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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]

Catalysis of molecular activation of small molecules through scission of strong chemical bonds is one of the major challenges faced by chemists. More specifically, activation of the strong C–H and O–H bonds of various alcohols, especially methanol, is one of the various important intermediate steps of key organic reactions. Our present work explores a suitable metal cluster catalyst towards methanol dissociation. In particular, we have examined the effect of ruthenium doping (Rh:Ru = 2:1) on the catalytic activity of Rh6 cluster towards methanol dissociation. Density functional theory-based calculations illustrate two competitive pathways for methanol dissociation, which are via O–H and C–H bond breaking. Both the pathways are found to be energetically favourable in the presence of bimetallic and mono-metallic clusters. Importantly, energy barrier for O–H bond dissociation reduces considerably in doped cluster as compared to pure Rh6 cluster and is smaller than the values reported for a number of other small metallic clusters. [ABSTRACT FROM AUTHOR]

Vinblastine (VLB), a cytotoxic alkaloid is used extensively against various cancer types and the crystal structure of its tubulin complex is already known. Multitarget affinity of vinblastine has been investigated and the nature of binding with biological receptors namely, duplex DNA and Human serum albumin (HSA) has been compared to the binding characteristics of its known complex with natural high affinity receptor tubulin using molecular docking and QM–MM calculations. VLB is found to interact with DNA as well as HSA protein, though, with weaker affinity as compared to tubulin. Analysis of various docked complexes revealed that the H-bonds and cation–pi bonds do not have significant contribution to the binding interactions and despite its large size, VLB remains in relaxed conformation and fits in the hydrophobic regions on the receptors. [ABSTRACT FROM AUTHOR]

Highlights: [•] Transesterification of DMC with glycerol was investigated using amines as catalysts. [•] Amidines like DBU and DBN were found to be the best catalysts for the reaction. [•] 98% conv. with 96% sel. to GC (TON: 9408), were obtained with DBU as a catalyst. [•] Mechanism was investigated with the help of NMR analysis and DFT calculations. [Copyright &y& Elsevier]

Invited for the cover of this issue are Sourav Pal, Gopalan Rajaraman and co‐workers at the Indian Institute of Technology Bombay, the Bhabha Atomic Research Centre and the Indian Institute of Science Education and Research. The image depicts how a mixture of atmospheric gases such as CO2, H2, N2 and O2 can be selectively separated using a Cr metal‐organic framework where spin state and spin coupling play a crucial role. Read the full text of the article at10.1002/chem.202104526. [ABSTRACT FROM AUTHOR]

Keywords: chromium superoxo; DFT calculations; gas adsorption; MOFs; spin-state calculations EN chromium superoxo DFT calculations gas adsorption MOFs spin-state calculations 1 1 1 03/31/22 20220328 NES 220328 B Using periodic DFT calculations b , we have illustrated how selective binding of O SB 2 sb over N SB 2 sb and H SB 2 sb occurs in Cr-based metal-organic frameworks (MOFs). In particular, the role of spin state and spin coupling in selective gas binding is highlighted. Chromium superoxo, DFT calculations, gas adsorption, MOFs, spin-state calculations. [Extracted from the article]

Abstract: Photoelectrochemical splitting of water with nanocrystalline Zn1−x Mn x O thin films was investigated. ZnO thin films with 1, 3, 5 and 7% at. Mn incorporation were synthesized by sol–gel method and characterized by X-Ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-ray Photoelectron spectroscopy (XPS), High Resolution Transmission Electron Microscopy (HR-TEM) and UV–Vis spectroscopy. Mn incorporation coupled with variation in sintering temperature led to significant microstructural changes, which tentatively influenced the magnitude of optical absorption and charge carrier mobility, thereby impacting the performance of such systems towards photoelectrochemical splitting of water. Electronic structure computations based on first principle density functional theory (DFT) revealed electronic states of Mn being responsible for the marginally recorded red shift in bandgap energy. Photoelectrochemical measurements using thin films of 1% at. Mn:ZnO sintered at 600 °C yielded 3 times enhanced photocurrent at zero bias due to improved optical absorption. Plausible explanations for the effect have also been offered. [Copyright &y& Elsevier]

We report a comparative single-referenceand multireference coupled-cluster investigation on the structure,potential energy surface, and IR spectroscopic properties of the transperoxo nitrate radical, one of the key intermediates in stratosphericNOXchemistry. The previous single-reference ab initiostudies predicted an unbound structure for the trans peroxo nitrateradical. However, our Fock space multireference coupled-cluster calculationconfirms a bound structure for the trans peroxo nitrate radical, inaccordance with the experimental results reported earlier. Further,the analysis of the potential energy surface in FSMRCC method indicatesa well-behaved minima, contrary to the shallow minima predicted bythe single-reference coupled-cluster method. The harmonic force fieldanalysis, of various possible isomers of peroxo nitrate also revealsthat only the trans structure leads to the experimentally observedIR peak at 1840 cm–1. The present study highlightsthe critical importance of nondynamic correlation in predicting thestructure and properties of high-energy stratospheric NOxradicals. [ABSTRACT FROM AUTHOR]

