Energy Decomposition Analysis Research Articles

Conformers of 1,4-dioxane and their hydrogen bond complexation with methanol

FTIR spectral studies has been carried out on the 1,4-dioxane (Dx), methanol (MeOH) and their binary solutions at different molar ratios. Using the experimental results in combination with the quantum chemical calculations, the conformers of Dx and their H – bonded complexes with MeOH have been analyzed. Dx exists in three different conformers, the chair, 2,5 boat and 1,4 boat with the population of 58.8 %, 21.2 % and 20.0 %, respectively, whose distinct methylene and C−O−C stretching bands have been assigned. The O−H and C−O stretching bands of MeOH existing as monomer, dimer, trimer and tetramer in liquid state have been assigned. The hydrogen bonded Dx – MeOH multimer complexes that present in each one of the binary solutions have been identified. The natural bond orbital analysis shows that the lone pair (LP)2 of oxygen involves in stronger delocalization homomolecular O−H⋯O interactions than LP(1) in all the pure MeOH multimers. This trend is retained in MeOH multimer – Dx complexes. In all the classical heteromolecular H – bond interactions also, LP(2) participates in stronger stabilization interaction while mixed trend is observed in the non-classical H – bond interactions. The energy decomposition analysis based on force field (EDA-FF) appears to fail to describe the stability of MeOH multimers as well as the Dx-MeOH hydrogen bonded complexes. But, Shubin Liu’s energy decomposition analysis (EDA-SBL) gives a correct description on the stability.

Structure and stability of the sH binary hydrate cavity and host‐guest versus guest‐guest interactions therein: A DFT approach

The intrinsic ability of clathrate hydrates to encage gaseous molecules is explored. Encapsulation ability depends on the cavity size and the type of guest gaseous species in addition to the physical parameters, temperature and pressure. Here we have reported the structure, stability and nature of interaction in dissimilar guest occupied sH hydrate cavity. Diatomic gas molecules and small polyatomic hydrocarbons are considered as guests. The irregular icosahedron (512 68 ) cavity of sH hydrate is the host. Different thermodynamic parameters for the guest molecules encapsulation were calculated using three different hybrid DFT functionals, B3LYP, M05-2X, M06, and moreover using dispersion correction (PBE0-D3). With the consideration of large H-bonded systems the 6-31G* and cc-pVTZ basis sets were used for two set of computations. To disclose the nature of interaction between the host-guest systems as well as the interaction between the guest molecules inside the host the non-covalent interaction (NCI) indices and energy decomposition analysis (EDA) were done. Impact of host-guest and guest-guest interactions are discussed.

Target State Optimized Density Functional Theory for Electronic Excited and Diabatic States.

A flexible self-consistent field method, called target state optimization (TSO), is presented for exploring electronic excited configurations and localized diabatic states. The key idea is to partition molecular orbitals into different subspaces according to the excitation or localization pattern for a target state. Because of the orbital-subspace constraint, orbitals belonging to different subspaces do not mix. Furthermore, the determinant wave function for such excited or diabatic configurations can be variationally optimized as a ground state procedure, unlike conventional ΔSCF methods, without the possibility of collapsing back to the ground state or other lower-energy configurations. The TSO method can be applied both in Hartree-Fock theory and in Kohn-Sham density functional theory (DFT). The density projection procedure and the working equations for implementing the TSO method are described along with several illustrative applications. For valence excited states of organic compounds, it was found that the computed excitation energies from TSO-DFT and time-dependent density functional theory (TD-DFT) are of similar quality with average errors of 0.5 and 0.4 eV, respectively. For core excitation, doubly excited states and charge-transfer states, the performance of TSO-DFT is clearly superior to that from conventional TD-DFT calculations. It is shown that variationally optimized charge-localized diabatic states can be defined using TSO-DFT in energy decomposition analysis to gain both qualitative and quantitative insights on intermolecular interactions. Alternatively, the variational diabatic states may be used in molecular dynamics simulation of charge transfer processes. The TSO method can also be used to define basis states in multistate density functional theory for excited states through nonorthogonal state interaction calculations. The software implementing TSO-DFT can be accessed from the authors.

