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NiO-based nanomaterials have attracted considerable interest for different applications, which have stimulated the implementation of various synthetic approaches aimed at modulating their chemico-physical properties. In this regard, their bottom-up preparation starting from suitable precursors plays an important role, although a molecular-level insight into their reactivity remains an open issue to be properly tackled. In the present study, we focused on the fragmentation of Ni(II) diketonate-diamine adducts, of interest as vapor-phase precursors for Ni(II) oxide systems, by combining electrospray ionization mass spectrometry (ESI-MS) with multiple collisional experiments (ESI-MSn) and theoretical calculations. The outcomes of this investigation revealed common features in the fragmentation pattern of the target compounds: (i) in the first fragmentation, the three complexes yield analogous base-peak cations by losing a negatively charged diketonate moiety; in these cations, Ni-O and Ni-N interactions are stronger and the Ni positive charge is lower than in the parent neutral complexes; (ii) the tendency of ligand electronic charge to migrate towards Ni further increases in the subsequent fragmentation, leading to the formation of a tetracoordinated Ni environment featuring an interesting cation-π intramolecular interaction. [ABSTRACT FROM AUTHOR]

The relationships between synthetic zeolites and their natural counterparts that have been unveiled by theoretical studies have contributed to improving the properties and applications of zeolite-based materials in strategic areas such as industrial catalysis, environmental protection, and solar energy harvesting. To pinpoint the role of modeling in zeolite science, we discuss an example of computationally driven problem solving: can tetrahedral frameworks sustain straight (i.e., 180°) Si-O-Si bond angles? The true crystal symmetry of zeolite ferrierite (FER), especially in its all-silica form, had been intensely debated for 30 years before being solved in the Pmnn space group. Yet there are indications that an Immm structure with energetically unfavorable linear Si-O-Si linkages could be formed at high temperature. To gather insight, we perform density functional theory (DFT) optimizations and frequency calculations of all-silica ferrierite in both the Pmnn and Immm space groups. Our results indicate that Pmnn is more stable than Immm, in line with experiments. While the Pmnn structure is a true minimum in the energy profile of ferrierite, the Immm structure has four imaginary frequency vibrations, three of which are localized on the 180° Si-O-Si angles. This suggests that ferrierites with Immm symmetry may be classified as metastable phases. Such a designation is also supported by first-principles molecular dynamics on Immm FER, showing that the average value of 180° actually results from Si-O-Si angle inversion. An implication of this study with interesting geological and technological consequences is the association of straight Si-O-Si angles experimentally detected in open-framework or low-density silicates to an angle-inversion process occurring at the femtosecond scale. Such flexibility of the apparently flat Si-O-Si linkages might play an important role in sorption phenomena, which are ubiquitous in geological processes and industrial applications alike. [ABSTRACT FROM AUTHOR]

Carboxylic‐acid adsorption on anatase TiO2 is a relevant process in many technological applications. Yet, despite several decades of investigations, the acid‐proton localization—either on the molecule or on the surface—is still an open issue. By modeling the adsorption of formic acid on top of anatase(101) surfaces, we highlight the formation of a short strong hydrogen bond. In the 0 K limit, the acid‐proton behavior is ruled by quantum delocalization effects in a single potential well, while at ambient conditions, the proton undergoes a rapid classical shuttling in a shallow two‐well free‐energy profile. This picture, supported by agreement with available experiments, shows that the anatase surface acts like a protecting group for the carboxylic acid functionality. Such a new conceptual insight might help rationalize chemical processes involving carboxylic acids on oxide surfaces. [ABSTRACT FROM AUTHOR]

Carboxylic‐acid adsorption on anatase TiO2 is a relevant process in many technological applications. Yet, despite several decades of investigations, the acid‐proton localization—either on the molecule or on the surface—is still an open issue. By modeling the adsorption of formic acid on top of anatase(101) surfaces, we highlight the formation of a short strong hydrogen bond. In the 0 K limit, the acid‐proton behavior is ruled by quantum delocalization effects in a single potential well, while at ambient conditions, the proton undergoes a rapid classical shuttling in a shallow two‐well free‐energy profile. This picture, supported by agreement with available experiments, shows that the anatase surface acts like a protecting group for the carboxylic acid functionality. Such a new conceptual insight might help rationalize chemical processes involving carboxylic acids on oxide surfaces. [ABSTRACT FROM AUTHOR]

