Synthesis, characterization, and density functional theory investigation of (CH6N3)2[NpO2Cl3] and Rb[NpO2Cl2(H2O)] chain structures

The actinyl tetrachloro complex [An(V/VI)O2Cl4]2-/3- tends to form discrete molecular units in both solution and solid state materials, but related aquachloro complexes have been observed as both discrete coordination compounds and 1-D chain topologies. Subtle differences in the inner sphere coordination significantly influence the formation of structural topologies in the actinyl chloride system, but the exact reasoning for these variations has not been delineated. In the current study, we present the synthesis, structural characterization, and vibrational analysis of two 1-D neptunyl(V) chain compounds: (CH6N3)2[NpO2Cl3] (Np-Gua) and Rb[NpO2Cl2(H2O)] (Np-Rb). Bonding and non-covalent interactions (NCIs) in the systems were evaluated using periodic Density Functional Theory (DFT) to link these properties to related phases. We observed ∼6.5% and ∼3.9% weakening of NpO bonds in Np-Gua and Np-Rb compared to the reference Cs3[NpO2Cl4]. NCI analysis distinguished specific assembly modes, where Np-Gua was connected via hydrogen bonding (N-H⋯Cleq and N-H⋯Oyl) and Np-Rb contained both cation interactions (Rb+⋯Oyl and Rb+⋯Cleq) and hydrogen bonding (Oeq-H⋯Oyl) networks. Thermodynamically viable formation pathways for both compounds were explored using DFT methodology. The [NpO2Cl4](aq)3- and [NpO2Cl3(H2O)](aq)2- substructures were identified as precursors to Np-Gua and [NpO2Cl3(H2O)](aq)2- and [NpO2Cl2(H2O)2](aq)- were isolated as the primary building units of Np-Rb. Finally, we utilized DFT to analyze the vibrational modes for Np-Gua and Np-Rb, where we found evidence of the NpO bond weakening within the Np(V) chain structures compared to [NpO2Cl4]3-.

Three-Dimensional Noncovalent Interaction Network within [NpO2Cl4]2- Coordination Compounds: Influence on Thermochemical and Vibrational Properties

Noncovalent interactions (NCIs) can influence the stability and chemical properties of pentavalent and hexavalent actinyl (AnO2+/2+) compounds. In this work, the impact of NCIs (actinyl-hydrogen and actinyl-cation interactions) on the enthalpy of formation (ΔHf) and vibrational features was evaluated using Np(VI) tetrachloro compounds as the model system. We calculated the ΔHf values of these solid-state compounds through density functional theory+ thermodynamics (DFT+ T) and validated the results against experimental ΔHf values obtained through isothermal acid calorimetry. Three structural descriptors were evaluated to develop predictors for ΔHf, finding a strong link between ΔHf and hydrogen bond energy (EHtotal) for neptunyl-hydrogen interactions and total electrostatic attraction energy (Eelectrostatictotal) for neptunyl-cation interactions. Finally, we used Raman spectroscopy together with bond order analysis to probe Np=O bond perturbation due to NCIs. Our results showed a strong correlation between the degree of NCIs by axial oxygen and red-shifting of Np=O symmetrical stretch (ν1) wavenumbers and quantitatively demonstrated that NCIs can weaken the Np=O bond. These properties were then compared to those of related U(VI) and Np(V) phases to evaluate the effects of subtle differences in the NCIs and overall properties. In general, the outcomes of our study demonstrated the role of NCIs in stabilizing actinyl solid materials, which consequently governs their thermochemical behaviors and vibrational signatures.

Synthesis, Characterization, and Density Functional Theory Investigation of the Solid-State [UO2Cl4(H2O)]2- Complex

A significant number of solid-state [UO2Cl4]2- coordination compounds have been synthesized and structurally characterized. Yet, despite their purposive relative abundance in aqueous solutions, characterization of aquachlorouranium(VI) complexes remain rare. In the current study, a solid-state uranyl aqua chloro complex ((C4H12N2)2[UO2Cl4(H2O)]Cl2) was synthesized using piperazinium as a charge-balancing ligand, and the structure was determined using single-crystal X-ray diffraction. Using periodic density functional theory, the electronic structure of the [UO2Cl4(H2O)]2- complex was compared to [UO2Cl4]2- to uncover the strengthening of the U═O bond in [UO2Cl4(H2O)]2-. Changes in the strength of the U═O bond were validated further with Raman and IR spectroscopy, where uranyl symmetrical (ν1) and asymmetrical (ν3) stretches were blue-shifted compared to the reference [UO2Cl4]2- complex. Furthermore, the formation energy of the solid-state (C4H12N2)2[UO2Cl4(H2O)]Cl2 complex was calculated to be -287.60 ± 1.75 kJ mol-1 using isothermal acid calorimetry. The demonstrated higher stability relative to the related [UO2Cl4]2- complex was related to the relative stoichiometry of the counterions.

Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non-Covalent Interactions in a Uranyl Tetrahalide Model System

Together with the synthesis and experimental characterization of 14 hybrid materials containing [UO2 X4 ]2- (X=Cl- and Br- ) and organic cations, we report on novel methods for determining correlation trends in their formation enthalpy (ΔHf ) and observed vibrational signatures. ΔHf values were analyzed through isothermal acid calorimetry and a Density Functional Theory+Thermodynamics (DFT+T) approach with results showing good agreement between theory and experiment. Three factors (packing efficiency, cation protonation enthalpy, and hydrogen bonding energy [E H , norm total ${{E}_{H,{\rm { norm}}}^{{\rm { total}}}}$ ]) were assessed as descriptors for trends in ΔHf . Results demonstrated a strong correlation betweenE H , norm total ${E_{{\rm{H}},{\rm{norm}}}^{{\rm{total}}} }$ and ΔHf , highlighting the importance of hydrogen bonding networks in determining the relative stability of solid-state hybrid materials. Lastly, we investigate how hydrogen bonding networks affect the vibrational characteristics of uranyl solid-state materials using experimental Raman and IR spectroscopy and theoretical bond orders and find that hydrogen bonding can red-shift U≡O stretching modes. Overall, the tightly integrated experimental and theoretical studies presented here bridge the trends in macroscopic thermodynamic energies and spectroscopic features with molecular-level details of the geometry and electronic structure. This modeling framework forms a basis for exploring 3D hydrogen bonding as a tunable design feature in the pursuit of supramolecular materials by rational design.

