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The term hypercoordination refers to the extent of the coordination of an element by its normal value. In the hypercoordination sphere, the element can achieve planar and/or non-planar molecular shape. Hence, planar hypercoordinate carbon species violate two structural rules: (i) The highest coordination number of carbon is four and (ii) the tetrahedral orientation by the connected elements and/or groups. The unusual planar orientations are mostly stabilized by the electronic interactions of the central atom with the surrounding ligands. In this review article, we will talk about the current progress in the theoretical prediction of viable planar hypercoordinate carbon compounds. Primary knowledge of the planar hypercoordinate chemistry will lead to its forthcoming expansion. Experimental and theoretical interests in planar tetracoordinate carbon (ptC), planar pentacoordinate carbon (ppC), and planar hexacoordinate carbon (phC) are continued. The proposed electronic and mechanical strategies are helpful for the designing of the ptC compounds. Moreover, the 18-valence electron rule can guide the design of new ptC clusters computationally as well as experimentally. However, the counting of 18-valence electrons is not a requisite condition to contain a ptC in a cluster. Furthermore, this ptC idea is expanded to the probability of a greater coordination number of carbon in planar orientations. Unfortunately, until now, there are no such logical approaches to designing ppC, phC, or higher-coordinate carbon molecules/ions. There exist a few global minimum structures of phC clusters identified computationally, but none have been detected experimentally. All planar hypercoordinate carbon species in the global minima may be feasible in the gas phase.

In order to examine the effect of oriented (static) electric fields (OEF) on the kinetics of some representative Suzuki–Miyaura and metal-cluster mediated reactions at ambient temperatures, density functional theory-based calculations are reported herein. Results indicate that, in general, OEF can facilitate the kinetics of the concerned reactions when applied along the suitable direction (parallel or anti-parallel with respect to the reaction axis). The reverse effect happens if the direction of the OEF is flipped. OEF (when applied along the ‘right’ direction) helps to polarize the transition states in the desired direction, thereby facilitating favorable bonding interactions. Given the growing need for finding appropriate catalysts among the scientific community, OEF can prove to be a vital route for the same.

This article provides a discussion on the nature of bonding between noble gases (Ng) and noble metals (M) from a quantum chemical perspective by investigating compounds such as NgMY (Y=CN, O, NO3, SO4, CO3), [NgM−(bipy)]+, NgMCCH, and MCCNgH complexes, where M=Cu, Ag, Au and Ng=Kr−Rn, with some complexes containing the lighter noble gas atoms as well. Despite having very low chemical reactivity, noble gases have been observed to form weak bonds with noble metals such as copper, gold, and silver. In this study, we explore the factors that contribute to this unusual bonding behavior, including the electronic structure of the atoms involved and the geometric configuration of the concerned fragments. We also investigate the metastable nature of the resulting complexes by studying the energetics of their possible dissociation and internal isomerization channels. The noble gas-binding ability of the bare metal cyanides are higher than most of their bromide counterparts, with CuCN and AgCN showing higher affinity than their chloride analogues as well. In contrast, the oxides seem to have lower binding power than their corresponding halides. In the oxide and the bipyridyl complexes, the Ng-binding ability follows the order Au > Cu > Ag. The dissociation energies calculated, considering the zero-point energy correction for possible dissociation channels, increase as we move down the noble gas group. The bond between the noble gases and the noble metals in the complexes are found to have comparable weightage of orbital and electrostatic interactions, suggestive of a partial covalent nature. The same is validated from the topological analysis of electron density.

Concurrence of aromaticity and hydrogen trapping potential of some atomic clusters has drawn the attention of scientific community, although in a few cases it has been reported that the partial charges on the constituent atoms of the clusters are probably responsible for H2 trapping via frail van der Waals type of interactions. In this article, an effort is made to review the studies which address the conjunction of aromaticity and hydrogen storage potential of different atomic clusters and the contribution of our research group to this particular topic.

The scientific community is engrossed in the thought of a probable solution to the future energy crisis keeping in mind a better environment-friendly alternative. Although there are many such alternatives, the green hydrogen energy has occupied most of the brilliant minds due to its abundance and numerous production resources. For the advancement of hydrogen economy, Government agencies are funding pertinent research projects. There is an avalanche of molecular systems which are studied by several chemists for storing atomic and molecular hydrogens. The present review on molecular hydrogen storage focuses on all-metal and nonmetal aromatic clusters. In addition to the effect of aromaticity on hydrogen trapping potential of different molecular moieties, the importance of using the conceptual density functional theory based reactivity descriptors is also highlighted. Investigations from our group have been revealing the fact that several aromatic metal clusters, metal doped nonmetal clusters as well as pure nonmetal clusters can serve as potential molecular hydrogen trapping agents. Reported systems include N4Li2, N6Ca2 clusters, Mgn, and Can (n = 8–10) cage-like moieties, B12N12 clathrate, transition metal doped ethylene complexes, M3+ (M = Li, Na) ions, E3-M2 (E = Be, Mg, Al; M = Li, Na, K) clusters, Li3Al4− ions, Li decorated star-like molecules, BxLiy (x = 3–6; y = 1, 2), Li-doped annular forms, Li-doped borazine derivatives, C12N12 clusters (N4C3H)6Li6 and associated 3-D functional material, cucurbiturils, lithium–phosphorus double-helices. Ni bound C12N12 moieties are also reported recently.