Tetrel-Bond Interactions Involving Metallylenes TH2 (T = Si, Ge, Sn, Pb): Dual Binding Behavior.

The dual binding behavior of the metallylenes TH2 (T = Si, Ge, Sn, Pb) with some selected Lewis acids (T'H3F, T' = Si, Ge, Sn, Pb) and bases (N2, HCN, CO, and C6H6) has been investigated by using the high-level quantum chemical method. Two types (type-A and type-B) of tetrel-bonded complexes can be formed for TH2 due to their ambiphilic character. TH2 act as Lewis bases in type-A complexes, and they act as Lewis acids in type-B ones. CO exhibits two binding modes in the type-B complexes, one of which is TH2···CO and the other is TH2···OC. The TH2···OC complexes possess a weaker binding strength than the other type-B complexes. The TH2···OC complexes are referred to as the type-B2 complexes, and the other type-B complexes are referred to as the type-B1 complexes. The type-A complexes exhibit a relatively weak binding strength with Eint (interaction energy) values ranging from -7.11 to -15.55 kJ/mol, and the type-B complexes have a broad range of Eint values ranging from -9.45 to -98.44 kJ/mol. The Eint values of the type-A and type-B1 complexes go in the order SiH2 > GeH2 > SnH2 > PbH2. The AIM (atoms in molecules) analysis suggests that the tetrel bonds in type-A complexes are purely closed-shell interactions, and those in most type-B1 complexes have a partially covalent character. The EDA (Energy decomposition analysis) results indicate that the contribution values of the three energy terms go in the order electrostatic > dispersion > induction for the type-A and type-B2 complexes, and this order is electrostatic > induction > dispersion for the type-B1 complexes.

Molecular modeling of pyrrolo-pyrimidine based analogs as potential FGFR1 inhibitors: a scientific approach for therapeutic drugs

Fibroblast growth factor receptors 1 (FGFR1) is an emerging target for the development of anticancer drugs. Uncontrolled expression of FGFR1 is strongly associated with a number of different types of cancers. Apart from a few FGFR inhibitors, the FGFR family members have not been thoroughly studied to produce clinically effective anticancer drugs. The application of proper computational techniques may aid in understanding the mechanism of protein–ligand complex formation, which may provide a better notion for developing potent FGFR1 inhibitors. In this study, a variety of computational techniques, including 3D-QSAR, flexible docking and MD simulation followed by MMGB/PBSA, H-bonds and distance analysis, have been performed to systematically explore the binding mechanism of pyrrolo-pyrimidine derivatives against FGFR1. The 3D-QSAR model was generated to deduce the structural determinants of FGFR1 inhibition. The high q2 and r2 values for the CoMFA and CoMSIA models indicated that the created 3D-QSAR models could reliably predict the bioactivities of FGFR1 inhibitors. The computed binding free energies (MMGB/PBSA) for the selected compounds were consistent with the ranking of their experimental binding affinities against FGFR1. Furthermore, per-residue energy decomposition analysis revealed that the residues Lys514 in catalytic region, Asn568, Glu571 in solvent accessible portion and Asp641 in DFG motif exhibited a strong tendency to mediate ligand–protein interactions through the hydrogen bonding and Van Der Waals interactions. These findings may benefit researchers in gaining better knowledge of FGFR1 inhibition and may serve as a guideline for the development of novel and highly effective FGFR1 inhibitors.Communicated by Ramaswamy H. Sarma

Unravelling the Mechanism and Governing Factors in Lewis Acid and Non-Covalent Diels-Alder Catalysis: Different Perspectives.