Influencing Bonding Interactions of the Neptunyl (V, VI) Cations with Electron-Donating and -Withdrawing Groups

Neptunium makes up the largest percentage of minor actinides found in spent nuclear fuel, yet separations of this element have proven difficult due to its rich redox chemistry. Developing new reprocessing techniques should rely on understanding how to control the Np oxidation state and its interactions with different ligands. Designing new ligands for separations requires understanding how to properly tune a system toward a desired trait through functionalization. Emerging technologies for minor actinide separations focus on ligands containing carboxylate or pyridine functional groups, which are desirable due to their high degree of functionalization. Here, we use DFT calculations to study the interactions of carboxylate and polypyridine ligands with the neptunyl cation [Np(V/VI)O2]+/2+. A systematic study is performed by varying the electronic properties of the carboxylate and polypyridine ligands through the inclusion of different electron-withdrawing and electron-donating R groups. We focus on how these groups can affect geometric properties, electronic structure, and bonding characterization as a function of the metal oxidation state and ligand character and discuss how these factors can play a role in neptunium ligand design principles.

Periodic Density Functional Theory Calculations of Uranyl Tetrachloride Compounds Engaged in Uranyl-Cation and Uranyl-Hydrogen Interactions: Electronic Structure, Vibrational, and Thermodynamic Analyses

Solid-state uranyl hybrid structures are often formed through unique intermolecular interactions occurring between a molecular uranyl anion and a charge-balancing cation. In this work, solid-state structures of the uranyl tetrachloride anion engaged in uranyl-cation and uranyl-hydrogen interactions were studied using density functional theory (DFT). As most first-principles methods used for systems of this type focus primarily on the molecular structure, we present an extensive benchmarking study to understand the methods needed to accurately model the geometric properties of these systems. From there, the electronic and vibrational structures of the compounds were investigated through projected density of states and phonon analysis and compared to the experiment. Lastly, we present a DFT + thermodynamics approach to calculate the formation enthalpies (ΔHf) of these systems to directly relate to experimental values. Through this methodology, we were able to accurately capture trends observed in experimental results and saw good quantitative agreement in predicted ΔHf compared to the value calculated through referencing each structure to its standard state. Overall, results from this work will be used for future combined experimental and computational studies on both uranyl and neptunyl hybrid structures to delineate how varying intermolecular interaction strengths relates to the overall values of ΔHf.

Investigations of the Cobalt Hexamine Uranyl Carbonate System: Understanding the Influence of Charge and Hydrogen Bonding on the Modification of Vibrational Modes in Uranyl Compounds

Hydrogen bonding networks within hexavalent uranium materials are complex and may influence the overall physical and chemical properties of the system. This is particularly true if hydrogen bonding takes places between the donor and the oxo group associated with the uranyl cation (UO₂²⁺). In the current study, we evaluate the impact of charge-assisted hydrogen bonding on the vibrational modes of the uranyl cation using uranyl tricarbonate [UO₂(CO₃)₃]^4- interactions with [Co(NH₃)₆]³⁺ as the model system. Herein, we report the synthesis and structural characterization of five novel compounds, [Co(NH₃)₆]Cl(CO₃) (Co_Cl_CO₃), [Co(NH₃)₆]₄[UO₂(CO₃)₃]₃(H₂O)_11.67 (Co4U3), [Co(NH₃)₆]₃[UO₂(CO₃)₃]₂Cl (H₂O)_7.5 (Co3U2_Cl), [Co(NH₃)₆]₂[UO₂(CO₃)₃]Cl₂ (Co2U_Cl), and [Co(NH₃)₆]₂[UO₂(CO₃)₃]CO₃ (Co2U_CO₃), which contain differences in the crystalline packing and extended hydrogen bonding networks. We show that these slight changes in the supramolecular assembly and hydrogen bonding networks result in the modification of modes as observed by infrared and Raman spectroscopy. We use density functional theory calculations to assign the vibrational modes and provide an understanding about how uranyl bond perturbation and changes in hydrogen bonding interactions can impact the resulting spectroscopic signals.

Binding of polar and hydrophobic molecules at the LiCoO2 (001)-water interface: force field development and molecular dynamics simulations

A classical model in the framework of the INTERFACE force field has been developed for treating the LiCoO₂ (LCO) (001)/water interface. In comparison to ab initio molecular dynamics (MD) simulations based on density functional theory, MD simulations using the classical model lead to generally reliable descriptions of interfacial properties, such as the density distribution of water molecules. Water molecules in close contact with the LCO surface form a strongly adsorbed layer, which leads to a free energy barrier for the adsorption of polar or charged molecules to the LCO surface. Moreover, due to the strong hydrogen bonding interactions with the LCO surface, the first water layer forms an interface that exhibits hydrophobic characters, leading to favorable adsorption of non-polar molecules to the interface. Therefore, despite its highly polar nature, the LCO (001) surface binds not only polar/charged but also non-polar solutes. As an application, the model is used to analyze the adsorption of reduced nicotinamide adenine dinucleotide (NADH) and its molecular components to the LCO (001) surface in water. The results suggest that recently observed redox activity of NADH at the LCO/water interface was due to the co-operativity between the ribose component, which drives binding to the LCO surface, and the nicotinamide moiety, which undergoes oxidation.

Use of vibrational spectroscopy to identify the formation of neptunyl-neptunyl interactions: A paired Density Functional Theory and Raman spectroscopy study

Abstract: Actinyl-Actinyl interactions (AAIs) occur in pentavalent actinide systems, particularly for Np(V), and lead to complex vibrational signals that are challenging to analyze and interpret. Previous studies have focused on...

Adsorption of small organic acids and polyphenols on hematite surfaces: Density Functional Theory + thermodynamics analysis

HYPOTHESIS

The interactions of organic molecules with mineral surfaces are influenced by several factors such as adsorbate speciation, surface atomic and electronic structure, and environmental conditions. When coupled with thermodynamic techniques, energetics from atomistic modeling can provide a molecular-level picture of which factors determine reactivity. This is paramount for evaluating the chemical processes which control the fate of these species in the environment.

