N-Arylation of Protected and Unprotected 5-Bromo 2-Aminobenzimidazole as Organic Material: Non-Linear Optical (NLO) Properties and Structural Feature Determination through Computational Approach

The interest in the NLO response of organic compounds is growing rapidly, due to the ease of synthesis, availability, and low loss. Here, in this study, Cu(II)-catalyzed selective N-arylation of 2-aminobenzoimidazoles derivatives were achieved in the presence of different bases Et3N/TMEDA, solvents DCM/MeOH/H2O, and various aryl boronic acids under open atmospheric conditions. Two different copper-catalyzed pathways were selected for N-arylation in the presence of active nucleophilic sites, providing a unique tool for the preparation of NLO materials, C-NH (aryl) derivatives of 2-aminobenzoimidazoles with protection and without protection of NH2 group. In addition to NMR analysis, all synthesized derivatives (1a–1f and 2a–2f) of 5-bromo 2-amino benzimidazole (1) were computed for their non-linear optical (NLO) properties and reactivity descriptor parameters. Frontier molecular orbital (FMO) analysis was performed to get information about the electronic properties and reactivity of synthesized compounds.

Regio-Selectivity Prediction with a Machine-Learned Reaction Representation and On-the-Fly Quantum Mechanical Descriptors

<div> <div> <div> <p>We introduce a new method that combines machine-learned reaction representation with selected quantum mechanical descriptors to predict regio-selectivity in general substitution reactions. We construct a reactivity descriptor database based on ab initio calculations of 130k organic molecules, and train a multi-task constrained model to calculate demanded descriptors on-the-fly. </p> </div> </div> </div>

Regio-Selectivity Prediction with a Machine-Learned Reaction Representation and On-the-Fly Quantum Mechanical Descriptors

<div> <div> <div> <p>We introduce a new method that combines machine-learned reaction representation with selected quantum mechanical descriptors to predict regio-selectivity in general substitution reactions. We construct a reactivity descriptor database based on ab initio calculations of 130k organic molecules, and train a multi-task constrained model to calculate demanded descriptors on-the-fly. </p> </div> </div> </div>

Conceptual DFT Reactivity Descriptors Computational Study of Graphene and Derivatives Flakes: Doped Graphene, Graphane, Fluorographene, Graphene Oxide, Graphyne, and Graphdiyne

Allotropes of carbon such as graphene, graphane, fluorographene, doped graphene with N, B or P, graphene oxide, graphyne, and graphdiyne were studied through conceptual DFT reactivity descriptor indexes. To understand their chemical behavior and how they interact with different types of molecules, for instance, drugs (due to their potential use in drug carrier applications). This work shows the results of the changes in the global and local reactivity descriptor indexes and geometrical characteristics within the different graphene derivatives and rationalizes how they can interact with small molecules. Molecular hardness, the ionization energy, the electron affinity, electrodonating power index, and electroaccepting power indexes are the computed global reactivity descriptors. While, fukui functions, local softness, and molecular electrostatic potential are the local reactivity descriptors. The results suggest that the hybridization of carbons in the derivatives is kept close to sp3, while for graphene is sp2, the symmetry changes have as consequence changes in their chemical behavior. We found that doping with B or P (one or two atoms doped) and functionalizing with -OH or -COOH groups (as in graphene oxide), decreases the ionization energy in water solvent calculations, allowing for easier electron donation. On the other hand, doping with N atoms and functionalizing with F atoms increases the electron affinity. These types of changes enhance the chemisorption or physisorption by non-covalent interactions and covalent interactions with small molecules, principally, in the carbon atoms nearest to the doped/functionalized atom. Resumen. Los alótropos de carbono como el grafeno, el grafano, el fluorografeno, el grafeno dopado con N, B o P, el óxido de grafeno, el grafino y el grafidiino se estudiaron mediante los índices de los descriptores de reactividad de la DFT conceptual. Ello, para comprender su comportamiento químico y cómo interactúan con diferentes tipos de moléculas, por ejemplo, fármacos (debido a su posible uso en aplicaciones como transportadores de fármacos). Este trabajo muestra los resultados de los cambios en los índices de los descriptores de reactividad global y local y las características geométricas de los diferentes derivados de grafeno y, predice cómo podrián interactuar con moléculas pequeñas. La dureza molecular, la energía de ionización, la afinidad electrónica, el índice de potencia electrodonadora y electroaceptora son los descriptores DFT de reactividad global calculados. Mientras que las funciones de fukui, la suavidad local y el potencial electrostático molecular son los descriptores de reactividad local. Los resultados sugieren que la hibridación de los carbonos en los derivados se mantiene cerca de sp3, mientras que para el grafeno es sp2, los cambios de simetría tienen como consecuencia cambios en su comportamiento químico. Descubrimos que el dopaje con B o P (uno o dos átomos dopados) y la funcionalización con grupos -OH o -COOH (como en el óxido de grafeno), disminuye la energía de ionización en los cálculos de solvente con agua, lo que permite una donación de electrones más fácil. Por otro lado, el dopaje con átomos de N y la funcionalización con átomos de F aumenta la afinidad electrónica. Estos tipos de cambios mejoran la quimisorción o fisisorción por interacciones no covalentes e interacciones covalentes con moléculas pequeñas, principalmente en los átomos de carbono más cercanos al átomo dopado/funcionalizado.

A new approach to compute atomic electrophilicity index in terms of Gordy’s electronegativity

Electrophilicity index is a well-known Conceptual Density Functional Theory–based reactivity descriptor to explain a wide range of physicochemical behaviours. In the present work, an attempt is made to evaluate a new electrophilicity index scale in terms of nucleophilicity index relying on Gordy’s electronegativity scale. The computation is performed for 103 elements of the periodic table invoking regression analysis. The new set of electrophilicity index satisfies the sine qua non of a standard scale. Electrophilicity Equalization Principle is also validated by our computed data. It is put forward that the new scale will be useful in understanding various physicochemical properties and related phenomenon.

Active centre and reactivity descriptor of a green single component imidazole catalyst for acetylene hydrochlorination

The mechanisms and reactivities of imidazole-catalyzed acetylene hydrochlorination have been investigated by combined computational and experimental studies.