In the current literature, many non-covalent interaction (NCI) donors have been proposed that can potentially catalyze Diels-Alder (DA) reactions. In this study, a detailed analysis of the governing factors in Lewis acid and non-covalent catalysis of three types of DA reactions was carried out, for which we selected a set of hydrogen-, halogen-, chalcogen-, and pnictogen-bond donors. We found that the more stable the NCI donor-dienophile complex, the larger the reduction in DA activation energy. We also showed that for active catalysts, a significant part of the stabilization was caused by orbital interactions, though electrostatic interactions dominated. Traditionally, DA catalysis was attributed to improved orbital interactions between the diene and dienophile. Recently, Vermeeren and co-workers applied the activation strain model (ASM) of reactivity, combined with the Ziegler-Rauk-type energy decomposition analysis (EDA), to catalyzed DA reactions in which energy contributions for the uncatalyzed and catalyzed reaction were compared at a consistent geometry. They concluded that reduced Pauli repulsion energy, and not enhanced orbital interaction energy, was responsible for the catalysis. However, when the degree of asynchronicity of the reaction is altered to a large extent, as is the case for our studied hetero-DA reactions, the ASM should be employed with caution. We therefore proposed an alternative and complementary approach, in which EDA values for the catalyzed transition-state geometry, with the catalyst present or deleted, can be compared one to one, directly measuring the effect of the catalyst on the physical factors governing the DA catalysis. We discovered that enhanced orbital interactions are often the main driver for catalysis and that Pauli repulsion plays a varying role.

Exploring the solvation of water molecules around radioactive elements in nuclear waste water treatment

Abstract Nuclear waste water contains many actinides which coordinate with water molecules to form complexes. The hydration of water molecules with varying coordination numbers and modes makes it interesting and intriguing in understanding the extraction process of these radioactive ions. In order to separate these complexes from the nuclear waste water, many organic ligands are being used. However, prior knowledge on the nature of electronic environment of these hydration patterns will help us to understand the extraction mechanism. Therefore, a series of complexes such as [Np(H2O)9]4+, [Cm(H2O)9]3+, [Am(H2O)9]3+, [Pu(H2O)9]4+, [Pu(H2O)9]3+, [U(H2O)9]3+, [NpO2(H2O)5]+, [UO2(H2O)5]2+ and [PuO2(H2O)5]2+ have been calculated by means of relativistic DFT. Bond length analysis and energy decomposition analysis are executed with the intention to comprehend the bonding situation of these complexes. To account for the stabilizing interactions amid the radioactive ion and the water molecules, a detailed QTAIM investigation is done. It is seen that the metals having higher oxidation state readily complex with water molecules. Energy decomposition analysis throws light on the significant orbital interactions in the [M(H2O)9] n complexes, whereas in the metal oxide complexes significant contribution is resulted from electrostatic interactions. In summary, this investigation brings out the nuances of coordination modes of solvation in nuclear waste water which will help us to explore and design novel extraction techniques in near future.

Insights Into Resveratrol as an Inhibitor Against Aβ1-42 Peptide Aggregation: A Molecular Dynamics Simulation Study

Background: Resveratrol (RSV), a polyphenolic compound, is reported to have anti-aggregation properties against Amyloid-beta peptides. It is, therefore, significant to understand the mechanism of inhibition of Aβ1-42 peptide aggregation by the RSV at the molecular level. We have used Molecular docking along with Molecular dynamics (MD) simulation techniques to address the role of RSV in the inhibition of Aβ1-42 pep-tide aggregation. Objective: To understand the role of Resveratrol on the Aβ1-42 peptide aggregation. Method: In this computational study, we have docked the RSV to Aβ1-42 peptide using Molecular Docking software and then performed MD simulation for the Aβ1-42 peptide monomer Aβ1-42 peptide-RSV complex using the AMBER force field. From the analysis of MD trajectories, we obtained salient structural features and determined the Binding Free Energy(BFE) and Per-residue Energy Decomposition Analysis (PRED) using MM-PBSA/GBSA method. Results: The secondary structure and the conformational analysis obtained from MD trajectories show that the binding of RSV with the Aβ1-42 peptide monomer causes an increase in the helical content in the structure of the Aβ1-42 peptide. The BFE and PRED results show a high binding affinity (GBtotal=-11.07 kcal mol-1; PBtotal= -1.82 kcal mol-1) of RSV with Aβ1-42 peptide. Also, we found the RSV to interact with cru-cial residues (Asp 23 and Lys 28) of the Aβ1-42 peptide. These residues play a signif-icant role in facilitating the formation of toxic amyloid oligomers and amyloid fibrils. The salt bridge interaction between these residues D23–K28 was found to be destabi-lized in the Aβ1-42 peptide when it is complexed with RSV. Conclusion: In summary, it can be concluded that Resveratrol greatly aids the preven-tion of Aβ1-42 peptide aggregation. Therefore, it can be considered a possible drug candidate for therapeutic strategies for Alzheimer’s disease.