EXPERIMENTS

Inner-sphere adsorption of oxalate and pyrocatechol on (001), (110), and (012) α-Fe₂O₃ surfaces was modeled using Density Functional Theory (DFT). Unique bidentate binding modes were sampled along each facet to study how different adsorbate and surface factors govern site preference. Adsorption energetics were then calculated using a DFT + thermodynamics approach which combines DFT energies with tabulated data and Nernst-based corrective terms to incorporate different experimental parameters.

FINDINGS

Instead of a universal trend, each facet displays a unique factor that dominates site preference based on either strain (001), functional groups (110), or topography (012). Adsorption energies predict favorable inner-sphere adsorption for both molecules but opposite energetic trends with varying pH. Additionally, vibrational analysis was conducted for each system and compared to experimental IR data. The work presented here provides an effective, computational methodology to study numerous adsorption processes occurring at the surface-aqueous interface.

Formation of Nanoscale [Ge4 O16 Al48 (OH)108 (H2 O)24 ]20+ from Condensation of ϵ-GeAl12 8+ Keggin Polycations*

Keggin-type polyaluminum cations belong to a unique class of compounds with their large positive charge, hydroxo bridges, and divergent isomerization/oligomerization. Previous reports indicated that oligomerization of this species can only occur through one isomer (δ), but herein we report the isolation of largest Keggin-type cluster that occurs through self-condensation of four ϵ-isomers ϵ-GeAl₁₂ ⁸⁺ to form [Ge₄ O₁₆ Al₄₈ (OH)₁₀₈ (H₂ O)₂₄ ]²⁰⁺ cluster (Ge₄ Al₄₈ ). The cluster was crystallized and structurally characterized by single-crystal X-ray diffraction (SCXRD) and the elemental composition was confirmed by ICP-MS and SEM-EDS. Additional dynamic light scattering experiments confirms the presence of the Ge₄ Al₄₈ in thermally aged solutions. DFT calculations reveal that a single atom Ge substitution in tetrahedral site of ϵ-isomer is the key for the formation of Ge₄ Al₄₈ because it activates deprotonation at key surface sites that control the self-condensation process.

Density functional theory and thermodynamics analysis of MAl12 Keggin substitution reactions: Insights into ion incorporation and experimental confirmation

Polyaluminum cations, such as the MAl₁₂ Keggin, undergo atomic substitutions at the heteroatom site (M), where nanoclusters with M = Al³⁺, Ga³⁺, and Ge⁴⁺ have been experimentally studied. The identity of the heteroatom M has been shown to influence the structural and electronic properties of the nanocluster and the kinetics of ligand exchange reactions. To date, only three ε-analogs have been identified, and there is a need for a predictive model to guide experiment to the discovery of new MAl₁₂ species. Here, we present a density functional theory (DFT) and thermodynamics approach to predicting favorable heteroatom substitution reactions, alongside structural analyses on hypothetical ε-MAl₁₂ nanocluster models. We delineate trends in energetics and geometry based on heteroatom cation properties, finding that Al³⁺-O bond lengths are related to heteroatom cation size, charge, and speciation. Our analyses also enable us to identify potentially isolable new ε-MAl₁₂ species, such as FeAl₁₂ ⁷⁺. Based upon these results, we evaluated the Al³⁺/Zn²⁺/Cr³⁺ system and determined that substitution of Cr³⁺ is unfavorable in the heteroatom site but is preferred for Zn²⁺, in agreement with the experimental structures. Complimentary experimental studies resulted in the isolation of Cr³⁺-substituted δ-Keggin species where Cr³⁺ substitution occurs only in the octahedral positions. The isolated structures Na[AlO₄Al_9.6Cr_2.4(OH)₂₄(H₂O)₁₂](2,6-NDS)₄(H₂O)₂₂ (δ-Cr_nAl_13-n-1) and Na[AlO₄Al_9.5Cr_2.5(OH)₂₄(H₂O)₁₂](2,7-NDS)₄(H₂O)_18.5 (δ-Cr_nAl_13-n-2) are the first pieces of evidence of mixed Al³⁺/Cr³⁺ Keggin-type nanoclusters that prefer substitution at the octahedral sites. The δ-Cr_nAl_13-n-2 structure also exhibits a unique placement of the bound Na⁺ cation, which may indicate that Cr³⁺ substitution can alter the surface reactivity of Keggin-type species.

Density Functional Theory and Thermodynamics Modeling of Inner-Sphere Oxyanion Adsorption on the Hydroxylated α-Al2O3(001) Surface

The inner-sphere adsorption of AsO₄^3-, PO₄^3-, and SO₄^2- on the hydroxylated α-Al₂O₃(001) surface was modeled with the goal of adapting a density functional theory (DFT) and thermodynamics framework for calculating the adsorption energetics. While DFT is a reliable method for predicting various properties of solids, including crystalline materials comprised of hundreds (or even thousands) of atoms, adding aqueous energetics in heterogeneous systems poses steep challenges for modeling. This is in part due to the fact that environmentally relevant variations in the chemical surroundings cannot be captured atomistically without increasing the system size beyond tractable limits. The DFT + thermodynamics approach to this conundrum is to combine the DFT total energies with tabulated solution-phase data and Nernst-based corrective terms to incorporate experimentally tunable parameters such as concentration. Central to this approach is the design of thermodynamic cycles that partition the overall reaction (here, inner-sphere adsorption proceeding via ligand exchange) into elementary steps that can either be fully calculated or for which tabulated data are available. The ultimate goal is to develop a modeling framework that takes into account subtleties of the substrate (such as adsorption-induced surface relaxation) and energies associated with the aqueous environment such that adsorption at mineral-water interfaces can be reliably predicted, allowing for comparisons in the denticity and protonation state of the adsorbing species. Based on the relative amount of experimental information available for AsO₄^3-, PO₄^3-, and SO₄^2- adsorbates and the well-characterized hydroxylated α-Al₂O₃(001) surface, these systems are chosen to form a basis for assessing the model predictions. We discuss how the DFT + thermodynamics results are in line with the experimental information about the oxyanion sorption behavior. Additionally, a vibrational analysis was conducted for the charge-neutral oxyanion complexes and is compared to the available experimental findings to discern the inner-sphere adsorption phonon modes. The DFT + thermodynamics framework used here is readily extendable to other chemical processes at solid-liquid interfaces, and we discuss future directions for modeling surface processes at mineral-water and environmental interfaces.

