Ashoka University is a private university located in Sonipat, Haryana, India, focusing on liberal arts and sciences. It was established in 2014.&nbsp;It is guided by an academic council of academics and scholars from around the world. The council sets the university&#39;s academic standard, advising on matters of curriculum, faculty hiring and research.&nbsp;

Ashoka University offers a full-time 3 (+ 1) year undergraduate programme. The University comprises of&nbsp;2500 plus students, with a mix of both national and international students.&nbsp; &nbsp;

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Ashoka University

Recent synthesis of sp-hybridized cyclo[18]carbon allotrope has attracted immense curiosity. Since then, a generous amount of theoretical studies concerning aromaticity, adsorption, and spectra of the molecule have been performed. However, very few stuides have been carried out concerning its reactivities and catalytic behaviour. In this article, a DFT-based inquisition has been reported regarding the reactivity of Si substituted cyclo[18]carbon molecule towards molecular N2. Results show that the Si substituted derivative is effective in producing adducts with molecular nitrogen. Charge calculations and IRC trapping methods indicate that only the Si center of C17Si and its (HOMO-1) level participate in N2 addition. The N-adduct so formed, is then found to spontaneously react with molecular H2. The addition of two H2 molecules to the activated nitrogen molecule to give respective amine derivatives have also been studied. The successful generation of the precursor of NH3 by C17Si lays a clear emphasis on its potentiality. © 2022 Wiley-VCH GmbH.

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Department of Chemistry

ChemPhysChem

Activation and Conversion of Molecular Nitrogen to the Precursor of Ammonia on Silicon Substituted Cyclo[18]Carbon: a DFT Design

The requirement of an efficient energy storage device has become an exclusive requisite for technological and scientific innovations. In the present work, by using the 2D monolayer semiconductor-semiconductor and semiconductor-metal lateral interface structures as the model structure, we performed periodic DFT calculations to examine the possibility of 2D MoS2-MoSe2 and MoS2-NbS2 lateral heterostructures (LHS) as the electrodes of a battery. The MoS2-MoSe2 lateral interface is a semiconductor, whereas the MoS2-NbS2 lateral interface preserves metallic character. Besides, we found that Li/Na ion adsorption is more influential on the lateral heterostructure and is exothermic, with ultrafast diffusion, and is comparable to their monolayers. Meanwhile, the calculated open-circuit voltage is enormously low, like other widely investigated pristine 2D materials. The enhanced electrical conductivity, short diffusion distances, minutely low equilibrium voltage with good stability, large theoretical capacity and ultrahigh mechanical strength offered bare 2D TMDs lateral heterostructures as a potential candidate for LIBs/SIBs applications. This work broadens the possibility of applications based on 2D TMD-based semiconductor-semiconductor and semiconductor-metal lateral heterostructures. The lateral heterostructures can give an exciting new paradigm and offer exciting opportunities for potential applications in portable electronic devices

Applied Surface Science

2D MoS2-MoSe2 and MoS2-NbS2 lateral heterostructures as anode materials for LIBs/SIBs

Ru–Bis(pyridyl)borate complex (CAT) is an efficient catalyst for ammonia borane (AB) dehydrogenation. Although the mechanistic pathway of this catalyst has been theoretically investigated previously, the gap between the experimental findings and the computational results could not be bridged thus far. In our study, using density functional theory calculations, we elucidate the mechanism of AB dehydrogenation of CAT at a variable degree of ligand hydrogenation. Our results confirm that the acetonitrile ligands get reduced in the presence of AB and remain hydrogenated. Moreover, in line with experiments, we find that AB dehydrogenation on CAT proceeds via a concerted mechanism (with the free energy energetic span between 25.4 and 32.5 kcal/mol). We find that the ligand reduction alters the electronic structure and activity of CAT and the highest activity of the catalyst is expected at the fifth degree of hydrogenation of ligands with an energetic span of 25.4 kcal/mol. Additionally, the mechanism for the removal of molecular H2 from the catalysts also alters with the degree of ligand hydrogenation. Furthermore, our results show that optimal H2 binding free energy calculations can be used as a descriptor to identify the most active sites. Finally, this work demonstrates that ligand reduction improves the activity of the catalyst. These results highlight the importance of ligand hydrogenation in probing the activity and operating mechanism of the Ru–bis(pyridyl)borate complexes for AB dehydrogenation. Further, we identify a plausible dimer structure and rationalized experimental observation that the deactivation chemistry of this catalyst is different from the Shvo’s catalyst.