Intermolecular interactions of cytosine DNA nucleoside base with Gallic acid and its Methylgallate and Ethylgallate derivatives

Abstract3,4,5‐trihydroxybenzlic acid (gallic acid) and its derivatives exist mostly as secondary metabolites of the phenol family found in plants. Herein, the interaction of gallic acid (GA), methylgallic acid (MGA), ethylgallic acid (EGA) with cytosine (the most reactive part of DNA) has been studied in detail using first principle density functional theory (DFT). Several interaction configurations between the gallic acid and selected derivatives have been investigated using DFT at the M06‐2X/6‐31+G(d,p) theoretical method, topological analysis based on quantum theory of atoms‐in‐molecule (QTAIM), and the noncovalent interaction (NCI) which aid in the understanding of interactions between studied compounds. The results obtained from the interaction energy and energy decomposition analysis (EDA) show that methylgallate (GA) has the largest interaction energy with cytosine, along with the strongest H‐bond interaction and is best suited for drug design due to its lowest value of stabilization energy at the interaction site 1.Similarly, weak interactions were observed between EGA and cytosine of DNA between −0.02 to 0.01 a.u with a sparing trace of H bond with the aid of non‐covalent interaction (NCI). The reactivity of the studied compound depicts GA to be the most reactive. Although gallic acid competes favorably, this study, however, revealed the great potential of its derivatives: EGA and MGA having great potential for drug design. Their applications are vast and mostly hinged on antioxidant properties, especially in the pharmaceutical industry and, hence, form the basis of an effective class of phytomedicines.

H – Bond interactions in water multimers and water multimers – Pyridine complexes: Natural bond orbital and reduced density gradient isosurface analyses

Natural bond orbital and reduced density gradient isosurface analyses have been carried out on the water multimers of order n=1-9 and twenty-five complexes of Pyridine (Py) with water multimers of order n=1-5 optimized using density functional theory at B3LYP level of theory with the basis set 6–311++G(d,p). Among the twenty-five Py-Water structures, the seventeen configurations whose interaction energies are above 49 kJ/mol have been taken into consideration. The interaction (binding) energy values indicate that i) the 1(Py): 5 (water)/1:2 complexes are found to be the most/least stable networks and ii) the stability increases with increase in the number of water molecules in water multimers only. The occupancy and second order perturbation energy profiles suggest that O-H⋯N hydrogen bond is stronger than O-H⋯O, C-H⋯O and O-H⋯π hydrogen bonds. The non-classical hydrogen bonds and π→σ∗ interactions are also characterized by the green coloured regions in the reduced density gradient isosurfaces. The Shubin Liu energy decomposition (EDA-SBL) analysis shows that the water multimers and the Py-Water complexes are dominantly stabilized by the attractive electrostatic interactions. Of the two functionals, the B3LYP and ωB97XD, the latter which is meant for accounting the dispersion interaction disallows the O-H⋯π interaction between Py and water molecules and therefore, the former appears to give correct description on Py-Water interactions.

Stable Crystalline Nanohoop Radical and Its Self-Association Promoted by van der Waals Interactions.

A stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X-ray crystallographic analysis reveals that OR3 forms a unique head-to-tail dimer that further aggregates into a one-dimensional chain in the solid state. Variable-temperature NMR and concentration-dependent absorption measurements indicate that the π-dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self-association process, in contrast with other olympicenyl derivatives that favor π-dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one-electron chemical oxidation. This study offers a new molecular design to modulate the self-association of organic radicals for overcoming the spin-Peierls transition, and to prepare novel nanohoop compounds with spin-related properties.