Ga3+ Incorporation into Al13 Keggin Polyoxometalates and the Formation of δ-(GaAl12)7+ and (Ga2.5Al28.5)19+ Polycations

Keggin-type polyaluminum species (ε-Al₁₃, δ-Al₁₃, Al₂₆, Al₃₀, Al₃₂) can form upon partial hydrolysis of Al³⁺-bearing solutions and are important species for water purification and contaminant transport. While the structural features for the major Al³⁺ polyaluminum species have been delineated, much less is known regarding heteroatom substitution and resultant structures other than the previously identified ε-GaAl₁₂⁷⁺ and ε-GeAl₁₂⁸⁺ cations. Single-atom substitution within polyaluminum species can change the surface reactivity within water treatment scenarios; thus, it is important to understand heteroatom incorporation within this system. The present work describes the synthesis and characterization of two novel Ga³⁺-substituted Keggin-type polyaluminum species. Na[GaO₄Al₁₂(OH)₂₄(H₂O)₁₂](2,6-NDS)₄(H₂O)_20.5 (δ-GaAl₁₂) and [Ga₂O₈Al_28.5Ga_0.5(OH)₅₈(H₂O)₂₇(SO₄)₂](SO₄)₄Cl₇(H₂O)_8.5 (Ga_2.5Al_28.5) were crystallized from a thermally aged, partially hydrolyzed Ga³⁺/Al³⁺ solution. Structural refinement from single-crystal X-ray diffraction indicated fully occupied Ga³⁺ within tetrahedral site(s) of both isolated species. Partial substitution was observed for octahedral sites for the larger Ga_2.5Al_28.5 cluster. The chemical compositions of both clusters were confirmed by inductively coupled plasma mass spectrometry (ICP-MS). Density functional theory (DFT) calculations corroborated the structural refinement, with the energetics of Ga³⁺ substitution suggesting preferential substitution within tetrahedral sites for both species. Additional theoretical work suggests that the rotated trimer in δ-GaAl₁₂ is highly reactive, which can serve as the driving force in the formation of the Ga_2.5Al_28.5 cluster.

Impacts of hydrogen bonding interactions with Np(v/vi)O2Cl4 complexes: vibrational spectroscopy, redox behavior, and computational analysis

The neptunyl (Np(v)O₂⁺/Np(vi)O₂²⁺) cation is the dominant form of ²³⁷Np in acidic aqueous solutions and the stability of the Np(v) and Np(vi) species is driven by the specific chemical constituents present in the system. Hydrogen bonding with the oxo group may impact the stability of these species, but there is limited understanding of how these intermolecular interactions influence the behavior of both solution and solid-state species. In the current study, we systematically evaluate the interactions between the neptunyl tetrachloride species and hydrogen donors in coordination complexes and in the related aqueous solutions. Both Np(v) compounds (N₂C₄H₁₂)₂[Np(v)O₂Cl₄]Cl (Np(V)pipz) and (NOC₄H₁₀)₃[Np(v)O₂Cl₄] (Np(V)morph) exhibit directional hydrogen bonding to the neptunyl oxo group while Np(vi) compounds (NC₅H₆)₂[Np(vi)O₂Cl₄] (Np(VI)pyr) and (NOC₄H₁₀)₄[Np(vi)O₂Cl₄]·2Cl (Np(VI)morph) assemble via halogen interactions. The Raman spectra of the solid-state phases indicate the activation of vibrational bands when there is asymmetry of the neptunyl bond, while these spectral features are not observed within the related solution phase spectra. Density functional theory calculations of the Np(V)pipz system suggest that activation of the ν₃ asymmetric stretch and other combination modes lead to additional complexity within the solid-state spectra. Electrochemical analyses of complexes in the solution phases are consistent with the results of the crystallization experiments as the voltammetric potentials of Np(v)/Np(vi) complexes in the presence of protonated heterocycles differ from the potentials of pure Np(v) and may correlate with the hydrogen bonding interactions.

Actinyl-cation interactions: experimental and theoretical assessment of [Np(vi)O2Cl4]2- and [U(vi)O2Cl4]2- systems

The interaction of the actinyl (AnO₂²⁺) oxo group with low-valent cations influences the chemical and physical properties of hexavalent actinides, but the impact of these intermolecular interactions on the actinyl bond and their occurrence in solution and solid state phases remain unclear. In this study, we explore the coordination of alkali cations (Li⁺, Na⁺, K⁺) with the [NpO₂Cl₄]^2- coordination complexes using single-crystal X-ray diffraction, Raman spectroscopy, and density functional theory (DFT) calculations and compare to the related uranyl system. Three solid-state coordination compounds ([Li(12-crown-4)]₂[NpO₂Cl₄] (LiNp), [Na(18-crown-6)H₂O]₂[NpO₂Cl₄] (NaNp), and [K(18-crown-6)]₂[NpO₂Cl₄] (KNp) have been synthesized and characterized using single-crystal X-ray diffraction and Raman spectroscopy. Only Li⁺ cations interact with the neptunyl oxo in the solid-state compounds and this results in a red-shift of the NpO₂²⁺ symmetric stretch (ν₁). Raman spectra of Np(vi) solutions containing lower Li⁺ concentrations display a single peak at ∼854 cm^-1 and increasing the amount of Li⁺ results in the ingrowth of a second band at 807 cm^-1. DFT calculations and vibrational analysis indicate the lower frequency vibrational band is the result of interactions between the Li⁺ cation and the neptunyl oxo. Comparison to the related uranyl system shows similar interactions occur in the solid state, but subtle differences in the actinyl-cation modes in solution phase.