A combined linear-response–frozen electron-density model has been implemented in a molecular-dynamics scheme derived from an extended Lagrangian formalism. This approach is based on a partition of the electronic charge distribution into a frozen region described by Kim-Gordon theory [J. Chem. Phys. 56, 3122 (1972); J. Chem. Phys. 60, 1842 (1974)] and a response contribution determined by the instantaneous ionic configuration of the system. The method is free from empirical pair potentials and the parametrization protocol involves only calculations on properly chosen subsystems. We apply this method to a series of alkali halides in different physical phases and are able to reproduce experimental structural and thermodynamic properties with an accuracy comparable to Kohn-Sham density-functional calculations. [ABSTRACT FROM AUTHOR]

A computationally efficient molecular dynamics implementation of a polarizable force field parametrized from ab initio data is presented. Our formulation, based on a second-order expansion of the energy density, models the density response using Gaussian basis functions derived from density functional linear response theory. Polarization effects are described by the time evolution of the basis function coefficients propagated via an extended Lagrangian formalism. We have devised a general protocol for the parametrization of the force field. We will show that a single parametrization of the model can describe the polarization effects of LiI in the condensed phase. [ABSTRACT FROM AUTHOR]

Demonstrates how one-dimensional ice is stabilized by dipolar host/guest interactions in zeolite bikitaite. Demonstration of the stability of the water chain in all simulations; Use of first-principles methods to study different silicon and aluminum ordering in the zeolite framework.

Confinement of molecules in one dimensional arrays of channel-shaped cavities has led to technologically interesting materials. However, the interactions governing the supramolecular aggregates still remain obscure, even for the most common guest molecule: water. Herein, we use computational chemistry methods (#compchem) to study the water organization inside two different channel-type environments: zeolite L – a widely used matrix for inclusion of dye molecules, and ZLMOF – the closest metal-organic-framework mimic of zeolite L. In ZLMOF, the methyl groups of the ligands protrude inside the channels, creating nearly isolated nanocavities. These cavities host well-separated ring-shaped clusters of water molecules, dominated mainly by water-water hydrogen bonds. ZLMOF provides arrays of "isolated supramolecule" environments, which might be exploited for the individual confinement of small species with interesting optical or catalytic properties. In contrast, the one dimensional channels of zeolite L contain a continuous supramolecular structure, governed by the water interactions with potassium cations and by water-water hydrogen bonds. Water imparts a significant energetic stabilization to both materials, which increases with the water content in ZLMOF and follows the opposite trend in zeolite L. The water network in zeolite L contains an intriguing hypercoordinated structure, where a water molecule is surrounded by five strong hydrogen bonds. Such a structure, here described for the first time in zeolites, can be considered as a water pre-dissociation complex and might explain the experimentally detected high proton activity in zeolite L nanochannels. [ABSTRACT FROM AUTHOR]

Confined supramolecular architectures of chromophores are key components in artificial antenna composites for solar energy harvesting and storage. A typical fabrication process, based on the insertion of dye molecules into zeolite channels, is still unknown at the molecular level. We show that slipping of perylene diimide dyes into the one-dimensional channels of zeolite L and travelling inside is only possible because of steric-interaction-induced cooperative vibrational modes of the host and the guest. The funnel-like structure of the channel opening, larger at the entrance, along with a directionally asymmetric entrance–exit probability, ensures a favorable self-assembly process of the perylene units. [ABSTRACT FROM AUTHOR]

Octyl methoxycinnamate (2-ethylhexyl 4-methoxycinnamate, OMC) is a commercial sunscreen known as octinoxate with excellent UVB filter properties. However, it is known to undergo a series of photodegradation processes that decrease its effectiveness as a UVB filter. In particular, the trans (E) form—which is considered so far as the most stable isomer—converts to the cis (Z) form under the effect of light. In this work, by using post-Hartree–Fock approaches [CCSD, CCSD(t), and CCSD + T(CCSD)] on ground state OMC geometries optimized at the MP2 level, we show that the cis and trans forms of the gas-phase OMC molecule have comparable stability. Test calculations on the same structures with a series of dispersion-corrected density functional theory-based approaches including the B2PLYP double hybrid predict the trans structures to be energetically favored, missing the subtle stabilization of cis-OMC. Our results suggest that the cis form is stabilized by intra-molecular dispersion interactions, leading to a folded more compact structure than the trans isomer. [ABSTRACT FROM AUTHOR]

