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Designing an efficient and cost-effective catalyst for ammonia borane (AB) dehydrogenation remains a persistent challenge in advancing a hydrogen-based economy. Transition metal complexes, known for their C–H bond activation capabilities, have emerged as promising candidates for ABdehydrogenation. In this study, we investigated two recently synthesized C–H activation catalysts, 1(CoIV–dinitrate complex) and 2(NiIV–nitrate complex), and demonstrated their efficacy for ABdehydrogenation. Using density functional theory calculations and a detailed analysis, we elucidated the ABdehydrogenation mechanism of these complexes. Our results revealed that both complexes 1and 2can efficiently dehydrogenate ABat room temperature, although the abstraction of molecular H2from these complexes requires slightly elevated temperatures. We utilized H2binding free energy calculations to identify potentially active sites and observed that complex 2can release two equivalents of H2at a temperature slightly higher than room temperature. Furthermore, we investigated ABdehydrogenation kinetics and thermodynamics in iron (Fe)-substituted systems, complexes 3and 4. Our results showed that the strategic alteration of the central metal atom, replacing Ni in complex 2with Fe in complex 4, resulted in enhanced kinetics and thermodynamics for ABdehydrogenation in the initial cycle. These results underscore the potential of high-valent first-row transition metal complexes for facilitating ABdehydrogenation at room temperature. Additionally, our study highlights the beneficial impact of incorporating iron into such mononuclear systems, enhancing their catalytic activity.

The symmetrization map π:C2→C2is defined by π(z1,z2)=(z1+z2,z1z2).The closed symmetrized bidisc Γis the symmetrization of the closed unit bidisc D2¯, that is, Γ=π(D2¯)={(z1+z2,z1z2):|zi|≤1,i=1,2}.A pair of commuting Hilbert space operators (S, P) for which Γis a spectral set is called a Γ-contraction. Unlike the scalars in Γ, a Γ-contraction may not arise as a symmetrization of a pair of commuting contractions, even not as a symmetrization of a pair of commuting bounded operators. We characterize all Γ-contractions which are symmetrization of pairs of commuting contractions. We show by constructing a family of examples that even if a Γ-contraction (S,P)=(T1+T2,T1T2)for a pair of commuting bounded operators T1,T2, no real number less than 2 can be a bound for the set {‖T1‖,‖T2‖}in general. Then we prove that every Γ-contraction (S, P) is the restriction of a Γ-contraction (S~,P~)to a common reducing subspace of S~,P~and that (S~,P~)=(A1+A2,A1A2)for a pair of commuting operators A1,A2with max{‖A1‖,‖A2‖}≤2. We find new characterizations for the Γ-unitaries and describe the distinguished boundary of Γin a different way. We also show some interplay between the fundamental operators of two Γ-contractions (S, P) and (S1,P).

A commuting triple of Hilbert space operators (A, B, P) for which the closure of the tetrablock E, where E={(x1,x2,x3)∈C3:|x3|<1&x1=c1+x3c¯2,x2=c2+x3c¯1,c1,c2∈Cwith|c1|+|c2|<1},is a spectral set is called a tetrablock contraction or an E-contraction. To every E-contraction (A, B, P), there are unique operators F1,F2∈B(DP), which are called the fundamental operatorsof (A, B, P), satisfying A-B∗P=DPF1DP,B-A∗P=DPF2DP.An E-contraction (A, B, P) admits a canonical decomposition (A1⊕A2,B1⊕B2,P1⊕P2)into an E-unitary (A1,B1,P1)and a completely non-unitary (c.n.u.) E-contraction (A2,B2,P2). As there already exists an easily understood model for an E-unitary in the literature, it suffices to restrict attention to the c.n.u. E-contraction part. Here we construct an explicit minimal E-isometric dilation for a c.n.u. E-contraction whose fundamental operators satisfy (1.1) below (a class for which it is known that such dilation exists). As a consequence of this explicit dilation, we obtain a functional model for the same class of E-contractions. With the help of this functional model we express an E-contraction (A, B, P) as A=C1+PC2∗,B=C2+PC1∗for some operators C1,C2and this representation is operator theoretic analogue of the representation of the points in E. We also construct a different functional model, which is not necessarily commutative, for a c.n.u. E-contraction (A, B, P) when A, Bcommute with P∗. This functional model is obtained even without having an E-isometric dilation exhibited in the model. We show by an example that such a model may not be possessed by (A, B, P) if the condition that A, Bcommute with P∗, is dropped from the hypothesis. A complete unitary invariant is achieved for a c.n.u. E-contraction (A, B, P) when A, Bcommute with P∗. The fundamental operators play the central role in all these constructions. Also, we produce a new characterization for an E-unitary.

Objectives The objective of this research was to investigate the potential anti-inflammatory properties of the Cucurbita pepofruit. Given the adverse effects associated with long-term use or excessive doses of conventional anti-inflammatory medications, exploring herbal therapies as alternatives has become increasingly important.Methods Various preliminary tests and antioxidant assays, both enzymatic and non-enzymatic, were conducted on the C. pepofruit. Bioactive substances present in the fruit, including alkaloids, carbohydrates, flavonoids, tannins, amino acids, triterpenoids, and saponin glycosides, were identified through early analysis. Different extraction solvents, such as chloroform, methanol, and water, were utilized to extract samples. The methanolic extract was subjected to further testing for its in vitroanti-inflammatory characteristics. This involved evaluating their ability to stabilize RBC membranes, inhibit protein denaturation, and suppress proteinase activity using two concentrations (150 µg/ml and 300 µg/ml) of the extract.Results The methanolic extract of the C. pepofruit exhibited strong free radical scavenging activity in both DPPH and H2O2assays. Moreover, it demonstrated the dose-dependent stabilization of RBC membranes, resulting in reduced hemolysis, protein denaturation, and proteinase activity. These findings suggest potent anti-inflammatory effects of the methanolic extract.Conclusion This research study has found that the C. pepofruit methanolic extract significantly reduced inflammation. This demonstrates the promise of natural chemicals as less risky substitutes for traditional anti-inflammatory medications. Potentially safe and efficient treatments for inflammatory illnesses could be found in herbal remedies such as the C. pepofruit. Therefore, this study highlights the significance of exploring herbal remedies as a potential treatment option for inflammation-related diseases.