The adsorption of water molecules around a polar region (in particular around the phosphate moiety) in the phospholipid molecules is studied in this work. Phospholipid molecules with different functional groups are known to respond differently to the water molecules. Hence, we attempt to study the adsorption of water molecules around the phosphate group as a consequence of the change of functional group attached to the phosphate group, viz. phosphatidyl ethanolamine (PE), phosphatidyl choline (PC) and phosphatidyl glycerol (PG). As the latter is anionic in nature, the charge is compensated by Na+counterion. Up to seven water molecules are adsorbed around the phosphate groups in model systems mimicking phospholipid molecule. The corresponding changes in the structural and electronic aspects are analysed. The significant difference between the PE and PC model systems is the formation of clathrate-like structure in the latter. It is noticed that as the number of water molecules increases to seven, both the hydrogen atoms in the water molecule participate in hydrogen bonding. However, in the PG model system, the charge-compensating counterion prevents the water molecule to form clathrate-like structures. The adsorption sites for water molecules are validated by density functional theory-based reactivity descriptors, viz. Fukui functions in the PE model system. [ABSTRACT FROM PUBLISHER]

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]

Highlights: [•] Extended coupled cluster method is used for all calculations. [•] The energy functional is truncated up to nth perturbation order. [•] Dipole moments for all the molecules are calculated at both equilibrium and stretched geometry. [Copyright &y& Elsevier]

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]

Dipole moment calculations of SF and ClO radicals have been carried out using the recently developed partial triples correction to Fock-space multi-reference coupled cluster method. Theoretical calculation of the doublet SF and ClO radicals is useful due to their importance in atmospheric chemistry. The dipole moments of these radicals are extremely sensitive to correlation effects. A brief insight to the way the triples correction has been implemented is presented. We compare the results obtained from our analytic response treatment with that of restricted open Hartree-Fock (ROHF) calculations. Results are presented for both relaxed and non-relaxed approach in the ROHF method. Results suggest the importance of triples corrections. The effects of orbital relaxation are also analysed from the results. [Figure not available: see fulltext.] [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]

Abstract: A thorough formulation of Fock Space Brillouin–Wigner Coupled Cluster method is presented following previous developments [N.D.K. Petraco, Ľ. Horný, H.F. Schaefer, I. Hubač, J. Chem. Phys. 117 (2002) 9580]. The new method is designed to avoid the intruder states problem, and introduces the single-root solution feature which has not been considered yet within valence-universal methods. The explicit equations for the (0,1) sector of the Fock space are introduced. [Copyright &y& Elsevier]

Static polarizability and first- and second-order hyperpolarizability tensors are computed at the correlated level for a series of para-nitroaniline derivatives. The importance of including electron correlation effects in the determination of equilibrium structure and the molecular properties is investigated. A qualitative description of the substitution effects, planarity, and symmetric effect of the molecule on the molecular susceptibility is discussed. [ABSTRACT FROM AUTHOR]

Investigates the microwave irradiation of α-diazoketones that promotes Wolff rearrangement. Relevance to the nonthermal and thermal effect; Dependence on dielectric properties of the solvent used; Formation of the ring-contracted bicyclic amide.

We have recently reported a new chemotype of a potent topoisomerase I poison with compound 1 as a potential anticancer chemotherapeutic agent. During further optimization, it has been observed that compound 1 suffers from high intrinsic clearance in human liver microsomes. To overcome the metabolic instability of compound 1 , we report design and synthesis of metabolically stable Top1 poison 3. Newly identified Top1 poison 3 exhibits t 1/2 of 69.1 min in human liver microsomes in comparison to compound 1 with t 1/2 of 9.9 min. Molecular dynamic study of the newly optimized Top1 poison 3 was performed to get the insight into the stability of the binding pose in the active site. Compound 3 was able to trap DNA-Top1 cleavage complex and found to be less cytotoxic in non-cancerous cell line as compared to compound 1. Image 1 • Strategic development of potent Top1 poison with enhanced metabolic stability. • Validation of compound 3 as Top1 poison by ex vivo plasmid DNA cleavage assay. • Molecular Dynamic simulations of compound 3 in the active site. • Lead compound 3 found to be less cytotoxic in non-cancerous cell line. [ABSTRACT FROM AUTHOR]

In this article we have tried to critically analyze the factors which cause the condensed Fukui function (FF) indices [f(r)] to attain a negative value in some cases. The evaluation of condensed FF indices needs finite-difference approximation to the electronic charge densities, and the finite-difference approximation needs partitioning of the electronic charge to the constituent atoms. In a previous article [J. Chem. Phys. 110, 8236 (1999)] we have argued that the probable factors, which cause the FF indices to appear negative in some cases, may be (i) the improper charge partitioning techniques adopted to evaluate f(r); (ii) large change in the electron number (ΔN=1) when f(r) is evaluated in condensed form using the finite-difference approximation. In this article we want to focus more on the first factor. The present study shows through pictorial as well as numerical demonstrations of the charge-density difference [ρ[sub neutral](r¯)-ρ[sub cation](r¯) and ρ[sub anion](r¯)-ρ[sub neutral](r¯)] plots, how the negative condensed FF value appears with the use of improper charge partitioning and how the use of Hirshfeld partitioning can solve this problem. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

This method can be used for intermolecular as well as intramolecular Friedel-Crafts acylations, e. [ABSTRACT FROM AUTHOR]