Molecular Surface Functionalization of Carbon Materials via Radical-Induced Grafting of Terminal Alkenes

Formation of functional monolayers on surfaces of carbon materials is inherently difficult because of the high bond strength of carbon and because common pathways such as SN2 mechanisms cannot take place at surfaces of solid materials. Here, we show that the radical initiators can selectively abstract H atoms from H-terminated carbon surfaces, initiating regioselective grafting of terminal alkenes to surfaces of diamond, glassy carbon, and polymeric carbon dots. Nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS) demonstrate formation of self-terminating organic monolayers linked via the terminal C atom of 1-alkenes. Density functional theory (DFT) calculations suggest that this selectivity is at least partially thermodynamic in origin, as significantly less energy is needed to abstract H atoms from carbon surfaces as compared to typical aliphatic compounds. The regioselectivity favoring binding to the terminal C atom of the reactant alkenes arises from steric hindrance encountered in bond formation at the adjacent carbon atom. Our results demonstrate that carbon surface radical chemistry yields a versatile, selective, and scalable approach to monolayer formation on H-terminated carbon surfaces and provide mechanistic insights into the surface selectivity and regioselectivity of molecular grafting.

DFT Computed Dielectric Response and THz Spectra of Organic Co-Crystals and Their Constituent Components

Terahertz (THz) spectroscopy has been put forth as a non-contact, analytical probe to characterize the intermolecular interactions of biologically active molecules, specifically as a way to understand, better develop, and use active pharmaceutical ingredients. An obstacle towards fully utilizing this technique as a probe is the need to couple features in the THz regions to specific vibrational modes and interactions. One solution is to use density functional theory (DFT) methods to assign specific vibrational modes to signals in the THz region, coupling atomistic insights to spectral features. Here, we use open source planewave DFT packages that employ ultrasoft pseudopotentials to assess the infrared (IR) response of organic compounds and complex co-crystal formulations in the solid state, with and without dispersion corrections. We compare our DFT computed lattice parameters and vibrational modes to experiment and comment on how to improve the agreement between theory and modeling to allow for THz spectroscopy to be used as an analytical probe in complex biologically relevant systems.

Prospective Risk Factor Analysis for the Development of Post-operative Urinary Retention Following Ambulatory General Surgery

Aims

Post-operative urinary retention (POUR) is a common cause of unplanned admission following day-case surgery and has negative effects on both patient and surgical institution. We aimed to prospectively evaluate potential risk factors for the development of POUR following day-case general surgical procedures.

Methods

Over a 24-week period, consecutive adult patients undergoing elective day-case general surgery at a single institution were prospectively recruited. Data regarding urinary symptoms, comorbidities, drug history, surgery and perioperative anaesthetic drug use were collected. The primary outcome was the incidence of POUR, defined as an impairment of bladder voiding requiring either urethral catheterisation, unplanned overnight admission or both. Potential risk factors for the development of POUR were analysed by logistic regression.

Results

A total of 458 patients met the inclusion criteria during the study period, and data were collected on 382 (83%) patients (74.3% male). Sixteen patients (4.2%) experienced POUR. Unadjusted analysis demonstrated three significant risk factors for the development of POUR: age ≥ 56 years (OR 7.77 [2.18–27.78], p = 0.002), laparoscopic surgery (OR 3.37 [1.03–12.10], p = 0.044) and glycopyrrolate administration (OR 5.56 [2.00–15.46], p = 0.001). Male sex and lower urinary tract symptoms were not significant factors. Multivariate analysis combining type of surgery, age and glycopyrrolate use revealed that only age ≥ 56 years (OR 8.14 [2.18–30.32], p = 0.0018) and glycopyrrolate administration (OR 3.48 [1.08–11.24], p = 0.0370) were independently associated with POUR.

Conclusions

Patients aged at least 56 years and/or requiring glycopyrrolate—often administered during laparoscopic procedures—are at increased risk of POUR following ambulatory general surgery.

Electronic supplementary material

The online version of this article (10.1007/s00268-018-4697-4) contains supplementary material, which is available to authorized users.

Impact of Phosphate Adsorption on Complex Cobalt Oxide Nanoparticle Dispersibility in Aqueous Media

A commonly overlooked and largely unknown aspect of assessing the environmental and biological safety of engineered nanomaterials is their transformation in aqueous systems. Complex metal oxides are an important class of materials for catalysis, energy storage, and water purification. However, the potential impact of nano complex metal oxides on the environment upon improper disposal is not well understood. We present a comprehensive analysis of the interaction of an environmentally relevant oxyanion, phosphate, with a complex metal oxide nanomaterial, lithium cobalt oxide. Our results show that adsorption of phosphate to the surface of these materials drastically impacts their surface charge, rendering them more stable in aqueous systems. The adsorbed phosphate remains on the surface over significant periods of time, suggesting that desorption is not kinetically favored. The implications of this interaction may be increased dispersibility and bioavailability of these materials in environmental water systems.

Dissolution of Complex Metal Oxides from First-Principles and Thermodynamics: Cation Removal from the (001) Surface of Li(Ni1/3Mn1/3Co1/3)O2

The rapid increase in use of Li-ion batteries in portable electronics has created a pressing need to understand the environmental impact and long-term fate of electonic waste (e-waste) products such as heavy and/or reactive metals. The type of e-waste that we focus on here are the complex metal oxide nanomaterials that compose Li-ion battery cathodes. While in operation the complex metal oxides are in a hermetically sealed container. However, at the end of life, improper disposal can cause structural transformations such as dissolution and metal leaching, resulting in a significant exposure risk to the surrounding environment. The transformations that occur between operational to environmental settings gives rise to a stark knowledge gap between macroscopic design and molecular-level behavior. In this study we use theory and modeling to describe and explain previously published experimental data for cation release from Li(Ni_1/3Mn_1/3Co_1/3)O₂ (NMC) nanoparticles in an aqueous environment ( Chem. Mater. 2016 (28) 1092-1100). To better understand the transformations that may occur when this material is exposed to the environment, we compute the free energy of surface dissolution, Δ G, from the complex metal oxide NMC for a range of surface terminations and pH.