Molecular level understanding of liposome–gene interaction is immensely important for the research progress and technological advancement of gene delivery, which is highly significant due to a wide range of applications of gene therapy. The liposomal gene delivery method is one of the most promising techniques due to its efficacy to easily fuse with the cell membrane and its lower toxicity. In vivo gene delivery using liposomes is reported to be extremely successful. However, the success of gene delivery depends on various factors including the chemical nature of the structural unit of the liposome. To explore the regulative factor(s) for liposomal gene delivery, we systematically analyze the linker orientation effect on the gene delivery efficiency of liposomes through a density functional theory (DFT) study. Interestingly, it is observed that the liposome–gene interaction is not the regulating factor for successful gene delivery. The success depends on the gel to liquid melting temperature of the liposome.

Several toll-like receptors (TLRs) reside inside endosomes of specific immune cells—among them, aberrant activation of TLR7 and TLR9 is implicated in myriad contexts of autoimmune diseases, making them promising therapeutic targets. However, small-molecule TLR7 and TLR9 antagonists are not yet available for clinical use. We illustrate here the importance of C2, C6, and N9 substitutions in the purine scaffold for antagonism to TLR7 and TLR9 through structure–activity relationship studies using cellular reporter assays and functional studies on primary human immune cells. Further in vitroand in vivopharmacokinetic studies identified an orally bioavailable lead compound 29, with IC50values of 0.08 and 2.66 μM against TLR9 and TLR7, respectively. Isothermal titration calorimetry excluded direct TLR ligand–antagonist interactions. In vivoantagonism efficacy against mouse TLR9 and therapeutic efficacy in a preclinical murine model of psoriasis highlighted the potential of compound 29as a therapeutic candidate in relevant autoimmune contexts.

Stacking of monolayers in a layer-by-layer fashion is a convenient way of designing multilayer van der Waals (vdW) heterostructures that provide an additional range of flexibility and efficiently integrate the advantages of individual building monolayers. On the basis of first-principles DFT computation and molecular dynamics simulations, we have systematically studied the role of the graphene/blueP/MoS2van der Waals trilayer heterostructure for LIB applications. To check the stability of the trilayer heterostructure, the thermal and mechanical properties are calculated. The electronic structure of the pristine and lithiated heterostructure exhibits metallic behavior, indicating good electrical conductivity for the fast electron transport in the charge–discharge process. The Li adsorption energies on the heterostructure surfaces are much larger than those of the corresponding monolayers. The Li diffusion properties at various surfaces and interfaces of the graphene/blueP/MoS2van der Waals trilayer heterostructure are very small and extremely beneficial for battery performance. Our results expose that the trilayer heterostructure has strong potential to be used as an electrical energy storage material for Li-ion batteries, displaying strong mechanical and thermal properties, high Li binding energy, short diffusion distances, and good electronic and ionic conductivity. The current study propels a new concept of the feasibility of trilayer heterostructure materials and techniques needed to implement this innovative class of heterostructure-based materials as anodes in Li-ion batteries.

The negative ion resonance states, which are electron-molecule metastable compound states, play the most important role in free-electron controlled molecular reactions and low-energy free-electron-induced DNA damage. Their electronic structure is often only poorly described but crucial to an understanding of their reaction dynamics. One of the most important challenges to current electronic structure theory is the computation of negative ion resonance states. As a major step forward, coupled-cluster theories, which are well-known for their ability to produce the best approximate bound state electronic eigen solutions, are upgraded to offer the most accurate and effective approximations for negative ion resonance states. The existing Fock-space coupled-cluster (FSCC) and the equation-of-motion coupled-cluster (EOM-CC) approaches that compute bound states are redesigned for the direct and simultaneous determination of both the kinetic energy of the free electron at which the electron-molecule compound states are resonantly formed and the corresponding autodetachment decay rate of the electron from the metastable compound state. This Feature Article reviews the computation of negative ion resonances using the FSCC approach and, in passing, provides the highlights of the equivalent EOM-CC approach.

An extensive DFT study is carried out to explore the mechanistic pathways involved in nickel(0) catalysed functional group swapping, where the less substituted N-tosyl allylamine transforms into a more substituted N-tosyl allylamine product. Here, we demonstrated the active nickel catalyst species and transformative reaction intermediates involved in the product formation under given reaction conditions. The H-bonding and non-covalent interactions offered by a second molecule of N-tosyl allylamine coordinated to the nickel centre play a crucial role in stabilizing the key intermediates and the transition states involved in the C(2)–C(3) bond cleavage pathway. In this reversible alkenyl exchange reaction, the C(2)–C(3) bond cleavage pathway proceeds through aza-nickelacyclopentane.

