Beyond the triple bond: unlocking dinitrogen activation with tailored superbase phosphines.

Activating atmospheric dinitrogen (N), a molecule with a remarkably strong triple bond, remains a major challenge in chemistry. This theoretical study explores the potential of superbase phosphines, specifically those decorated with imidazolin-2-imine ((ImN)P) and imidazolin-2-methylidene ((ImCH)P) to facilitate N activation and subsequent hydrazine (HNNH) formation. Using density functional theory (DFT) at the M06L/6-311++G(d,p) level, we investigated the interactions between these phosphines and N.

From loose to tight: unveiling bond stretch isomerism in π-complexes of Li, Na and K.

The study investigates the phenomenon of bond stretch isomerism (BSI) in complexes formed between alkali metals (Li, Na, K) and various non-aromatic, aromatic hydrocarbons, as well as heteroaromatic systems. The research employs density functional theory (DFT) calculations to optimize complex geometries and analyze their electronic structures using molecular electrostatic potential (MESP), charge, and spin density analyses. The results reveal that these complexes can exist in two distinct configurations: 'loose' long-bond isomers (lbi) that retain the original hydrocarbon geometry and 'tight' short-bond isomers (sbi) that undergo geometrical distortion upon complexation, with sbi generally being more stable.

Cooperative Noncovalent Interactions Controlling Amine-Catalyzed Aldol Reaction Pathways Catalyzed by the Bifunctional Amino Quaternary Phosphonium Ion.

Members of a new class of bifunctional amino quaternary phosphonium salts have been synthesized and utilized as catalysts in aldol condensation reactions, as demonstrated herein. These secondary amines feature a phosphonium ion connected by a carbon chain, enabling the quaternary phosphonium ion to engage in distinct cooperative noncovalent interactions. These interactions work in tandem to stabilize different transition state complexes, exclusively controlling competing amine-catalyzed aldol pathways via the Mannich mechanism.

Gold(I) Catalysis in Alkyne-Alkene Reactions: A Systematic Exploration through Molecular Electrostatic Potential Analysis.

Gold catalysis enables selective chemical transformations with catalytic activity tunable through ligand selection. This study uses the density functional theory (DFT) to explore the impact of phosphine ligands (PR) on gold(I)-catalyzed alkyne-alkene cyclobutene formation. We analyze the following key steps: (i) PR-Au complexation, (ii) alkyne binding, (iii) alkene binding, (iv) C-C coupling transition state, (v) cyclobutene formation transition state, and (vi) cyclobutene dissociation.

Direct Estimation of Aromatization Energy from H NMR and UV-Vis Absorption Data of Homodesmotic Molecules.

This study delves into the ring-opening reaction of two distinct diaryl-ring-pyran systems, referred to as and , where the term 'ring' encompasses aromatic, nonaromatic, or antiaromatic motifs. These systems transform into the corresponding quinonoid systems, denoted as - and -. Homodesmotic pairs (, ) and (-, -) are categorized as (aromatic, nonaromatic), (aromatic, partially aromatic), (antiaromatic, nonaromatic), and (nonaromatic, nonaromatic), with their energy difference representing aromatization energy ().

Utilization of the through-space effect to design donor-acceptor systems of pyrrole, indole, isoindole, azulene and aniline.

Molecular electrostatic potential (MESP) topology analysis reveals the underlying phenomenon of the through-space effect (TSE), which imparts electron donor-acceptor properties to a wide range of chemical systems, including derivatives of pyrrole, indole, isoindole, azulene, and aniline. The TSE is inherent in pyrrole owing to the strong polarization of electron density (PoED) from the formally positively charged N-center to the CC bonding region. The N → CC directional nature of the TSE has been effectively employed to design molecules with high electronic polarization, such as bipyrroles, polypyrroles, phenyl pyrroles, multi-pyrrolyl systems and N-doped nanographenes.

Unraveling pnicogen bonding cooperativity: Insights from molecular electrostatic potential analysis.

A theoretical investigation on the cooperativity of a series of binary, ternary, and quaternary complexes interconnected by pnicogen bonds has been conducted using calculations at the M06-2X/aug-cc-pVTZ level of density functional theory. By measuring changes in the molecular electrostatic potential (MESP) at the nucleus of interacting atoms in all of the complexes, it is possible to quantify the substantial reorganization of the electron density triggered by the formation of pnicogen bonds. The positive change in MESP, indicating a loss of electron density from the donor molecule in a dimer, facilitates the acceptance of electron density from a third molecule, resulting in the formation of a ternary complex with a stronger pnicogen bond compared to the one present in the binary complex.

Topology of electrostatic potential and electron density reveals a covalent to non-covalent carbon-carbon bond continuum.