Stable Crystalline Nanohoop Radical and Its Self‐Association Promoted by van der Waals Interactions

AbstractA stable nanohoop radical (OR3) combining the structures of cycloparaphenylene and an olympicenyl radical is synthesized and isolated in the crystalline state. X‐ray crystallographic analysis reveals that OR3 forms a unique head‐to‐tail dimer that further aggregates into a one‐dimensional chain in the solid state. Variable‐temperature NMR and concentration‐dependent absorption measurements indicate that the π‐dimer is not formed in solution. An energy decomposition analysis indicates that van der Waals interactions are the driving force for the self‐association process, in contrast with other olympicenyl derivatives that favor π‐dimerization. The physical properties in solution phase have been studied, and the stable cationic species obtained by one‐electron chemical oxidation. This study offers a new molecular design to modulate the self‐association of organic radicals for overcoming the spin‐Peierls transition, and to prepare novel nanohoop compounds with spin‐related properties.

Radical Pairing Interactions and Donor-Acceptor Interactions in Cyclobis(paraquat-p-phenylene) Inclusion Complexes.

Understanding molecular interactions in mechanically interlocked molecules (MIMs) is challenging because they can be either donor-acceptor interactions or radical pairing interactions, depending on the charge states and multiplicities in the different components of the MIMs. In this work, for the first time, the interactions between cyclobis(paraquat-p-phenylene) (abbreviated as CBPQTn+ (n = 0-4)) and a series of recognition units (RUs) were investigated using the energy decomposition analysis approach (EDA). These RUs include bipyridinium radical cation (BIPY•+), naphthalene-1,8:4,5-bis(dicarboximide) radical anion (NDI•-), their oxidized states (BIPY2+ and NDI), neutral electron-rich tetrathiafulvalene (TTF) and neutral bis-dithiazolyl radical (BTA•). The results of generalized Kohn-Sham energy decomposition analysis (GKS-EDA) reveal that for the CBPQTn+···RU interactions, correlation/dispersion terms always have large contributions, while electrostatic and desolvation terms are sensitive to the variation in charge states in CBPQTn+ and RU. For all the CBPQTn+···RU interactions, desolvation terms always tend to overcome the repulsive electrostatic interactions between the CBPQT cation and RU cation. Electrostatic interaction is important when RU has the negative charge. Moreover, the different physical origins of donor-acceptor interactions and radical pairing interactions are compared and discussed. Compared to donor-acceptor interactions, in radical pairing interactions, the polarization term is always small, while the correlation/dispersion term is important. With regard to donor-acceptor interactions, in some cases, polarization terms could be quite large due to the electron transfer between the CBPQT ring and RU, which responds to the large geometrical relaxation of the whole systems.

Rotational dive into the water clusters on a simple sugar substrate

Most biomolecular activity takes place in aqueous environments, and it is strongly influenced by the surrounding water molecules. The hydrogen bond networks that these water molecules form are likewise influenced by their interactions with the solutes, and thus, it is crucial to understand this reciprocal process. Glycoaldehyde (Gly), often considered the smallest sugar, represents a good template to explore the steps of solvation and determine how the organic molecule shapes the structure and hydrogen bond network of the solvating water cluster. Here, we report a broadband rotational spectroscopy study on the stepwise hydration of Gly with up to six water molecules. We reveal the preferred hydrogen bond networks formed when water molecules start to form three-dimensional (3D) topologies around an organic molecule. We observe that water self-aggregation prevails even in these early stages of microsolvation. These hydrogen bond networks manifest themselves through the insertion of the small sugar monomer in the pure water cluster in a way in which the oxygen atom framework and hydrogen bond network resemble those of the smallest three-dimensional pure water clusters. Of particular interest is the identification, in both the pentahydrate and hexahydrate, of the previously observed prismatic pure water heptamer motif. Our results show that some specific hydrogen bond networks are preferred and survive the solvation of a small organic molecule, mimicking those of pure water clusters. A many-body decomposition analysis of the interaction energy is also performed to rationalize the strength of a particular hydrogen bond, and it successfully confirms the experimental findings.