Dexterity in the application of defect engineering implicates modification in the physical properties of two-dimensional (2D) transition metal dichalcogenides (TMDs) to enhance their effectiveness toward nanoelectronics applications. Subsequently, the existence of various types of defects in monolayer MoS2has been employed to inculcate and implement their significance in enhancing the Li/Na-ion storage capability of MoS2monolayers as anodes of lithium ion batteries (LIBs) and sodium ion batteries (SIBs). DFT calculations have guided us to traverse the effect of various point and antisite defects on Li/Na adsorption energy and the diffusion barrier of monolayer MoS2. Before looking into Li/Na adsorption properties of defective MoS2, the structural stability of various defects is explored with relevance to their formation energy. This also germinates the quest for the most stable defective structures that could be a reliable anode material for LIBs and SIBs. Enhanced adsorption is found for both Li/Na ions in the case of defective MoS2over that corresponding to pristine MoS2. To study the level of interaction between Li/Na and defective MoS2, electronic structure analysis has been performed. To evaluate the possible migration pathways and rate of migration of Li/Na over defective MoS2, we calculated the diffusion barrier energy through the CI-NEB method. Our study demonstrates that the formation of vacancy improves the diffusion performance of both lithium and sodium at the defective region which are prerequisites for LIBs and SIBs. Additionally, we demonstrated that the formation of vacancy could improve the specific capacity of monolayer MoS2due to a decrease of the molecular mass of defective MoS2in comparison to pristine MoS2. However, the OCV is not affected much due to enhanced adsorption. Hence, designing MoS2nanostructures with defects is a useful strategy to achieve an effective anode material for obtaining high capacity LIBs and SIBs by precisely tailoring its properties for desired applications, such as enhancing the adsorption energy, modulating the reaction pathway, and raising the specific capacity.

Density functional theory has been used for the systematic investigation of the mechanism involved in Ni(COD)2-catalyzed ipso-silylation of 2-methoxynaphthalene. The two fundamental mechanistic pathways, internal nucleophilic substitution and a nonclassical oxidative addition, have been studied. In both pathways, the first equivalent of KOtBu directly reacts with the silyl boronate (Et3SiBpin) to generate the silyl anion surrogate Et3SiK or silylborate [Et3Si-Bpin(OtBu)]K (IN3), which further reacts with Ni(COD)2to form a substrate–catalyst complex, [(η2-COD)2NiSiEt3]K. The internal nucleophilic substitution reaction pathway proceeds through η2complexation of nickel with the C(1)═C(2) bond of 2-methoxynaphthalene. Later, nickel connects to ═C(1) through σ-bond formation and coordinates with oxygen of the −OMe group. Simultaneously, the −SiEt3group approaches ═C(2) possessing −OMe followed by rearomatization which is facilitated by coordination of K+with nickel and methoxy oxygen. In a nonclassical oxidative addition, the chelation of K+with −OMe as well as −SiEt3from [(η2-COD)2NiSiEt3] is the key step which promotes the insertion of NiSiEt3to the ═C(2) carbon of 2-methoxynaphthalene. We also observed that the activation energy barrier in the non-π-extended aromatic systems is higher than that of the π-extended aromatic systems. The overall study manifests that Ni(COD)2-catalyzed ipso-silylation of 2-methoxynapthalene operates through an internal nucleophilic substitution pathway.

The influence of the ligand attachment on the activation process of carbon halogen bond on small sized aluminum nanoclusters are investigated using density functional theory. Attaching suitable ligand to metal clusters is among the widely popular techniques often used by experimentalists in order to stabilize metastable clusters. In depth theoretical investigations have shown that based on the jellium configuration of the cluster, attaching an electron withdrawing ligand can either make a cluster more reactive toward the C–I dissociation or may convert the cluster relatively inert. The alteration of the activation barriers and other associated parameters due to ligand attachment are included in this paper along with additional calculations and explanations. The study also shows that even the reaction parameters of specific magic clusters can be significantly altered via ligand attachment. The activation process of small molecules on metal clusters are of crucial importance for the development of material science and cluster chemistry. The present investigation will therefore be useful for better understanding of the properties of the ligated clusters as well as may also aid the experimentalists toward controlling the reactivity of a specific cluster as required.

Piezo1, a mechano-activated ion channel, has wide-ranging physiological and therapeutic implications, with the ongoing development of specific agonists unveiling cellular responses to mechanical stimuli. In our study, we systematically analyzed the chemical subunits in Piezo1 protein agonist Yoda1 to comprehend the structure–activity relationship and push forward next-generation agonist development. Preliminary screening assays for Piezo1 agonism were performed using the Piezo1-mCherry-transfected HEK293A cell line, keeping Yoda1 as a positive control. We introduce a novel Piezo1 agonist Yaddle1 (34, 0.40 μM), featuring a trifluoromethyl group, with further exploration through in vitro studies and density functional theory calculations, emphasizing its tetrel interactions, to act as an ambidextrous wedge between the domains of Piezo1. In contrast to the poor solubility of the established agonist Yoda1, our results showed that the kinetic solubility of Yaddle1 (26.72 ± 1.8 μM at pH 7.4) is 10-fold better than that of Yoda1 (1.22 ± 0.11 μM at pH 7.4). Yaddle1 (34) induces Ca2+influx in human CD4+T cell, suggesting its potential as a vaccine adjuvant for enhanced T cell activation.

The C(sp3)–C(sp2) bond activation reactions of 1-phenyl-2-propanone are facilitated by in situ generated Al(NO2)3as an internal oxidant and the nitrogen source. The mechanistic investigations of formation of aryl nitrile from 1-phenyl-2-propanone are performed using density functional theory calculations at the CPCM/M06-2X/6-31G(d,p) level with the conductor-like polarizable continuum model. The mechanistic pathway involves C–H bond cleavage and Beckmann fragmentation as the key steps in the formation of phenyl nitrile, and it also supports that Al(NO2)3is an active nitrite source instead of NaNO2. The C–H bond cleavage is found to be the rate-determining step with a kinetic isotope effect of 1, which is also validated by the energetic span model. The computational investigations are in good agreement with experimental results.

