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A series of Mn(I) complexes Mn(L1)(CO)3Br, Mn(L2)(CO)3Br, Mn(L1)(CO)3(OAc) and Mn(L3)(CO)3Br [L1=2‐(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)‐1,8‐naphthyridine, L2=2‐(5‐tert‐butyl‐1H‐pyrazol‐3‐yl)pyridine, L3=2‐(5‐tert‐butyl‐1‐methyl‐1H‐pyrazol‐3‐yl)‐1,8‐naphthyridine] were synthesized and fully characterized. The acid‐base equilibrium between the pyrazole and the pyrazolato forms of Mn(L1)(CO)3Br was studied by 1H NMR and UV‐vis spectra. These complexes are screened as catalysts for acceptorless dehydrogenative coupling (ADC) of primary alcohols and aromatic diamines for the synthesis of benzimidazole and quinoline derivatives with the release of H2 and H2O as byproducts. The protic complex Mn(L1)(CO)3Br shows the highest catalytic activity for the synthesis of 2‐substituted benzimidazole derivatives with broad substrate scope, whereas a related complex [Mn(L3)(CO)3Br], which is devoid of the proton responsive β‐NH unit, shows significantly reduced catalytic efficiency validating the crucial role of the β‐NH functionality for the alcohol dehydrogenation reactions. Control experiments, kinetic and deuterated studies, and density functional theory (DFT) calculations reveal a synchronous hydride‐proton transfer by the metal‐ligand construct in the alcohol dehydrogenation step. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The ground state molecular frame dipole moments of alkaline earth metal monofluorides and Group ІІB‐monohydrides have been computed using two analytic methods, namely the Z‐vector technique and the linear expectation value method within the four‐component relativistic coupled cluster singles and doubles framework. We have compared our results with the experimentally measured permanent dipole moments wherever available. It is found that the Z‐vector method, which is an energy‐derivative approach predicts the molecular permanent dipole moment more accurately than the linear expectation value approach in DZ and TZ quality basis set. Further, our study shows that the high‐energy virtual spinors seem to have almost no influence on the permanent dipole moment whereas the core electron correlation slightly affects this molecular property. [ABSTRACT FROM AUTHOR]

Resonances are metastable states with finite lifetime. They play important role in physics, chemistry and biology. The theoretical calculation of resonance state is a challenging problem. In this paper we have studied the shape resonance of Be, Mg, N2 and CO. We have used correlated independent particle approximation to the Fock space multi‐reference coupled cluster singles‐doubles with third‐order triples (CAP‐CIP‐FSMRCCSD(T)) method augmented by complex absorption potential. The resonance energy and decay widths are obtained by solving a non‐Hermitian eigen‐value problem within FSMRCC framework. The effects of the lowest order triples on the resonance energy and decay are studied. [ABSTRACT FROM AUTHOR]

The development of high‐performance energy storage devices is of great interest to both the scientific fraternity and has an appalling effect in day to day life. In this regard, square octagonal‐MoS2, a reported structural analog of MoS2, has become very interesting after the successful discovery of graphene. By using plane wave‐based density functional theory, 2D haeckelite structured so‐MoS2 is explored as an appealing anode for lithium‐ion batteries/Na‐ion batteries (LIBs/SIBs). The square MoS2 provides multiple numbers of Li/Na binding sites with high adsorption energies. The computed diffusion pathways and ion migration barriers on the surfaces of the so‐MoS2 probe that the diffusion process is ultrafast in nature. Moreover, at maximum Li/Na concentration, so‐MoS2 gives rise to an electrode that manifests a larger theoretical specific capacity of 670 mAh g−1 both for Li and Na storage, equivalent to that of h‐MoS2. The lithiation/sodiation‐induced voltage range of the so‐MoS2 is quite feasible to be utilized as the anode, which is another vital factor influencing the performance of the LIBs/SIBs. All the above unique features unambiguously suggest that square octagonal MoS2 can become an efficient alternative anode material for rechargeable batteries. [ABSTRACT FROM AUTHOR]

Abstract: In this article, we investigate the performance of different approximate variants of the EOM‐CCSD method for calculation of ionization potential (IP), as compared to EOM‐CCSDT reference values. None of the lower scaling approximations to the EOM‐CCSD method give a consistent performance for valence, inner valence, and core ionization, favoring one, or the other depending on the nature of the approximation used. The parent EOMIP‐CCSD method gives superior performance for valence IP but can show large errors for inner valence and core ionization. The problem is particularly severe for core‐ionization, where even the EOMIP‐CCSDT method cannot provide quantitative accuracy. [ABSTRACT FROM AUTHOR]