Analysis of the conformational properties of amine ligands at the gold/water interface with QM, MM and QM/MM simulations

We describe a strategy of integrating quantum mechanical (QM), hybrid quantum mechanical/molecular mechanical (QM/MM) and MM simulations to analyze the physical properties of a solid/water interface.

Using density functional theory to study shape-reactivity relationships in Keggin Al-nanoclusters

Keggin-based aluminum nanoclusters have been shown to be efficient sorbents for the removal of arsenic from water. Obtaining a molecular-level understanding of the adsorption processes associated with these molecules is of fundamental importance, and could pave the way for rational design strategies for water treatment. Due to their size and the availability of experimental crystal structures, Al nanoclusters are computationally tractable at the density functional theory (DFT) level. Here, we compare the reactivity of three aluminum polycations: [Al13O4(OH)24(H2O)12](7+) (Al13), [Al30O8(OH)56(H2O)26](18+) (Al30), and [Al32O8(OH)60(H2O)30](20+) (Al32). We use DFT calculations to determine reactivity as a function of particle topography, using sulfate and chloride as adsorption probes. Our comparative modeling of outer-sphere adsorption of Cl(-) and SO4(2-) on Al13, Al30, and A132 supports that the unique "hourglass" shape characteristic to Al30 gives rise to relatively strong adsorption in the molecular beltway, as well as a wide range of reaction energies as a function of particle topography.

Sustainable Nanotechnology: Opportunities and Challenges for Theoretical/Computational Studies

For assistance in the design of the next generation of nanomaterials that are functional and have minimal health and safety concerns, it is imperative to establish causality, rather than correlations, in how properties of nanomaterials determine biological and environmental outcomes. Due to the vast design space available and the complexity of nano/bio interfaces, theoretical and computational studies are expected to play a major role in this context. In this minireview, we highlight opportunities and pressing challenges for theoretical and computational chemistry approaches to explore the relevant physicochemical processes that span broad length and time scales. We focus discussions on a bottom-up framework that relies on the determination of correct intermolecular forces, accurate molecular dynamics, and coarse-graining procedures to systematically bridge the scales, although top-down approaches are also effective at providing insights for many problems such as the effects of nanoparticles on biological membranes.

Isolation and characterization of the [Ga2Al18O8(OH)36(H2O)12](8+) cluster: cationic variations on the Wells-Dawson topology

The structural chemistry of Group 13 polyoxometalates lags far behind related negatively charged transition metal species and limits the development of advanced materials. A novel heterometallic cluster [Ga2Al18O8(OH)36(H2O)12](8+) (Ga2Al18) has been isolated using a supramolecular approach and structurally characterized using single-crystal X-ray diffraction. Ga2Al18 represents the Wells-Dawson structure polycations and variations in the structural topology may be related to the initial stabilization of the Keggin isomer. DFT calculations on the related ε-Keggins (GaAl12 and Al13), Ga2Al18, and theoretical Al2Al18 clusters reveal similar features of electronic structure, suggesting additional heteroatom substitution in other isostructural clusters should be possible.

Risk stratification by the Appendicitis Inflammatory Response score to guide decision-making in patients with suspected appendicitis

BACKGROUND

Current management of suspected appendicitis is hampered by the overadmission of patients with non-specific abdominal pain and a significant negative exploration rate. The potential benefits of risk stratification by the Appendicitis Inflammatory Response (AIR) score to guide clinical decision-making were assessed.

METHODS

During this 50-week prospective observational study at one institution, the AIR score was calculated for all patients admitted with suspected appendicitis. Appendicitis was diagnosed by histological examination, and patients were classified as having non-appendicitis pain if histological findings were negative or surgery was not performed. The diagnostic performance of the AIR score and the potential for risk stratification to reduce admissions, optimize imaging and prevent unnecessary explorations were quantified.

RESULTS

A total of 464 patients were included, of whom 210 (63·3 per cent) with non-appendicitis pain were correctly classified as low risk. However, 13 low-risk patients had appendicitis. Low-risk patients accounted for 48·1 per cent of admissions (223 of 464), 57 per cent of negative explorations (48 of 84) and 50·7 per cent of imaging requests (149 of 294). An AIR score of 5 or more (intermediate and high risk) had high sensitivity for all severities of appendicitis (90 per cent) and also for advanced appendicitis (98 per cent). An AIR score of 9 or more (high risk) was very specific (97 per cent) for appendicitis, and the majority of patients with appendicitis in the high-risk group (21 of 30, 70 per cent) had perforation or gangrene. Ultrasound imaging could not exclude appendicitis in low-risk patients (negative likelihood ratio (LR) 1·0) but could rule-in the diagnosis in intermediate-risk patients (positive LR 10·2). CT could exclude appendicitis in low-risk patients (negative LR 0·0) and rule-in appendicitis in the intermediate group (positive LR 10·9).

CONCLUSION

Risk stratification of patients with suspected appendicitis by the AIR score could guide decision-making to reduce admissions, optimize utility of diagnostic imaging and prevent negative explorations.

The use of Lean and Six Sigma methodologies in surgery: a systematic review

BACKGROUND

Lean and Six Sigma are improvement methodologies developed in the manufacturing industry and have been applied to healthcare settings since the 1990 s. They use a systematic and reproducible approach to provide Quality Improvement (QI), with a flexible process that can be applied to a range of outcomes across different patient groups. This review assesses the literature with regard to the use and utility of Lean and Six Sigma methodologies in surgery.

METHODS

MEDLINE, Embase, PsycINFO, Allied and Complementary Medicine Database, British Nursing Index, Cumulative Index to Nursing and Allied Health Literature, Health Business Elite and the Health Management Information Consortium were searched in January 2014. Experimental studies were included if they assessed the use of Lean or Six Sigma on the ability to improve specified outcomes in surgical patients.

RESULTS

Of the 124 studies returned, 23 were suitable for inclusion with 11 assessing Lean, 6 Six Sigma and 6 Lean Six Sigma. The broad range of outcomes can be collated into six common aims: to optimise outpatient efficiency, to improve operating theatre efficiency, to decrease operative complications, to reduce ward-based harms, to reduce mortality and to limit unnecessary cost and length of stay. The majority of studies (88%) demonstrate improvement; however high levels of systematic bias and imprecision were evident.