Development of atomic layers and their heterostructures opened new avenues in developing novel photocatalysts for enhanced light–matter interaction. Graphene–hexagonal boron nitride (G/hBN) van der Waals structures were recently predicted for interfacial exciton generation upon visible light excitation, and also, the authors have shown their van der Waals stacking-induced electrocatalytic activity. Here, an enhanced photo-electrocatalytic hydrogen evolution reaction (HER) is demonstrated upon white light illumination on samples where graphene and hBN are stacked via van der Waals interaction. The individual layers of graphene and hBN-modified electrodes have no light-induced effects along with a “poor” electrocatalytic HER activity. The origin of such light-induced activity is probed via density-functional-theory-based calculations. The catalytic activity of such heterostructures is found to be further enhanced by nanostructuring, where the coupling between individual defective graphene layers is ensured via direct carbon–carbon coupling through the Suzuki reaction. With band-engineering-induced inherent activity enhancement and nanostructuring-enabled enhanced active sites, we were able to develop a G/hBN structure that has an exceptional photo-electrocatalytic activity.

To overcome chemical limitations of camptothecin (CPT), we report design, synthesis, and validation of a quinoline-based novel class of topoisomerase 1 (Top1) inhibitors and establish that compound 28(N-(3-(1H-imidazol-1-yl)propyl)-6-(4-methoxyphenyl)-3-(1,3,4-oxadiazol-2-yl)quinolin-4-amine) exhibits the highest potency in inhibiting human Top1 activity with an IC50value of 29 ± 0.04 nM. Compound 28traps Top1–DNA cleavage complexes (Top1ccs) both in the in vitro cleavage assays and in live cells. Point mutation of Top1-N722S fails to trap compound 28-induced Top1cc because of its inability to form a hydrogen bond with compound 28. Unlike CPT, compound 28shows excellent plasma serum stability and is not a substrate of P-glycoprotein 1 (permeability glycoprotein) advancing its potential anticancer activity. Finally, we provide evidence that compound 28overcomes the chemical instability of CPT in human breast adenocarcinoma cells through generation of persistent and less reversible Top1cc-induced DNA double-strand breaks as detected by γH2AX foci immunostaining after 5 h of drug removal.

Effective modulation of electronic and optical properties by virtue of external control might unfold an extensive variety of potential applications in nanoelectronics. In this context, first-principles density functional theory calculations have been evaluated to congregate additional data about the effects of strain on the electronic properties of blue phosphorene and enactment of this with regard to potential use in lithium-ion batteries/sodium-ion batteries. The adsorption of both Li and Na over unstrained blue phosphorene is very effective with adsorption energies of −1.77 and −1.05 eV, respectively. Incredibly, the application of both compressive and tensile strains causes significant strong binding of Li/Na atoms, with Li adsorption energies of −2.03 and −2.21 eV and Na adsorption energies of −1.19 and −1.49 eV for 10% compression and 10% stretch, respectively. The diffusion of these two alkali atoms over unstrained blue phosphorene is anisotropic, with an energy barrier of 0.09 eV for Li and 0.035 eV for Na in the zigzag direction and 0.350 eV for Li and 0.207 eV for Na in the armchair direction. Mere changes are observed in the diffusion of Li on the application of strain, whereas the Na diffusion barrier energy is extremely sensitive to the applied tensile strain both in zigzag and armchair directions. The band gap of monolayer blue phosphorene is calculated by Perdew–Burke–Ernzerhof (PBE) and the more accurate Heyd–Scuseria–Ernzerhof 06 (HSE06) method. The band gap of pristine phosphorene was found to be 2.24 eV based on PBE and 2.87 eV based on the HSE06 method, which indicates that monolayer blue phosphorene is a semiconductor. However, the band gap of phosphorene is observed to be strain tunable and has a reciprocative effect with biaxial strain. The material exhibits indirect-to-direct band gap semiconductor at 10% tensile strain and semiconductor-to-semimetal transition at 10% compressive strain, whereas lithiation/sodiation induces a semiconductor-to-metal transition with unstrained phosphorene. These findings suggest that the applied strain is a robust and efficient approach to make blue phosphorene a promising material for achieving structural phase transition to meet the requirement of future electronic devices.

Amino acid–aluminum cluster complex has been shown to be a promising oxygen molecule activator and has the potential to dissociate O–O bond on the cluster surface. The study of the complex also reveals specificity of amino acid to aluminum cluster in the above complex, which can be used in the detection of amino acid. The results have been obtained by the density functional theory at the B3LYP/6-311++g(d,p) level of calculation.

Intercalation of metal ions in the van der Waals gap of layered materials forms the basis for large-scale electrochemical energy storage. In this work, by means of periodic density functional theory calculations, transition-metal dichalcogenide Mo1–xWxS2alloys have been explored as efficient materials for lithium storage. Our study reveals that lithium prefers to bind efficiently to the monolayer alloy and diffuses easily with short diffusion distances. All bare phases of alloys are semiconducting, and a semiconducting to metallic phase transition occurs after lithiation, which ensures good electrical conductivity and is crucial for electrode material. We find negligible average open-circuit voltage at different chemical stoichiometries of 0.67, 1.33, and 2. Effects of both strain and concentration on adsorption energy and diffusion barriers are calculated. The effect of strain has manifested significant rise in adsorption energy, whereas in the case of diffusion barrier, this effect is almost negligible and it remains close to the standard observed values. However, the effect of concentration has yielded very optimistic results, which are very close to the standard observed values in either case, concluding to negligible variations in both adsorption energy and diffusion barrier. All of the superior properties including high adsorption energy, low diffusion barrier, low open-circuit voltage, high specific capacity, and good electrical conductivity suggest that monolayer Mo1–xWxS2could be used as promising electrode materials in lithium-ion batteries.