Multifunctional hybrid materials are obtained by modifying zeolite L (ZL) with stopcock molecules, consisting of a tail group that can enter the ZL nanochannels and a head group too large to pass the channel opening. However, to date no microscopic-level structural information on modified ZL materials has been reported. Herein we draw atomistic pictures of channel openings and stopcock-functionalized ZL based on first-principles calculations. We elucidate the interactions of the tail group with the inner surface of ZL channels and the space-filling properties of the stopcocks, revealing cork- or lid-sealing modes. Water is essential to obtain stable modifications. AlOH groups are the preferred modification sites, bipodal modifications suffer from strain, and tripod binding is ruled out. Our results suggest the viability of recursive functionalization by cross-linking. [ABSTRACT FROM AUTHOR]

Multifunctional hybrid materials are obtained by modifying zeolite L (ZL) with stopcock molecules, consisting of a tail group that can enter the ZL nanochannels and a head group too large to pass the channel opening. However, to date no microscopic-level structural information on modified ZL materials has been reported. Herein we draw atomistic pictures of channel openings and stopcock-functionalized ZL based on first-principles calculations. We elucidate the interactions of the tail group with the inner surface of ZL channels and the space-filling properties of the stopcocks, revealing cork- or lid-sealing modes. Water is essential to obtain stable modifications. AlOH groups are the preferred modification sites, bipodal modifications suffer from strain, and tripod binding is ruled out. Our results suggest the viability of recursive functionalization by cross-linking. [ABSTRACT FROM AUTHOR]

Integrated analyses on a series of β-diketonate-diamine transition metal complexes (M = Fe, Co, Cu, Zn) highlight the metal center influence on molecular physico-chemical properties and provide understanding of the favorable behavior of these compounds as precursors in the chemical vapor deposition (CVD) growth of metal/metal oxide nanomaterials. The Zn complex, which shows the most symmetric coordination environment in the gas phase, is activated in contact with the heated CVD growth surface model. First-principles simulations evidenced surface-induced rolling motion of the Zn precursor in the 363-750 K range, suggesting the relevance of vibrationally excited molecular rolling as activation pathway in high temperature surface chemistry. Molecular properties (left) and hot-surface behavior (right) of the Zn(hfa)2TMEDA CVD precursor. [ABSTRACT FROM AUTHOR]

First-principles modeling can be a powerful tool for the understanding and optimization of bottom-up processes for nanomaterials fabrication, such as chemical vapor deposition (CVD), a key technology for the development of advanced systems and devices. Molecule-to-material conversion by CVD involves complex chemical phenomena, which are often obscure and still largely unexplored. A proper modeling would require high level of accuracy, large sized models and should include both temperature effects and statistical sampling of reactive events. By presenting a few selected examples, this perspective surveys such problems and discusses currently available approaches for their solution. Possible strategies for future advances in the field are also highlighted. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A combined experimental and modelingstudy of methylacridine (MeAcr+) dye-zeolite L compositesunravels the microscopic originof their functional properties. The anisotropic orientation of thecationic dye inside the ZL channel is unambiguously determined andunderstood. The most stable orientation of MeAcr+, whichfeatures both its long and short molecular axes nearly perpendicularto the channel axis, is mainly determined by dye-ZL electrostaticinteractions but also depends on the cosolvent water. In ZL, MeAcr+is not hydrogen bonded to water or ZL framework oxygens andis hydrophobically solvated by water molecules. These findings furthersupport the hypothesis that the cosolvent can importantly influenceproperties of dye–zeolite composites. Of relevance for a deepercomprehension of the physical chemistry of these hybrids is the observationthat trivial energy transfer processes (self-absorption) are oftenplaying a significant role in the optical properties of the composites. [ABSTRACT FROM AUTHOR]

First principles studies on periodic TS-1 models at Ti content corresponding to 1.35% and 2.7% in weight of TiO2are presented. The problem of Ti preferential siting is addressed by using realistic models corresponding to the TS-1 unit cell [TiSi95O192] and adopting for the first time a periodic DFT approach, thus providing an energy scale for Ti in the different crystallographic sites in nondefective TS-1. The structure with Ti in site T3 is the most stable, followed by T4 (+0.3 kcal/mol); the less stable structure, corresponding to Ti in T1, is 5.6 kcal/mol higher in energy. The work has been extended to investigate models with two Ti’s per unit cell [Ti2Si94O192] (2.7%). The possible existence of Ti−O−Ti bridges, formed by two corner-sharing TiO4tetrahedra, is discussed. By using cluster models cut from the optimized periodic DFT structures, both vibrational (DFT) and electronic excitation spectra (TDDFT) have been calculated and favorably compared with the experimental data available on TS-1. Interesting features emerged from excitation spectra: (i) Isolated tetrahedral Ti sites show a Beer−Lambert behavior, with absorption intensity proportional to concentration. Such a behavior is gradually lost when two Ti’s occupy sites close to each other. (ii) The UV−vis absorption in the 200−250 nm region can be associated with transitions from occupied states delocalized on the framework oxygens to empty d states localized on Ti. Such extended-states-to-local-states transitions may help the interpretation of the photovoltaic activity recently detected in Ti zeolites. [ABSTRACT FROM AUTHOR]