Development of an efficient and durable water splitting electrocatalyst holds a great commitment for the future energy devices. The real application of oxygen evolution reaction (OER) catalysts mainly suffers from sluggish kinetics and high overpotential except for the Ir and Ru-based systems. However, the high cost and vulnerability of the Ir and Ru metals are the main hostiles to use them for marketization. Herein, a high-performance OER electrocatalyst consisting of NiCo alloy nanoparticles supported on high surface area N-doped porous graphene (NiCo/pNGr(75:25)) is reported. The importance of the doped-N for achieving the uniform dispersion-cum-effective interaction of the size controlled NiCo alloy nanoparticles has been explicitly investigated by transmission electron microscopy, X-ray diffraction, X-ray photo­electron spectroscopy, Raman, density functional theory (DFT) calculations, etc. The electrochemical analysis of NiCo/pNGr(75:25) shows an overpotential of ≈260 mV at 10 mA cm−2 with a smaller Tafel slope of ≈87 mV dec−1 and long catalytic durability. DFT calculations are done to check the interaction between the NiCo alloy nanoparticles and the defective sites of pNGr and also with the doped-N, which could be attained for maintaining long catalytic durability. Furthermore, NiCo/pNGr(75:25) is used as an OER catalyst to fabricate an electrolyzer, which works at very low potential of 1.5 V in 1 m KOH. [ABSTRACT FROM AUTHOR]

A new computational model capable of understanding the nature of interactions in signature complexes formed between the template (2,3,7,8-tetrachlorodibenzo-p dioxin (TCDD)) and the functional monomers (methacrylic acid (MAA)) using density functional theory (DFT) has been designed. The polymer precursors were optimized for geometries in polymerization media, computing the interaction energies between template molecules and functional monomers of transient pre-polymerized complexes (PPC), and structural and vibrational properties reference to theoretical infrared spectra were computed using DFT of B3LYP/6 311+G(d,p) hybrid functional method. Atom in molecule theory was used to analyze the hydrogen-bonding characteristics of PPC of MAA-TCDD. Considering the theoretical titrations conducted in a virtual solvent box, it was found that the 1:4 molar ratio was required to form the most stable PPC in a given solvent system. The electron density plots indicate strong hydrogen bonding as shown by the 2pz dominant highest occupied molecular orbital (HOMO) character that could be the preferable sites of binding for target molecule, TCDD. Considering HOMO approach, the active adsorption sites in molecularly imprinted polymer was modeled to get insight on molecular recognition property for targeted molecule, TCDD. The proposed computational protocol is simple, accurate, and novel to design the polymer and is useful to predict the properties of polymer systems than the conventional theoretical analysis of template-monomer interactions. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

We report a benchmark theoretical investigation of both vertical and adiabatic electron affinities of DNA and RNA nucleobases: adenine, guanine, cytosine, thymine, and uracil using equation of motion coupled cluster method. The vertical electron affinity (VEA) values of the first five states of the DNA and RNA nucleobases are computed. It is observed that the first electron attached state is energetically accessible in gas phase. Furthermore, an analysis of the natural orbitals exhibits that the first electron attached states of uracil and thymine are valence-bound in nature and undergo significant structural changes on attachment of an extra electron, which reflects in the deviation of the adiabatic electron affinity (AEA) than that of the vertical ones. Conversely, the first electron attached states of cytosine, adenine, and guanine are in the category of dipole-bound anions. Their structure, by and large, remain unaffected on attachment of an extra electron, which is evident from the observed small difference between the AEA and VEA values. VEA and AEA values of all the DNA and RNA nucleobases are found to be negative, which implies that the first electron attached states are not stable rather quasi bound. The results of all previous theoretical calculations are out of track and shows large deviation with respect to the experimentally measured values, whereas, our results are found to be in good agreement. Therefore, our computed values can be used as a reliable standard to calibrate new theoretical methods. © 2015 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Electronic dipole strengths (square of transition moments) and oscillator strengths are evaluated for various transitions, arising from the ground state to a few valence excited states. Parallel to two other methods of calculating the dipole strength within the Fock-space multireference coupled cluster framework, a new semi-biorthogonal approach is formulated and implemented in this article. This semi-biorthogonal approach can evaluate dipole strengths at a lower computational effort than the biorthogonal approach without compromising on the accuracy. This new method is compared and tested against the previously developed expectation value and biorthogonal approach for various molecular transitions. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The complex absorbing potential along with correlated independent particle potential (CIP) Fock space multireference coupled cluster method is used for the study of resonances. We have studied shape resonance of e−- F2, e−- N2O and e−-CO molecules. In particular, we have studied e−- F2 scattering at different bond lengths to know whether $ {\rm F}_2^- $ is bound at the equilibrium bond length of F2. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Intermolecular and intramolecular Friedel-Crafts acylation reactions of various aliphatic and aromatic esters at room temperature with the use of very simple reagents and activating groups in are described. The products were obtained in good yield (60-85 %). The detailed mechanistic pathway was studied by DFT calculations and supported by experimental evidence. [ABSTRACT FROM AUTHOR]