Density functional theory method in combination with a continuum solvation model is used to understand the role of hydrogen bonding in the interactions of tertiary nitrogen centers of guanine and adenine with monoaqua and diaqua NAMI-A. In the case of adenine, the interaction of N3 with monoaqua NAMI-A is preferred over that of N7 and N1 whereas, N7 site is the most preferred site over N3 and N1 in the diaqua ruthenium–adenine interaction. In the monoaqua and diaqua NAMI-A–guanine interactions, the N7 site is the most preferred site over the N3 site. Here, the strength and number of H-bonds play important roles in stabilizing intermediates and transition states involved in the interaction of NAMI-A and purine bases. Atoms in molecules and Becke surface analysis confirm that the interactions between monoaqua and diaqua NAMI-A with the base pairs of GC and AT dinucleotides leads to the structural deformation in the geometry of the base pairs of dinucleotides. The diaqua NAMI-A adducts induce more disruption in the base pairs as compared to monoaqua NAMI-A adducts. which suggests that diaqua NAMI-A could be a better anticancer agent than monoaqua NAMI-A. This study can be extended to envisage the potential applications of computational studies in the development of new drugs and targeted drug delivery systems.

The present work demonstrates dissociative adsorption of molecular hydrogen on supported and unsupported aluminum clusters (Aln, n= 4–8, 13) using density functional theory based calculations. The studies reveal that the presence of a BN-doped graphene surface support reduces the dissociative adsorption barrier of the bond in molecular hydrogen on even atom clusters. In particular, supported Al6demonstrates a barrier-less dissociative adsorption toward the H2molecule. These results demonstrate the excellent potential of supported Al nanoparticles for hydrogen storage and also the potential of doped graphene systems are catalyzing supports.

Research on the investigation of new classes and new dimensionalities of materials has become considerably important in expanding the area of nanotechnology. Here, we investigate the structural, mechanical, and electronic properties of one-dimensional (1D) single-walled armchair and zigzag buckled nitrogen nanotubes by applying plane wave-based density functional theory calculations. We calculated the formation energy, structural parameters, Young’s modulus, radial Poisson’s ratio, and electronic band gap and band structures for both types of nanotubes and analyzed the change as a function of the tube radius and axial strain. The formation of armchair nanotubes is energetically favorable over that of the zigzag nanotubes. The electronic band gap increases as the size of the tube increases and decreases as the amount of strain increases. All armchair nanotubes are indirect band gap semiconductors, whereas zigzag nanotubes are direct band gap semiconductors. With a similar diameter, the Young’s modulus of a zigzag nanotube is found to be higher than that of an armchair nanotube. The electronic band gap is tuned by applying both compressive and tensile strain, which is useful in nanodevice applications. Based on the above findings, the hollow cylindrical 1D NNTs will provide a plethora of opportunities to the scientific community in the design and development of new nanostructures and enable the development of next-generation electronic devices.

The transformation of an inert structure into a catalytically active conformation has immense potential from a structural engineering point of view. In the present work, we explored methods of achieving such a transformation through a density-functional-based study. Au20is known be one of the most stable and catalytically inert gold clusters, with a well-known tetrahedral structure. We demonstrate the transformation of the inert Au20conformation into a highly active catalytic cluster through selective doping with Hf and Ge atoms. Depending on the dopant, the inert tetrahedral Au20cluster evolves into either an endohedral or a hollow-cage-like conformation. The structural changes are manifested in the catalytic properties as well, with the result that the transformed doped cages exhibit extremely low activation barriers for the environmentally important CO oxidation reaction as compared to reported inert Au20cluster. The activation barriers for CO oxidation are particularly low (<0.12 eV) when germanium is directly involved in the CO oxidation. Thus, the current work highlights the importance of engineering structural properties of metal nanoclusters with the help of heteroatom dopants for future applications in efficient catalysis.

The influence of spin on the properties of small sized transition metal doped aluminum clusters are investigated in the framework of density functional theory (DFT). Detailed analysis on minimum spin doped aluminum clusters has shown prominent indication of odd–even oscillation in various calculated properties, supporting the presence of jellium shell structures within them. However, optimized high spin ground state counterparts, on the other hand, show rather smooth trends consistent with the properties of bulk materials. Resemblance to the bulk transition metals is further reflected in the gradual declining trends of heat of adsorption of CO2molecule on cluster surface by sequentially changing the dopant atom from scandium to zinc. All the observations are also compared and found to be consistent with the earlier theoretical and experimental findings as obtained in the current literature. The similarities in the properties between atomic clusters and the bulk material is of utter importance and indeed precious considering the promising influence of the acquired information in understanding the process of evolution of nanoparticles from constituent atoms.

An ab initio design of a light emitting diode (LED) array for achieving uniform illumination is presented. An optimization technique based on evolutionary programming has been developed to facilitate the search for an optimal array in the hyperspace formed by a number of LEDs and spacing between them. Numerical results are presented for a regular and irregular array with LEDs having Lambertian and special types of light distribution.

A new approximation within the domain of EOMIP-CC method is proposed. The proposed scheme is based on the perturbative truncation of the similarity transformed effective Hamiltonian matrix. We call it the EOMIP-CCSD(2)* method, which scales as noniterative N6and its storage requirement is very less, compared to the conventional EOMIP–CCSD method. The existing EOMIP-CCSD(2) method has a tendency to overestimate the ionization potential (IP) values. On the other hand, our new strategy corrects for the problem of such an overestimation, which is evident from the excellent agreement achieved with the experimental values. Furthermore, not only the ionization potential but also geometry and IR frequencies of problematic double radicals are estimated correctly, and the results are comparable to the CCSD(T) method, obviously at lesser computational cost. The EOMIP-CCSD(2)* method works even for the core ionization and satellite IP, where the earlier EOMIP-CCSD(2) approximation dramatically fails.