Molecular insights on PS-PLA1 lipase activity of human ABHD16B

The human alpha beta hydrolase domain (ABHD) proteins are ubiquitous and regulate the cellular lipids' anabolic and catabolic processes. The structural aspects for specific biochemical function of many ABHD proteins related to physiological disorders and its link to pathological conditions remain unknown. Here putative human ABHD16B protein was overexpressed in Saccharomyces cerevisiae for its biological activity. In-vitro enzymatic assay of the recombinant ABHD16B protein with fluorescently tagged glycerophospholipids revealed that the PLA1 activity is observed with phosphatidylserine (PS). In addition, it efficiently hydrolyzed monoacylglycerol over triacylglycerols. Further, molecular dynamic simulations and per residue binding free energy decomposition analysis revealed that the origin of PS-specific PLA1 activity of ABHD16B is due to the electrostatic interaction of the PS head group with K8, R319, and E178, which led to having the hydrogen bond interaction of sn-1 acyl chain ester to the catalytic site residues. Site-directed mutagenesis of the 245GXSXG249 motif of ABHD16B reduced the maximal lipase activity of PS and MAG. In summary, these results revealed that ABHD16B plays a vital role in PS selectivity that in turn, controls the specific subcellular pools of 2-LPS metabolism in the tissues at low pH.

Origins of Regioselectivity in CuH-Catalyzed Hydrofunctionalization of Alkenes.

Factors controlling the regioselectivity in alkene hydrocupration were computationally investigated using energy decomposition analysis. The results demonstrate that the Markovnikov-selective hydrocupration with electronically activated mono-substituted olefins is mostly affected by the destabilizing Pauli repulsion, which is due to the electron delocalization effect. The anti-Markovnikov-selective hydrocupration with 1,1-dialkyl-substituted terminal olefins is dominated by the repulsive electrostatic interactions, which is because of the unequal π electron distribution caused by the induction effect of alkyl substituents.

The combination of polyphenols and phospholipids as an efficient platform for delivery of natural products

Although nature is a rich source of potential drugs and drug leads, the widespread application of natural products (NPs) is limited due to their poor absorption when administered orally. A strategy of using phytosome has emerged as a promising technique to increase the bioavailability of NPs. Here, a comprehensive computational investigation is performed to explore the nature of interactions in the formation of phytosomes between phosphatidylcholine (PC) and a series of polyphenols (PP), including epigallocatechin-3-gallate (Eg), luteolin (Lu), quercetin (Qu), and resveratrol (Re). Our quantum mechanical calculation revealed that the intermolecular hydrogen bonds (HBs) of phosphate and glycerol parts of PC with the polyphenol compounds are the main driving force in the formation of phytosomes. The strongest HB (with energy HB = − 108.718 kJ/mol) is formed between the Eg molecule and PC. This hydrogen bond results from the flexible structure of the drug which along with several van der Waals (vdW) interactions, makes Eg-PC the most stable complex (adsorption energy = − 164.93 kJ/mol). Energy decomposition analysis confirms that the electrostatic interactions (hydrogen bond and dipole-diploe interactions) have a major contribution to the stabilization of the studied complexes. The obtained results from the molecular dynamics simulation revealed that the formation of phytosomes varies depending on the type of polyphenol. It is found that the intermolecular hydrogen bonds between PP and PC are a key factor in the behavior of the PP-PC complex in the self-aggregation of phytosome. In Eg-PC, Lu-PC, and Qu-PC systems, the formation of strong hydrogen bonds (HBCP < 0 and ∇2ρBCP > 0) between PP and PC protects the PP-PC complexes from degradation. The steered molecular dynamics simulation results have a good agreement with experimental data and confirm that the phytosome platform facilitates the penetration of PP compounds into the membrane cells.