The covalent and non-covalent nature of carbon-carbon (CC) interactions in a wide range of molecular systems can be characterized using various methods, including the analysis of molecular electrostatic potential (MESP), represented as (), and the molecular electron density (MED), represented as (). These techniques provide valuable insights into the bonding between carbon atoms in different molecular environments. By uncovering a fundamental exponential relationship between the distance of the CC bond and the highest eigenvalue () of () at the bond critical point (BCP), this study establishes the continuum model for all types of CC interactions, including transition states.

Molecular Electrostatic Potential Topology Analysis of Noncovalent Interactions.

ConspectusThe topology of molecular electrostatic potential (MESP), (), derived from a reliable quantum chemical method has been used as a powerful tool for the study of intermolecular noncovalent interactions. The MESP topology mapping is achieved by computing both ∇() data and the elements of the Hessian matrix at ∇() = 0, the critical point. MESP minimum () as well as MESP at a reaction center, specific to an atom (), have been employed as electronic parameters to interpret the variations in the reactivity (activation/deactivation) of chemical systems with respect to the influence of substituents, ligands, π-conjugation, aromaticity, trans influence, hybridization effects, steric effects, cooperativity, noncovalent interactions, etc.

Hydrogen bonds of OCNH motif in rings in drugs: A molecular electrostatic potential analysis.

The OCNH unit is one of the most frequently encountered structural motifs in rings in drugs which serves dual role as the proton donor through NH bond and proton acceptor through the CO bond. Here, we predicted the HB strength (E ) of OCNH motif with H O for commonly observed 37 rings in drugs with DFT method M06L/6-311++G(d,p). The HB strength is rationalized in terms of molecular electrostatic potential (MESP) topology parameters ΔV and ΔV which describe the relative electron deficient/rich nature of NH and CO, respectively, with respect to the reference formamide.

Electrostatic Potential for Exploring Electron Delocalization in Infinitenes, Circulenes, and Nanobelts.

The π-conjugation, aromaticity, and stability of the newly synthesized 12-infinitene and of other infinitenes comprising 8-, 10-, 14-, and 16-arene rings are investigated using density functional theory. The π-electron delocalization and aromatic character rooted in infinitenes are quantified in terms of molecular electrostatic potential (MESP) topology. Structurally, the infinitene bears a close resemblance of its helically twisted structure to the infinity symbol.

Polycyclic Aromatic Hydrocarbons as Anode Materials in Lithium-Ion Batteries: A DFT Study.

The structure and energetics of the interactive behavior of Li and Li with polycyclic aromatic hydrocarbons (PAHs) have been studied at the wB97XD/6-311G(d,p) level of DFT. The electron distribution in the PAHs, analyzed using the topology of the molecular electrostatic potential (MESP), led to the categorization of their aromatic rings into five types, viz , , , , and . Among the different rings, sextet-type and naphthalene-type rings showed the highest interaction with Li.

Quantum chemical studies on the binding domain of SARS-CoV-2 S-protein: human ACE2 interface complex.

A two-layer ONIOM(B3LYP/6-31G*:PM7) method is used to model the binding of several drug/drug-like molecules () at the SARS-CoV-2 S-protein: human ACE2 protein interface cavity. The selected molecules include a set of thirty-five ligands from the study of Smith and Smith which showed a high docking score in the range of -7.0 to -7.

Polyanionic cyano-fullerides for CO capture: a DFT prediction.

The reaction of C fullerene with '' molecules ( = 1 to 6) of 1,3-dimethyl-2,3-dihydro-2-cyano-imidazole (IMCN) results in the exothermic formation of imidazolium cation-polyanionic fulleride complexes, (IM)⋯((C(CN))). The binding energy of IM with (C(CN)) in the imidazolium-fulleride ionic complexes increased from -69.6 kcal mol for = 1 to -202.

A novel aureothin diepoxide derivative from Streptomyces sp. NIIST-D31 strain.

A novel vicinal diepoxide of alloaureothin was isolated from Streptomyces sp. NIIST-D31 strain along with three carboxamides, p-aminobenzoic acid and 1,6-dimethoxyphenazine. Exhaustive 2D NMR analysis and analysis of experimental, theoretical CD spectra aided in establishing the structure of compound 1.

Demarcating Noncovalent and Covalent Bond Territories: Imine-CO Complexes and Cooperative CO Capture.

Chemical bond territory is rich with covalently bonded molecules wherein a strong bond is formed by equal or unequal sharing of a quantum of electrons. The noncovalent version of the bonding scenarios expands the chemical bonding territory to a weak domain wherein the interplay of electrostatic and π-effects, dipole-dipole, dipole-induced dipole, and induced dipole-induced dipole interactions, and hydrophobic effects occur. Here we study both the covalent and noncovalent interactive behavior of cyclic and acyclic imine-based functional molecules (XN) with CO.