Using oxygen activation and carbon monoxide oxidation as a probe, we have carried out density functional theory (DFT) calculations to investigate the effect of hydrogen atom chemisorption on the reactivity and catalytic activity of gold nanoclusters. In the present work, we particularly focus on the closed shell neutral Aun(n= 2, 4, 6, 8) gold clusters which are reported to be chemically inert and catalytically less active. The results confirm that the hydrogen atom chemisorption activates the inert clusters, thereby leading to enhanced binding and activation of the O2molecule. A significant amount of increase in the OO and decrease in the AuO bond lengths together with a pertinent red shift in the OO stretching frequencies clearly indicates the stronger binding and activation of oxygen molecule in the case of AunH clusters. Further, our results reveal that the hydrogen atom chemisorbed gold clusters are catalytically more active with low activation barriers for the CO oxidation reaction compared to the parent less active closed shell gold clusters. Thus, in short the current theoretical observation provides key inputs for enhancing the reactivity and catalytic activity of inert gold clusters through the adsorption of a small atom or a molecule.

The Fock space multireference coupled cluster (FSMRCC) method provides an efficient approach for the direct calculation of excitation energies. In intermediate Hamiltonian (IH-FSMRCC) formulation, the method is free from intruder state problems and associated convergence difficulties, even with a large model space. In this paper, we demonstrate that the IH-FSMRCC method with suitably chosen model space can be used for the accurate description of core excitation spectra of molecules, and our results are in excellent agreement with the experimental values. We have investigated the effect of choice of model space on the computed results. Unlike the equation-of-motion (EOM)-based method, the IH-FSMRCC does not require any special technique for convergence and in singles and doubles approximation gives a performance comparable to that of the standard EOMEE-CCSD method, even better in some of the cases.

N2reduction is crucial for life, and very few catalysts are currently available to carry out this process at ambient temperature and pressure. In the present work, density functional theory based calculations reveal doped aluminum clusters to be highly reactive toward molecular nitrogen and hence are prospective materials for its activation at low temperatures. Calculations on silicon and phosphorus doped aluminum clusters with 5–8 atoms demonstrate an enhanced N2activation with respect to their pristine ground state and high energy counterparts. This increased efficiency of N2activation by doped ground state Al clusters is corroborated by an increment of the NN bond length, a red shift in NN bond stretching frequency, and adsorption energy (Ead). Ab initiomolecular-dynamics simulations demonstrate consequential efficiency of doped clusters toward dinitrogen activation at finite temperature. The ability of doped clusters toward activation of molecular nitrogen is site and shape sensitive. In short, this theoretical study highlights the critical role of doping foreign impurities for future endeavors in the design of cost-effective and efficient catalysts for N2activation at ambient temperatures. This observation may spur further studies in the field of aluminum nanocatalysis by doping silicon and phosphorus atom in aluminum clusters.

We present an N5scaling modification to the standard EOMEA-CCSD method, based on the matrix partitioning technique and perturbative approximations. The method has lower computational scaling and smaller storage requirements than the standard EOMEA-CCSD method and, therefore, can be used to calculate electron affinities of large molecules and clusters. The performance and capabilities of the new method have been benchmarked with the standard EOMEA-CCSD method, for a test set of 20 small molecules, and the average absolute deviation is only 0.03 eV. The method is further used to investigate electron affinities of DNA and RNA nucleobases, and the results are in excellent agreement with the experimental values.

Doping is known to be an excellent and simple way of catalyst design. Although notable progress has been made in understanding the reactivity and catalytic activity of gas-phase and supported gold clusters, very few studies have been carried out on the doped gold clusters. In the present work, we have carried out density functional theory calculations to investigate the effect of silicon doping on the reactivity and catalytic activity of gold nanoclusters. The present work particularly focuses on the adsorption and activation of molecular oxygen on the pristine and silicon-doped gold clusters. The results confirm that the silicon-doped Au7Si cluster shows considerable binding and activation of the O2molecule in comparison to the pristine Au8cluster as reflected in the relevant geometrical parameters (O–O and Au–O bond lengths) and O–O stretching frequency. However, silicon doping has no contrasting effect on the reactivity and catalytic activity of the Au7cluster. In addition to the stronger binding and activation of the O2molecule, the doped Au7Si cluster leads to a significant reduction in the activation barrier (0.57 eV) for the environmentally important CO oxidation reaction in contrast to the catalytically inactive pristine Au8cluster (1.22 eV). Thus, our results highlight the critical role of doping foreign impurities for future endeavors in the field of gold nanocatalysis.

Conformation and electronic charge on a gold cluster are known to determine its catalytic property. However, little is known on the finite temperature behavior of various gold cluster conformations. Much less is known on the role of charge or a ligand in stabilizing a conformation at finite temperatures. In this work, we have carried out relativistic density functional theory (DFT) based molecular dynamical simulations on neutral and charged Au6clusters with an aim of understanding the stability of ground state conformations as a function of charge on the cluster. Our simulations reveal that cationic and anionic Au6clusters undergo conformational transitions at 500 K where as neutral Au6cluster retains its ground state conformation up to a temperature of 1100 K. In order to look into the factors leading to the stabilization of neutral Au6cluster (or destabilization of cationic and anionic Au6clusters), structural and electronic properties are analyzed. Factors such as charge redistribution within the atoms and composition of molecular orbitals are seen to contribute towards stronger Au–Au bonds in Au60thereby stabilizing it considerably. Following the analysis, simulations are also extended to neutral, cationic, and anionic Au6–COn(n= 1,2) complexes. In the case of CO chemisorbed Au6clusters, neutral and negatively charged ground state conformations are stable up to nearly 800 K, while the positively charged Au6ground state conformation collapses at room temperature. This work, in short demonstrates how charge or even a ligand can be used to moderate the physical properties of a gold cluster.