Force Decomposition Analysis: A Method to Decompose Intermolecular Forces into Physically Relevant Component Contributions

Computational quantum chemistry can be more than just numerical experiments when methods are specifically adapted to investigate chemical concepts. One important example is the development of energy decomposition analysis (EDA) to reveal the physical driving forces behind intermolecular interactions. In EDA, typically the interaction energy from a good-quality density functional theory (DFT) calculation is decomposed into multiple additive components that unveil permanent and induced electrostatics, Pauli repulsion, dispersion, and charge-transfer contributions to noncovalent interactions. Herein, we formulate, implement, and investigate decomposing the forces associated with intermolecular interactions into the same components. The resulting force decomposition analysis (FDA) is potentially useful as a complement to the EDA to understand chemistry, while also providing far more information than an EDA for data analysis purposes such as training physics-based force fields. We apply the FDA based on absolutely localized molecular orbitals (ALMOs) to analyze interactions of water with sodium and chloride ions as well as in the water dimer. We also analyze the forces responsible for geometric changes in carbon dioxide upon adsorption onto (and activation by) gold and silver anions. We also investigate how the force components of an EDA-based force field for water clusters, namely MB-UCB, compare to those from force decomposition analysis.

Understanding the Coordination Chemistry of AmIII/CmIII in the DOTA Cavity: Insights from Energetics and Electronic Structure Theory.

The minor actinides Am/Cm show multiple possibilities for coordination, providing great opportunities for their extraction and adsorption separation. Herein, we report complexation in an aqueous medium of AmIII/CmIII in the DOTA (H4DOTA = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid) cavity with axial ligands (OH-, F-, and H2O), based on the energetics and electronic structure properties using density functional theory (DFT). The formation and substitution reactions of OH--capped complexes are more likely to occur due to their enhanced hydration Gibbs free energies, followed by F-, and then H2O. Both the longer An-ODOTA bond lengths and the larger bite angle (∠O-An-O) in the OH--capped complexes reflect the enhanced coordination provided by the axial ligand, slightly less so for F-. Energy decomposition analysis based on the electronic structure supports the preference for OH--capped complexes with a near-perfect balance between attractive and repulsive contributions toward the interaction. Furthermore, molecular orbital analysis revealed that the frontier molecular orbitals of Am and Cm complexes are substantially different; that is, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) compositions of the Am complexes are all contributed by 5f, while the HOMO and LUMO compositions of the Cm complexes are derived from 5f and 6d, respectively. Finally, the metal-exchange reactions demonstrate competitive complexation of DOTA toward AmIII over CmIII for the OH--capped system. These results imply the importance of coordination chemistry in actinide chemistry in general and specifically in AmIII/CmIII solution chemistry.

The interaction between nucleotide bases and nano carbon: The dimension dominates

Understanding the interaction mechanism between nucleotide bases (NBs) and carbon substrate nanomaterials is a major scientific issue in the field of bioactive molecule identification, which is of great significance for digital diagnosis, gene sequencing, drug development and human health. In this work, the adsorption behavior of five typical NBs molecules A, T, C, G and U on the surface of the widely used carbon-based nanomaterials such as fullerene, carbon nanotubes and graphene, was investigated comprehensively from first-principle views. The adsorption of NBs molecules over the surface of these nano-carbon materials was described rationally and intuitively from both quantitative and qualitative perspectives. The adsorption ability and binding intensity of NBs over the three carbon-based substrates showed obvious population differences. This was mainly because the three carbon materials had different periodic dimensions and thus the electron motion and surface electron properties were affected by the low-dimensional quantum confined effect. The above results indicated the dimension-dominant effect of the interaction between NBs and nano-carbon materials. Through energy decomposition analysis, it was further quantitatively explained that the interaction was dominated by dispersion force. By means of reduced density gradient, Van der Waals surface penetration and charge differential density analysis, the regions, types and intensities of the adsorption for NBs over carbon substrates were intuitively described. This work was important to understand the dimension-dominant effect of the interaction between NBs and carbon nanomaterials.