CONCLUSION

Lean and Six Sigma QI methodologies have the potential to produce clinically significant improvement for surgical patients. However there is a need to conduct high-quality studies with low risk of systematic bias in order to further understand their role.

Short communication: an in vitro assessment of the antibacterial activity of plant-derived oils

Nonantibiotic treatments for mastitis are needed in organic dairy herds. Plant-derived oils may be useful but efficacy and potential mechanisms of action of such oils in mastitis therapy have not been well documented. The objective of the current study was to evaluate the antibacterial activity of the plant-derived oil components of Phyto-Mast (Bovinity Health LLC, Narvon, PA), an herbal intramammary product, against 3 mastitis-causing pathogens: Staphylococcus aureus, Staphylococcus chromogenes, and Streptococcus uberis. Plant-derived oils evaluated were Thymus vulgaris (thyme), Gaultheria procumbens (wintergreen), Glycyrrhiza uralensis (Chinese licorice), Angelica sinensis, and Angelica dahurica. Broth dilution testing according to standard protocol was performed using ultrapasteurized whole milk instead of broth. Controls included milk only (negative control), milk + bacteria (positive control), and milk + bacteria + penicillin-streptomycin (antibiotic control, at 1 and 5% concentrations). Essential oil of thyme was tested by itself and not in combination with other oils because of its known antibacterial activity. The other plant-derived oils were tested alone and in combination for a total of 15 treatments, each replicated 3 times and tested at 0.5, 1, 2, and 4% to simulate concentrations potentially achievable in the milk within the pre-dry-off udder quarter. Thyme oil at concentrations ≥2% completely inhibited bacterial growth in all replications. Other plant-derived oils tested alone or in various combinations were not consistently antibacterial and did not show typical dose-response effects. Only thyme essential oil had consistent antibacterial activity against the 3 mastitis-causing organisms tested in vitro. Further evaluation of physiological effects of thyme oil in various preparations on mammary tissue is recommended to determine potential suitability for mastitis therapy.

Contaminant adsorption on nanoscale particles: structural and theoretical characterization of Cu2+ bonding on the surface of Keggin-type polyaluminum (Al30) molecular species

The adsorption of contaminants onto metal oxide surfaces with nanoscale Keggin-type structural topologies has been well established, but identification of the reactive sites and the exact binding mechanism are lacking. Polyaluminum species can be utilized as geochemical model compounds to provide molecular level details of the adsorption process. An Al30 Keggin-type species with two surface-bound Cu(2+) cations (Cu2Al30-S) has been crystallized in the presence of disulfonate anions and structurally characterized by single-crystal X-ray diffraction. Density functional theory (DFT) calculations of aqueous molecular analogues for Cu2Al30-S suggest that the reactivity of Al30 toward Cu(2+) and SO4(2-) shows opposite trends in preferred adsorption site as a function of particle topology, with anions preferring the beltway and cations preferring the caps. The bonding competition was modeled using two stepwise reaction schemes that consider Cu2Al30-S formation through initial Cu(2+) or SO4(2-) adsorption. The associated DFT energetics and charge density analyses suggest that strong electrostatic interactions between SO4(2-) and the beltway of Al30 play a vital role in governing where Cu(2+) binds. The calculated electrostatic potential of Al30 provides a theoretical interpretation of the topology-dependent reactivity that is consistent with the present study as well as other results in the literature.

Diagnostic tests for Alzheimer's disease: rationale, methodology, and challenges

There has been a large increase in the amount of research seeking to define or diagnose Alzheimer's disease before patients develop dementia. If successful, this would principally have clinical benefits both in terms of treatment as well as risk modification. Moreover, a better method for diagnosing predementia disease would assist research which seeks to develop such treatments and risk modification strategies. The evidence-based definition of a diagnostic test's accuracy is fundamental to achieve the above goals and to address this, the Cochrane Collaboration has established a Diagnostic Test Accuracy group dedicated to examining the utility and accuracy of proposed tests in dementia and cognitive impairment. We present here the assumptions and observations underpinning the chosen methodology as well as the initial methodological approach decided upon.

Sex differences in thrombosis in mice are mediated by sex-specific growth hormone secretion patterns

Sex differences in thrombosis are well described, but their underlying mechanism(s) are not completely understood. Coagulation proteins are synthesized in the liver, and liver gene expression is sex specific and depends on sex differences in growth hormone (GH) secretion--males secrete GH in a pulsatile fashion, while females secrete GH continuously. Accordingly, we tested the hypothesis that sex-specific GH secretion patterns cause sex differences in thrombosis. Male mice were more susceptible to thrombosis than females in the thromboplastin-induced pulmonary embolism model and showed shorter clotting times ex vivo. GH-deficient little (lit) mice were protected from thrombosis, and pulsatile GH given to lit mice restored the male clotting phenotype. Moreover, pulsatile GH administration resulted in a male clotting phenotype in control female mice, while continuous GH caused a female clotting phenotype in control male mice. Expression of the coagulation inhibitors Proc, Serpinc1, Serpind1, and Serpina5 were strongly modulated by sex-specific GH patterns, and GH modulated resistance to activated protein C. These results reveal what we believe to be a novel mechanism whereby sex-specific GH patterns mediate sex differences in thrombosis through coordinated changes in the expression of coagulation inhibitor genes in the liver.

Structure and polarization in the high Tc ferroelectric Bi(Zn,Ti)O3-PbTiO3 solid solutions

Theoretical ab initio and experimental methods are used to investigate the [Bi(Zn1/2Ti1/2)O3]x[PbTiO3]1-x solid solution. We find that hybridization between Zn 4s and 4p and O 2p orbitals allows the formation of short, covalent Zn-O bonds, enabling favorable coupling between A-site and B-site displacements. This leads to unusually large polarization, strong tetragonality, and an elevated ferroelectric to paraelectric phase transition temperature.