We present a benchmark study on the performance of the EOMIP-CCSD(2) method for computation of structure and properties of doublet radicals. The EOMIP-CCSD(2) method is a second-order approximation to the standard EOMIP-CCSD method. By retaining the black box nature of the standard EOMIP-CCSD method and adding favorable N5scaling, the EOMIP-CCSD(2) method can become the method of choice for predicting the structure and spectroscopic properties of large doublet radicals. The EOMIP-CCSD(2) method overcomes the typical problems associated with the standard single reference ab initio treatment of doublet radicals. We compare our results for geometries and harmonic vibrational frequencies with those obtained using the standard EOMIP-CCSD method, as well as unrestricted Hartree–Fock (UHF)- and restricted open-shell Hartree–Fock (ROHF)-based single-reference coupled-cluster and second order many-body perturbation theory (MBPT(2)) methods. The effect of the basis set on the quality of the results has been studied using a hierarchy of Dunning’s correlation-consistent aug-cc-pVXZ (X = D, T, Q) basis sets. Numerical results show that the EOMIP-CCSD(2) method, despite its N5scaling, gives better agreement with experimental results, compared to the UHF- and ROHF-based MBPT(2), as well as the single-reference coupled-cluster methods.

A procedure for thin lens structural design of a new class of pupil stabilized zoom systems is presented. This is facilitated by an implementation of evolutionary programming that searches a multivariate hyperspace formed by design variables, namely, powers of individual components and intercomponent separations. Two coupled components in the lens system act as the variator for the zoom system, and another component in the system acts as the compensator. A fixed axial location of the image plane is achieved by moving the coupled variator and the compensator nonlinearly, while the entrance and the exit pupils are allowed small shifts in their axial locations over the zooming range. The latter relaxation opens up the possibility for effective two-conjugate zoom systems with only two independent component movements. Illustrative examples for thin lens structures of two-conjugate zoom systems are presented.

A systematic approach for the aberration correction of zoom systems is presented. It is assumed that the powers and movements of the components of the zoom systems are known. Each component is considered as a system of thin lenses in contact. An evolutionary algorithm is developed to explore the multivariate hyperspace of design variables formed by spherical aberration, central coma, and longitudinal chromatic aberration of each component for infinite conjugate. The primary aberrations for each component at any zoom position are deduced from three central aberration coefficients of the component for infinite conjugate using conjugate shift formulas. Overall system aberrations of the zoom systems are determined by using stop shift formulas. In most of the zoom lens systems it is important to achieve stability in the primary aberrations of the system over the zoom range. This is facilitated by proper formulation of the merit function for the optimization process. Investigations have been carried out on four-component zoom lenses, and an ab initio structure of a four-component zoom lens is presented.

Transition-metal-based systems show promising binding energy for hydrogen storage but suffer from clustering problem. The effect of light transition metal (M = Sc, Ti) decoration, boron substitution on the hydrogen storage properties of MOF-5, and clustering problem of metals has been investigated using ab initio density functional theory. Our results of solid-tate calculations reveal that whereas Ti clusters strongly Sc atoms do not suffer from this problem when decorating MOF-5. Boron substitution on metal-decorated MOF-5 enhances the interaction energy of both the metals with MOF-5. Sc-decorated MOF-5 shows a hydrogen storage capacity of 5.81 wt % with calculated binding energies of 20–40 kJ/mol, which ensures the room-temperature applicability of this hydrogen storage material.

We report a theoretical investigation on the NOxcatalyzed pathways of stratospheric ozone depletion using highly accurate coupled cluster methods. These catalytic reactions represent a great challenge to state-of-the-art ab initiomethods, while their mechanisms remain unclear to both experimentalists and theoreticians. In this work, we have used the so-called “gold standard of quantum chemistry,” the CCSD(T) method, to identify the saddle points on NOx-based reaction pathways of ozone hole formation. Energies of the saddle points are calculated using the multireference variants of coupled cluster methods. The calculated activation energies and rate constants show good agreement with available experimental results. Tropospheric precursors to stratospheric NOxradicals have been identified, and their potential importance in stratospheric chemistry has been discussed. Our calculations resolve previous conflicts between ab initioand experimental results for a trans nitro peroxide intermediate, in the NOxcatalyzed pathway of ozone depletion.

Relativistic density functional theory (DFT) based molecular dynamical simulations are performed on gold clusters with 3–10 atoms (Aun, n= 3–10) with an aim of understanding their finite temperature behavior. Conformations of a cluster coexisting at different temperatures are analyzed. The simulations reveal that the finite temperature behavior of Au clusters can be classified into three regions, viz., a “solid-like” region, a “structural fluctionality” region, and a “liquid-like” state. The structural fluctionality region is when the cluster dynamically interconverts between two conformations through a metastable intermediate. For Aun, n≤ 7, where the atoms reorient continuously such that two planar conformations coexist. On the other hand, for Aun, n≥ 8, the cluster behaves as a quasi-planar liquid where the outer edge atoms of the cluster bend and relax alternatively around a central planar region. In liquid-like state the cluster is predominantly in a 3D conformation and transits through various conformations. The onset and duration of each of the above three regions are seen to be size dependent. Au6is the most stable cluster and remains in its ground state conformation (or solid-like region) up to nearly 1100 K. Au9is the least stable among the studied clusters with a liquid-like state around room temperature itself. All the clusters with the exception of Au6enter the liquid-like state at much lower temperatures as compared to that of bulk gold.