Amplified Spontaneous Emission from Zwitterionic Excited-State Intramolecular Proton Transfer.

The unique four-level photocycle characteristics of excited-state intramolecular proton transfer (ESIPT) materials enable population inversion and large spectral separation between absorption and emission through their respective enol and keto forms. This leads to minimal or no self-absorption losses, a favorable feature in acting as an optical gain medium. While conventional ESIPT materials with an enol-keto tautomerism process are widely known, zwitterionic ESIPT materials, particularly those with high photoluminescence, are scarce.

Fulleride-metal η sandwich and multi-decker sandwich complexes: A DFT prediction.

The (C CN) formed by the reaction of CN with fullerene shows high electron rich character, very similar to C ˙ , and it behaves as a large anion. Similar to Cp , the bulky anion, (C CN) , acts as a strong η ligand towards transition metal centers. Previous studies on η coordination of fullerene cage are reported for pseudo fullerenes whereas the present study deals with sandwich complexes of (C CN) with Fe(II), Ru(II), Cr(II), Mo(II), and Ni(II) and multi-decker sandwich complexes of CN-fullerides with Fe(II).

NADH-depletion triggered energy shutting with cyclometalated iridium (III) complex enabled bimodal Luminescence-SERS sensing and photodynamic therapy.

The nicotinamide adenine dinucleotide-reduced (NADH) function as a hydride (H) carrier to maintain cellular homeostasis. Herein, we report a quinoline appended iridium complex (QAIC) as a molecular probe in fluorescence and surface-enhanced Raman spectroscopy (SERS) modalities to evaluate the endogenous NADH status. NADH-triggered activation of QAIC enabled luminescence (turn-ON) and SERS (turn-OFF) switching phenomenon with a detection limit of 25.

Hydration patterns of rings in drugs and relationship to lipophilicity: A DFT study.

Rings are one of the major scaffold components of drugs in medicinal chemistry, due to their unique electronic distribution, scaffold rigidity, and three-dimensionality while lipophilicity is considered as a vital parameter of rings that can influence the reactivity, metabolic stability, and toxicity. We have analyzed the electronic features, hydration patterns, solvation effect and lipophilicity data for 51 most widely used ring systems in drugs. Molecular electrostatic potential (MESP) topology analysis has been used to assess the electronic distribution in rings which provided an easy interpretation of the most suitable hydration patterns of the ring with H O molecule.

Dynamic self-assembly of mannosylated-calix[4]arene into micelles for the delivery of hydrophobic drugs.

Carbohydrate-lectin interactions and glycol-molecule-driven self-assembly are powerful yet challenging strategies to create supramolecular nanostructures for biomedical applications. Herein, we develop a modular approach of micellization with a small molecular mannosylated-calix[4]arene synthetic core, CA-Man3, to generate nano-micelles, CA-Man3-NPs, which can target cancer cell surface receptors and facilitate the delivery of hydrophobic cargo. The oligomeric nature of the calix[4]arene enables the dynamic self-assembly of calix[4]arene (CA), where an amphiphile, functionalized with mannose units (CA-glycoconjugates) in the upper rim and alkylated lower rim, afforded the CA-Man3-NPs in a controllable manner.

Imidazolium-fulleride ionic liquids - a DFT prediction.

Ionic liquids (ILs) exhibit tunable physicochemical properties due to the flexibility of being able to select their cation-anion combination from a large pool of ions. The size of the ions controls the properties of the ILs in the range from ionic to molecular, and thus large ions play an important role in regulating the melting temperature and viscosity. Here, we show that the exohedral addition of anionic X moieties to C (X = H, F, OH, CN, NH, and NO) is a thermodynamically viable process for creating large X-fulleride anions (CX).

Antiaromaticity-Aromaticity Interplay in Fused Benzenoid Systems Using Molecular Electrostatic Potential Topology.

The phenomenon of antiaromaticity-aromaticity interplay in aromatic-antiaromatic (A-aA)-fused systems is studied using molecular electrostatic potential (MESP) analysis, which clearly brings out the electron-rich π-regions of molecular systems. Benzene, naphthalene, phenanthrene, and pyrene are the aromatic units and cyclobutadiene and pentalene are the antiaromatic units considered to construct the A-aA-fused systems. The fused system is seen to reduce the antiaromaticity by adopting a configuration containing the least number of localized bonds over antiaromatic moieties.

Guanidine as a strong CO adsorbent: a DFT study on cooperative CO adsorption.

Among the various carbon capture and storage (CCS) technologies, the direct air capture (DAC) of CO2 by engineered chemical reactions on suitable adsorbents has attained more attention in recent times. Guanidine (G) is one of such promising adsorbent molecules for CO2 capture. Recently Lee et al.