Adsorbate−Adsorbate Interactions and Chemisorption at Different Coverages Studied by Accurate ab initio Calculations: CO on Transition Metal Surfaces

We use density functional theory (DFT) with the generalized gradient approximation (GGA) and our first-principles extrapolation method for accurate chemisorption energies (Mason et al. Phys. Rev. B 2004, 69, 161401R) to calculate the chemisorption energy for CO on a variety of transition metal surfaces for various adsorbate densities and patterns. We identify adsorbate through-space repulsion, bonding competition, and substrate-mediated electron delocalization as key factors determining the preferred chemisorption patterns for different metal surfaces and adsorbate coverages. We discuss how the balance of these interactions, along with the inherent adsorption site preference on each metal surface, can explain the observed CO adsorbate patterns at different coverages.

Safe sex and first-episode schizophrenia

The need for educating patients about the dangers of unprotected sexual activity is well documented in the literature. Using clinical examples, the authors describe safe-sex strategies for patients experiencing their first episode of schizophrenia. Interventions are based on a 2-year experience of working in a hospital-based treatment and research project with 68 patients. Strategies that begin in the healing phase of schizophrenia take place in both individual and group sessions. First-episode patients are encouraged to speak explicitly about their sex-related behaviors, and HIV testing is suggested when needed. The goal of this approach is to emphasize safe-sex/HIV prevention strategies within a framework of good clinical practice.

Phase-specific psychosocial interventions for first-episode schizophrenia

Phase-specific psychosocial interventions for first-episode schizophrenia are outlined and described using examples from clinical practice with 68 patients. These interventions are based on the unique aspects of the first episode and patients' clinical states. Although schizophrenia may run an uneven and often unpredictable course, most patients experience three distinct phases: (1) the acute phase, (2) the healing phase, and (3) the maintenance phase. The timeliness of phase-specific interventions is crucial in helping both patients and families understand the illness, evaluate options, accept treatment, and adjust to changes in functioning and expectations.

Use of the ornithine decarboxylase promoter to achieve N-MYC-mediated overexpression of a rabbit carboxylesterase to sensitize neuroblastoma cells to CPT-11

Overexpression of specific transcription factors by tumor cells can be exploited to regulate expression of proteins that induce apoptosis or activate prodrugs, thereby producing tumor-selective toxicity. A majority of advanced-stage neuroblastomas overexpress the transcription factor N-MYC, and this overexpression is associated with poor prognosis. This study describes regulation of expression by N-MYC, via the ornithine decarboxylase (ODC) promoter, of a rabbit liver carboxylesterase (CE) that activates the prodrug CPT-11. Chloramphenicol acetyltransferase reporter assays and CE activity assays in transiently transfected neuroblastoma cell lines (SJNB-1, SJNB-4, NB-1691) and rhabdomyosarcoma cell lines (JR1neo20, JR1Nmyc6, JR1Nmyc9) support this approach as a potential method for sensitizing tumor cells to CPT-11. Clonogenic assays with IMR32 human neuroblastoma cells which express N-MYC and that had been stably transfected with a plasmid containing an ODC promoter/CE cassette corroborated results of enzyme activity assays. Specifically, IMR32.ODC.CE cells expressed approximately eightfold more CE activity than IMR32.CMV.neo cells; and 5 microM CPT-11 reduced the clonogenic potential of IMR32.ODC.CE cells to zero, while 50 microM CPT-11 was required to produce the same effect with IMR32.CMV.neo cells. Current experiments focus on adenoviral delivery of an ODC promoter/CE cDNA cassette for potential virus-directed enzyme prodrug therapy applications.

Clinical trials and tribulations: implementation processes in schizophrenia research outcome

This article focuses on an area in clinical drug trials for new antipsychotic medications for the treatment of schizophrenia which has not received sufficient attention in the literature: the day-to-day implementation tasks performed by research staff which have potential effects on study results. Implementation tasks are viewed as dynamic processes involving interactions among research and nonresearch staff, patients, families, and pharmaceutical company staff. Research-related demands and possible sources of stress for all participants in the process, such as recruiting and maintaining patients in studies, are discussed. Suggestions are offered for increasing the ease of participation. Further investigation is called for in several areas including variability in the effectiveness of research teams and in the rarely discussed interactions between site staff and pharmaceutical company personnel, as they may affect research outcomes. It is posited that increased knowledge about implementation processes in schizophrenia drug development is needed to more fully understand study results and to enhance patients' and their families' willingness to participate.

Instability of individual differences in the association between confidence judgments and memory performance

There are large individual differences in the degree of association between the accuracy of memories and subjective confidence in those memories. Are these differences stable within the same test, and between alternate forms of a test? In Experiment 1, college students were tested on 3 recognition memory tasks, then retested 2 weeks later on alternate forms of the same tasks. The relationship between confidence judgments and recognition performance displayed low split-half stability and low alternate-forms stability. A second experiment with elderly adults replicated these findings. In a third experiment, college students recalled answers to general knowledge questions and rated confidence in the correctness of each answer. Individual differences in the association between confidence and recall performance were not stable across the odd- and even-numbered items on the test. These data indicate the need for the development of procedures that will produce stable estimates of individuals' metacognitive accuracy.

Maintenance imipramine therapy for secondary depression in schizophrenia. A controlled trial

BACKGROUND

Although recent studies have documented the benefit of adjunctive antidepressant medication for the short-term treatment of certain patients with operationally defined syndromes of postpsychotic depression, the value of maintenance adjunctive antidepressant treatment in this circumstance has not been properly established.

METHODS

This study examined 24 schizophrenic or schizoaffective patients with postpsychotic depression or negative symptoms. These patients had all been benefited over the short term by the addition of adjunctive imipramine hydrochloride to their ongoing fluphenazine decanoate/benztropine mesylate regimens, and this adjunctive treatment had been successfully continued for 6 months. In a randomized double-blind protocol, treatment with adjunctive imipramine hydrochloride (mean, 233 +/- 72 mg/d) was then either maintained or tapered to placebo for an ensuing 1-year trial, while treatment with fluphenazine and benztropine continued.

RESULTS

Significantly more patients who received placebo substitution relapsed into depression (P < .001). Patients who received placebo substitution were also more likely to experience relapses into psychosis (P < .02).

CONCLUSIONS

These results support the clinical value of maintenance adjunctive imipramine therapy among initially responsive patients with postpsychotic depressions.