Reactivity of aluminum clusters has been found to exhibit size-sensitive variations. N2reduction is a hard process, and its dissociation on the Al surface is one of the few chemical methods available under nonhazardous conditions. In this context, we attempt to understand the adsorption behavior of N2molecules as a function of varying size and shape of Al clusters using a Density Functional Theory (DFT) based method. During the complex formation, various N2adsorption modes are examined. The results clearly demonstrate that, while the interaction energy does not vary with respect to the cluster size, shape of the cluster is highly contributive toward the chemisorption (a prerequisite for the reactivity) of the N2molecule. The underlying electronic and structural factors influencing the adsorption of N2molecules on the Al clusters are analyzed with the help of the Electron Localization Function (ELF) and Frontier Molecular Orbitals. As an illustration, the activation barrier calculations on various Al13conformations are calculated, and results confirm the experimental propositions that high-energy structures (depending upon their geometrical and electronic orientation) are more favorable for N2reduction.

In this paper, we present the new implementation of partial triples for the dipole moment of doublet radicals in Lagrangian formulation of Fock-space multireference coupled cluster (Λ-FSMRCC) response method. We have implemented a specific scheme of noniterative triples, in addition to singles and doubles schemes, which accounts for the effects appearing at least at the third order in dipole moments. The method is applied to the ground states of OH, OOH, HCOO, CN, CH, and PO radicals.

An approach for ab initio synthesis of the thin lens structure of linearly compensated zoom lenses is reported. This method uses evolutionary programming that explores the available configuration space formed by powers of the individual components, the intercomponent separations, and the relative movement parameters of the moving components. Useful thin lens structures of optically and linearly compensated zoom lens systems are obtained by suitable formulation of the merit function of optimization. This paper reports our investigations on three-component zoom lens structures. Illustrative numerical results are presented.

An effective operator approach based on the coupled cluster method is described and applied to calculate vibrational expectation values and absolute transition matrix elements. Coupled cluster linear response theory (CCLRT) is used to calculate excited states. The convergence pattern of these properties with the rank of the excitation operator is studied. The method is applied to a water molecule. Arponen-type double similarity transformation in extended coupled cluster (ECCM) framework is also used to generate an effective operator, and the convergence pattern of these properties is compared to the normal coupled cluster (NCCM) approach. It is found that the coupled cluster method provides an accurate description of these quantities for low lying vibrational excited states. The ECCM provides a significant improvement for the calculation of the transition matrix elements.

Relativistic density functional theory (DFT) based calculations have been performed on gold clusters with six to thirteen atoms (Aun; n= 6−13). The ground state geometries of these clusters as obtained from our calculations are presented and discussed. This work proposes that atoms in a ground state conformation can be classified into distinct types of reactive sites in a given geometry. Based on symmetry, susceptibility of various types of reactive sites in the ground state geometry toward an impending electrophilic and/or a nucleophilic attack has also been studied using DFT based reactivity descriptors. The studies have also been extended to high energy isomers in these cluster sizes. The reactivity of various sites as a function of cluster size and shape was thus analyzed. The study shows that as a general rule the size and shape of the cluster influences the number and position of available sites for an electrophilic and/or nucleophilic attack. This makes the reactivity patterns of these clusters highly complex. The study also highlights as to how for a cluster with seven atoms (Au7) various conformations are likely to coexist indicating that the reactivity patterns of various high energy conformations are also important while dealing with small sized Au clusters.

The influence of relativistic effects on the structure, vibrational modes, and reactivity of recently discovered tertrahedral gold clusters (Au19and Au20) are investigated using density functional methods. The intramolecular reactivity of the clusters was analyzed using density functional-based reactivity descriptors. The work shows that whereas the structural properties and vibrational modes are considerably affected by the relativistic effects, the reactivity trends based on Fukui function calculation on various atoms within this cluster remain unaffected by the absence or presence of relativistic effects. The reactivity descriptors reveal that the vertex atoms are the most reactive ones in Au20toward a nucleophilic attack. On the other hand, atoms connecting the missing vertex edge with the pyramid base along with the vertex atom are the most reactive for a nucleophilic attack in Au19. The atoms lying at the center of each face are favorable for an electrophilic attack in both cases. Interestingly, the atoms with a missing cap in Au19are highly favorable for electrophilic attack, and Au20has more sites for a favorable nucleophilic attack.

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 H2from the catalysts also alters with the degree of ligand hydrogenation. Furthermore, our results show that optimal H2binding 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.

Undesirable activation of endosomal toll-like receptors TLR7 and TLR9 present in specific immune cells in response to host-derived ligands is implicated in several autoimmune diseases and other contexts of autoreactive inflammation, making them important therapeutic targets. We report a drug development strategy identifying a new chemotype for incorporating relevant structural subunits into the basic imidazopyridine core deemed necessary for potent TLR7 and TLR9 dual antagonism. We established minimal pharmacophoric features in the core followed by hit-to-lead optimization, guided by in vitro and in vivo biological assays and ADME. A ligand–receptor binding hypothesis was proposed, and selectivity studies against TLR8 were performed. Oral absorption and efficacy of lead candidate 42were established through favorable in vitro pharmacokinetics and in vivo pharmacodynamic studies, with IC50values of 0.04 and 0.47 μM against TLR9 and TLR7, respectively. The study establishes imidazopyridine as a viable chemotype to therapeutically target TLR9 and TLR7 in relevant clinical contexts.