A density functional theory study is performed to determine the stability and bonding in the neon dimer inside the B30N30 fullerene cage, the fluxional B40 cage, and within non-fluxional cages such as B12N12 and C60. The nature of bonding in the Ne2 encapsulated B40 is compared with the that in other cages in an attempt to determine whether any possible alterations are brought about by the dynamical nature of the host cage apart from the associated confinement effects. The bonding analysis includes the natural bond order (NBO), Bader’s Atoms-in-Molecules electron density analysis (AIM), and energy decomposition analysis (EDA), revealing the non-covalent nature of the interactions between the Ne atoms and that between the Ne and the cage atoms. The formation of all the Ne2@cage systems is thermochemically unfavourable, the least being that for the B30N30 cage, which can easily be made favourable at lower temperatures. The Ne-Ne distance is lowest in the smallest cage and increases as the cage size increase due to steric relaxation experienced by the dimer. The dynamical picture of the systems is investigated by performing ab initio molecular dynamics simulations using the atom-centred density matrix propagation (ADMP) technique, which shows the nature of the movement of the dimer inside the cages, and by the fact that since it moves as a single entity, a weak bonding force holds them together, apart from their proven kinetic stability.

The preclinical drug discovery stage often requires a large amount of costly and time-consuming experiments using huge sets of chemical compounds. In the last few decades, this process has undergone significant improvements by the introduction of quantitative structure-activity relationship (QSAR) modelling that uses a certain percentage of experimental data to predict the biological activity/property of compounds with similar structural skeleton and/or containing a particular functional group(s). The use of machine learning tools along with it has made life even easier for pharmaceutical researchers. Here, we discuss the toxicity of certain sets of bioactive compounds towards Pimephales promelas and Tetrahymena pyriformis in terms of the global conceptual density functional theory (CDFT)-based descriptor, electrophilicity index (ω). We have compared the results with those obtained by using the commonly used hydrophobicity parameter, logP (where P is the n-octanol/water partition coefficient), considering the greater ease of computing the ω descriptor. The Human African trypanosomiasis (HAT) curing activity of 32 pyridyl benzamide derivatives is also studied against Tryphanosoma brucei. In this review article, we summarize these multiple linear regression (MLR)-based QSAR studies in terms of electrophilicity (ω, ω2) and hydrophobicity (logP, (logP)2) parameters.

The chemistry of frustrated Lewis pair (FLP) is widely explored in the activation of small molecules, the hydrogenation of CO2, and unsaturated organic species. A survey of several experimental works on the activation of small molecules by FLPs and the related mechanistic insights into their reactivity from electronic structure theory calculation are provided in the present review, along with the catalytic hydrogenation of CO2. The mechanistic insight into H2 activation is thoroughly discussed, which may provide a guideline to design more efficient FLP for H2 activation. FLPs can activate other small molecules like, CO, NO, CO2, SO2, N2O, alkenes, alkynes, etc. by cooperative action of the Lewis centers of FLPs, as revealed by several computational analyses. The activation barrier of H2 and other small molecules by the FLP can be decreased by utilizing the aromaticity criterion in the FLP as demonstrated by the nucleus independent chemical shift (NICS) analysis. The term boron-ligand cooperation (BLC), which is analogous to the metal-ligand cooperation (MLC), is invoked to describe a distinct class of reactivity of some specific FLPs towards H2 activation.

Abstract The activation of H2 by pyramidalized boron‐based frustrated Lewis Pairs (FLPs) (B/E‐FLP systems where “E” refers to N, P, As, Sb, and Bi) have been explored using density functional theory (DFT) based computational study. The activation pathway for the entire process is accurately characterized through the utilization of the activation strain model (ASM) of reactivity, shedding light on the underlying physical factors governing the process. The study also explores the hydrogenation process of multiple bonds with the help of B/N‐FLP. The research findings demonstrate that the liberation of activated dihydrogen occurs in a synchronized, albeit noticeably asynchronous, fashion. The transformation is extensively elucidated using the activation strain model and the energy decomposition analysis. This approach suggests a co‐operative double hydrogen‐transfer mechanism, where the B−H hydride triggers a nucleophilic attack on the carbon atom of the multiple bonds, succeeded by the migration of the protic N−H.