow cytometry owing to their ready penetration and accumulation in cells.

The impact on the ring related vibrational frequencies of pyridine of hydrogen bonds with haloforms – a topology perspective

An intermolecular ring structure is identified for the hydrogen bonding system of pyridine and haloforms.

Impact of molecular packing rearrangement on solid-state fluorescence: polyhalogenated N-hetarylamines vs. their co-crystals with 18-crown-6

Relationship between the hetarylamine chemical structure, crystal packing in homo- and co-crystals, and fluorescence effects (quenching, bathochromic and hypsochromic shifts).

An effective and facile synthesis of new blue fluorophores on the basis of an 8-azapurine core

A convenient synthesis of 2-aryl-2,4-dihydro-5H-[1,2,3]triazolo[4,5-d]pyrimidin-5-ones (DTPs) from 3,3-diamino-2-(arylazo)acrylonitriles through a versatile and readily accessible two-step procedure is described. Density functional theory (DFT) calculations were performed to explain the selectivity of the heterocyclization step, which predominantly afforded 6-amino-5-(arylazo)pyrimidin-2(1H)-thiones in chloroform or ethanol, and 2,3-dihydro-1,2,4-triazines in toluene or DMF. Novel 2-aryl-2,4-dihydro-5H-[1,2,3]triazolo[4,5-d]pyrimidin-5-ones were obtained in good yields and showed absorption in the ultraviolet region and good emission in the blue region. The photophysical properties of DTPs were better than those cited in select literature examples of 8-azapurines. Owing to the facile synthesis and good photophysical characteristics in an aqueous medium, the new DTPs should have potential applications as organic fluorophores in fluorescence imaging and materials science.

Curly arrows, electron flow, and reaction mechanisms from the perspective of the bonding evolution theory

Despite the usefulness of curly arrows in chemistry, their relationship with real electron density flows is still imprecise, and even their direct connection to quantum chemistry is still controversial. The paradigmatic description - from first principles - of the mechanistic aspects of a given chemical process is based mainly on the relative energies and geometrical changes at the stationary points of the potential energy surface along the reaction pathway; however, it is not sufficient to describe chemical systems in terms of bonding aspects. Probing the electron density distribution during a chemical reaction can provide important insights, enabling us to understand and control chemical reactions. This aim has required an extension of the relationships between the concepts of traditional chemistry and those of quantum mechanics. Bonding evolution theory (BET), which combines the topological analysis of the electron localization function (ELF) and Thom's catastrophe theory (CT), provides a powerful method that offers insight into the molecular mechanism of chemical rearrangements. In agreement with the laws of physical and aspects of quantum theory, BET can be considered an appropriate tool to tackle chemical reactivity with a wide range of possible applications. In this work, BET is applied to address a long-standing problem: the ability to monitor the flow of electron density. BET analysis shows a connection between quantum mechanics and bond making/forming processes. Likewise, the present approach retrieves the classical curly arrows used to describe the rearrangements of chemical bonds and provides detailed physical grounds for this type of representation. We demonstrate this procedure using the test set of prototypical examples of thermal ring apertures, and the degenerated Cope rearrangement of semibullvalene.

A bonding evolution analysis for the thermal Claisen rearrangement: an experimental and theoretical exercise for testing the electron density flow

The BET analysis brings about the natural appearance of curly arrows representing thus the electronic flow in molecular rearrangements.

Ultrafast excited state decay of natural UV filters: from intermolecular hydrogen bonds to a conical intersection

An unsaturated bond in the side chain leads to the ultrafast decay of the excited statesviaa conical intersection independent of solvent properties.

A topological study of chemical bonds under pressure: solid hydrogen as a model case

It is now well recognized that a fundamental understanding of the rules that govern chemistry under pressure is still lacking. Hydrogen being the "simplest" element as well as a central core to high pressure physics, we undertake a general study of the changes in the chemical bonding under pressure. We start from a simple trimer unit that has been found in high pressure phases, whose behavior has been found to reveal the basics of hydrogen polymerization under pressure. Making use of bond analysis tools, mainly the NCI (noncovalent interactions) index, we show that polymerization takes place in three steps: dipolar attraction, repulsion and bond formation. The use of a 1D Wigner-Seitz radius allowed us to extend the conclusions to 3D networks and to analyze their degree of polymerization. On the one hand, this approach provides new insight into the polymerization of hydrogen. On the other hand, it shows that complicated molecular solids can be understood from cluster models, where correlated methods can be applied, main differences in solid state arising at the transition points, where breaking/forming of bonds happens at once instead of continuously like in the cluster model.

Introducing topology to assess the synchronicity of organic reactions. Dual reactivity of oximes with alkenes as a case study

Quantum chemical topology analyses provide a new way of understanding the synchronicity of organic reactions.

New mechanistic interpretations for nitrone reactivity

The reactivity of nitrones in cycloadditions and related reactions is revisited by introducing a topological perspective.

Curly arrows meet electron density transfers in chemical reaction mechanisms: from electron localization function (ELF) analysis to valence-shell electron-pair repulsion (VSEPR) inspired interpretation

The displacement of the nuclei along the reaction path provides an explanatory interpretation of the electron density transfers making possible to understand chemical reactions.