Inorganic Chemistry

Unraveling the Mechanistic Details of Ru-Bis(pyridyl)borate Complex Catalyst for the Dehydrogenation of Ammonia Borane

The importance of spin state and spin coupling in gas binding selectivity in MOFs has been uncovered using periodic DFT calculations. The electron-transfer mechanism adopted by gaseous O2 leads to its strongly spin-state-dependent binding, unlike the case for N2 and H2. O2/N2-selective adsorption/desorption processes have high commercial value, and this work offers a new strategy for such selective control.The coordinatively unsaturated chromium(II)-based Cr3[(Cr4Cl)3(BTT)8]2 (Cr−BTT; BTT3−=1,3,5-benzenetristetrazolate) metal–organic framework (MOF) has been shown to exhibit exceptional selectivity towards adsorption of O2 over N2/H2. Using periodic density functional theory (DFT) calculations, we attempted to decipher the origin of this puzzling selectivity. By computing and analyzing the magnetic exchange coupling, binding energies, the partial density of states (pDOS), and adsorption isotherms for the pristine and gas-bound MOFs [(Cr4(X)4Cl)3(BTT)8]3− (X=O2, N2, and H2), we unequivocally established the role of spin states and spin coupling in controlling the gas selectivity. The computed geometries and gas adsorption isotherms are consistent with the earlier experiments. The binding of O2 to the MOF follows an electron-transfer mechanism resulting in a CrIII superoxo species (O2.−) with a very strong antiferromagnetic coupling between the two centers, whereas N2/H2 are found to weakly interact with the metal center and hence only slightly perturb the associated coupling constants. Although the gas-bound and unbound MOFs have an S=0 ground state (GS), the nature of spin the configurations and the associated magnetic exchanges are dramatically different. The binding energy and the number of oxygen molecules that can favorably bind to the Cr center were found to vary with respect to the spin state, with a significant energy margin (47.6 kJ mol−1). This study offers a hitherto unknown strategy of using spin state/spin couplings to control gas adsorption selectivity in MOFs.

Chemistry - A European Journal

The Decisive Role of Spin States and Spin Coupling in Dictating Selective O2 Adsorption in Chromium(II) Metal–Organic Frameworks**

A Theoretical Perspective to Decipher the Origin of High Hydrogen Storage Capacity in Mn(II) Metal-Organic Framework

The interatomic Coulombic decay (ICD) of the (Formula presented.) and (Formula presented.) states in neon–helium dimer is studied using highly accurate complex absorbing potential based equation-of-motion coupled cluster (CAP-EOMCC) method. The ICD decay process for the (Formula presented.) state in neon–helium dimer is closed at its equilibrium bond distance. However, the decay channel is open at large bond distance of 6.2 {\AA}. The decay channel for the double ionised (Formula presented.) state is open at 3.46 {\AA}. From our calculations, we have noticed that the decay rate of (Formula presented.) state in neon–helium dimer is four times faster compared to the (Formula presented.) state. We have also investigated how the decay rate of (Formula presented.) state in neon–helium cluster varies in the presence of different helium environment.

Molecular Physics

Interatomic Coulombic decay in Neon–Helium cluster: a complex absorbing potential based equation-of-motion coupled cluster investigation

Carbon dioxide utilization is necessary to reduce carbon footprint and also to synthesize value-added chemicals. The transition metal pincer complexes are attractive catalysts for the hydrogenation of carbon dioxide to formic acid. There is a need to understand the factors affecting the catalytic performance of these pincer complexes through a structure–activity relationship study using computational methods. It is a well-established fact that aromatic functionalities offer stability and selectivity to transition metal catalysts. However, their impact on the performance of the catalysts is lesser known in the case of metal pincer complexes. Hence, it is necessary to investigate the catalytic performance of Mn(I)NNN pincer complexes with variably activated aromatic functionalities. In this context, 15 catalysts are designed by placing different types of aromatic rings at the pincer carbons and two terminal nitrogen of Mn(I)NNN pincer complexes. A benzene moiety, placed at C2–C3 carbons of Mn(I)NNN pincer complex with identical aromatic groups at the terminal nitrogen, is found to be most efficient toward CO2 hydrogenation than the rest of the catalysts. On the other hand, when N,N-dimethyl aniline is placed at C2–C3 carbons of Mn(I)NNN pincer complexes, then the catalytic performance is significantly decreased. Thus, the present study unravels the impact of aromatic groups in Mn(I)NNN pincer complexes toward the catalytic hydrogenation of carbon dioxide. Copyright © 2021 Parmar, Avasare and Pal.

Other Publications

Fulltext

Frontiers in Chemistry

Unraveling the Effect of Aromatic Groups in Mn(I)NNN Pincer Complexes on Carbon Dioxide Activation Using Density Functional Study

A large surface-to-volume ratio is an essential feature of 2D materials used in many potential electronic applications. This work proposed that the haeckelite-structured phosphorus can be another promising alternative to the known phosphorus allotropes by DFT calculations. This allotrope can be considered a suitable anode material that may provide outstanding performance in LIBs and SIBs. Our simulations confirm that the haeckelite-structured P, composed of alternate square and octagonal rings, is thermally and mechanically stable. The phosphorus haeckelite exhibits a semiconductor with a bandgap of 2 eV and converts to a metallic phase after Li/Na adsorption, which is profoundly the basis for ideal performance of a battery. It provides a high specific capacity and a small OCV with a minimal volume expansion during lithiation/sodiation. The haeckelite-structured P exhibits much higher Li/Na adsorption properties with a small Li/Na migration barrier, which are highly essential in the charge-discharge performance of LIBs/SIBs. Based on the details mentioned above, our study would supply supportive guidelines to advance better opportunities to design and develop flexible Li/Na-ion batteries for future energy conversion and storage applications. This journal is © the Owner Societies.