Conceptual density functional theory is exploited to understand the reactivity in a medium of solvents with increasing dielectric constants. Aprotic as well as protic solvents are used for this study. It is found that the global parameters, such as chemical potential and hardness, decrease from gas phase to solvent phase with increasing dielectric constant. However, it is observed that the Fukui functions of the reactive atoms increase significantly with the dielectric constants of the aprotic solvents while for the protic solvents the variation of the reactivity indices is insignificant. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 [ABSTRACT FROM AUTHOR]

The intermediate Hamiltonian state universal (Hilbert-space) coupled-cluster method is presented, using a formalism similar to that developed for the valence universal (Fock-space) approach. The method is expected to be applicable to many states not accessible by traditional multiroot multireference all-order size-extensive approaches. A pilot application to excited states of atomic beryllium shows good convergence and agreement with experiment and full CI values. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

In this article, we report the first implementation of the recently developed Fock space multireference coupled cluster (FSMRCC) response approach for magnetizabilities. The FSMRCC treats dynamic and static correlation in a very extensive manner. We report pilot application of the diamagnetizability of NO, NO2, OH, and BH2 radicals. We also report preliminary applications of the paramagnetic magnetizability of the NO radical. Standard atom-centered Gaussian basis functions have been used, and this allowed us to study the gauge dependence of the magnetizabilities. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [ABSTRACT FROM AUTHOR]

We present a benchmark study of binding energies for dioxin‐imprinted polymer complexes. A density functional theory approach was used for screening the polymerization precursors in the rational design of molecularly imprinted polymers (MIPs). Tetrachlorodibenzo‐p‐dioxin (TCDD) was taken as an imprinted molecule. The geometry optimization, natural bond orbital charge, and molecular electrostatic potential of TCDD and acrylamide (AM) were studied at the M062X level and 6‐31G(d,p) belonging to one of the hybrid density functional theories. The results of molecular electrostatic potential and natural bond orbital charge analysis were comparable. Among the studied functional monomers—AM, methacrylic acid (MAA), itaconic acid, and vinyl pyridine—AM was confirmed as the best functional monomer, because the strongest interaction (the maximum number of hydrogen bonds and the lowest binding energy) occurs between TCDD and AM. The stability property was excellent when the ratio of TCDD and AM was 1:4. The polarizable continuum model was used for solvent calculations. Computational results showed that acetonitrile plays an important role in the MIP formation, as it seems to control the size and the shape of the cavity. The atoms in molecule and Becke surface method have also been applied to understand the nature and strength of the hydrogen bonding interactions in complexes. TCDD‐AM complexes were found involving C–O···Cl and N–H···Cl hydrogen bonds. Good correlations have been established between hydrogen bond lengths versus atoms in molecule topological parameter like electron density ρ(r) and its Laplacian ▽2ρ(r) at the bond critical points. On ground of theoretical results, a series of MIPs were synthesized. The MIP prepared using TCDD as the template, the functional monomer (AM), and the cross‐linker (TRIM) in acetonitrile solvent exhibited the highest adsorption capacity for TCDD. The maximum binding capacity of TCDD on the MIP was 3.7 μg/mg. This research work can provide a theoretical reference for the fabrication and characterization of novel TCDD‐MIPs for environmental applications. This research article provides a better understanding of important interactions for the development of molecularly imprinted technology. This work will help to improve the selective detection and remediation of a particular dioxin, in environmental samples. Moreover, the theoretical simulation used in this research article is rapid and reliable for the combinatorial screening of polymer precursors in experimental‐free way to design nano‐porous polymeric material for environmental application. [ABSTRACT FROM AUTHOR]

The catalytic activity of a Ru complex 1, bearing a fused π‐conjugated imidazo[1,2–a][1,8]naphthyridine‐based mesoionic carbene (MIC) ligand, is examined for the oxidation of primary amines. Complex 1 affords nitrile or imine depending on the nature of the terminal oxidants and solvents used in the reactions. Primary amines are converted to nitriles using NaIO4 in EtOAc/H2O mixture, whereas imines are obtained under O2 balloon pressure in toluene. A variety of nitriles and imines are accessed with high yields and selectivity. A set of control experiments, reaction profiles, and kinetic studies are undertaken to disclose the mechanistic details for nitrile and imine formation. The catalytic reactions illustrate a subtle dependency on the choice of oxidants and solvents in the oxidation of primary amines. [ABSTRACT FROM AUTHOR]