First principles molecular dynamics studies on active-site models of flavocytochrome b2 (l-lactate : cytochrome c oxidoreductase, Fcb2), in complex with the substrate, were carried out for the first time to contribute towards establishing the mechanism of the enzyme-catalyzedl-lactate oxidation reaction, a still-debated issue. In the calculated enzyme–substrate model complex, thel-lactate α-OH hydrogen is hydrogen bonded to the active-site base H373 Nε, whereas the Hα is directed towards flavin N5, suggesting that the reaction is initiated by α-OH proton abstraction. Starting from this structure, simulation ofl-lactate oxidation led to formation of the reduced enzyme–pyruvate complex by transfer of a hydride from lactate to flavin mononucleotide, without intermediates, but with α-OH proton abstraction preceding Hα transfer and a calculated free energy barrier (12.1 kcal·mol−1) consistent with that determined experimentally (13.5 kcal·mol−1). Simulation results also revealed features that are of relevance to the understanding of catalysis in Fcb2 homologs and in a number of flavoenzymes. Namely, they highlighted the role of: (a) the flavin mononucleotide–ribityl chain 2′OH group in maintaining the conserved K349 in a geometry favoring flavin reduction; (b) an active site water molecule belonging to a S371–Wat–D282–H373 hydrogen-bonded chain, conserved in the structures of Fcb2 family members, which modulates the reactivity of the key catalytic histidine; and (c) the flavin C4a–C10a locus in facilitating proton transfer from the substrate to the active-site base, favoring the initial step of the lactate dehydrogenation reaction. [ABSTRACT FROM AUTHOR]

Highlights from the article: Titelbild: The Case of Formic Acid on Anatase TiO2(101): Where is the Acid Proton? Die Minderung von NO SB I x i sb -Emissionen durch Vanadiumoxid-basierte Katalysatoren wird durch Zusatz von Wolframoxid verstärkt, wie J. Z. Hu, Y. Wang, I. E. Wachs et al. in ihrem Forschungsartikel auf S. 12739 zeigen. In ihrer Zuschrift auf S. 12528 beschreiben M. Chiesa und Mitarbeiter die aktiven Zentren in einem MFI-Zeolith mittels selektiver SP 17 sp O-Isotopenanreicherung und der einzigartigen Eigenschaften offenschaliger monovalenter Gruppe-12-Kationen.

Incorporation of biological systems in water nanodroplets has recently emerged as a new frontier to investigate structural changes of biomolecules, with perspective applications in ultra-fast drug delivery. We report on the molecular dynamics of the digestive protein Pepsin subjected to a double confinement. The double confinement stemmed from embedding the protein inside a water nanodroplet, which in turn was caged in a nanochannel mimicking the mesoporous silica SBA-15. The nano-bio-droplet, whose size fits with the pore diameter, behaved differently depending on the protonation state of the pore surface silanols. Neutral channel sections allowed for the droplet to flow, while deprotonated sections acted as anchoring piers for the droplet. Inside the droplet, the protein, not directly bonded to the surface, showed a behavior similar to that reported for bulk water solutions, indicating that double confinement should not alter its catalytic activity. Our results suggest that nanobiodroplets, recently fabricated in volatile environments, can be encapsulated and stored in mesoporous silicas. [ABSTRACT FROM AUTHOR]

NiO-based films and nanostructured materials have received increasing attention for a variety of technological applications. Among the possible strategies for their fabrication, atomic layer deposition (ALD) and chemical vapor deposition (CVD), featuring manifold advantages of technological interest, represent appealing molecule-to-material routes for which a rational precursor design is a critical step. In this context, the present study is focused on the coordination sphere engineering of three heteroleptic Ni(II) β-diketonate–diamine adducts of general formula [NiL2TMEDA] [L = 1,1,1-trifluoro-2,4-pentanedionate (tfa), 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedionate (fod) or 2,2,6,6-tetramethyl-3,5-heptanedionate (thd), and TMEDA = N,N,N′,N′-tetramethylethylenediamine]. Controlled variations in the diketonate structure are pursued to investigate the influence of steric hindrance and fluorination degree on the chemico-physical characteristics of the compounds. A multi-technique investigation supported by density functional calculations highlights that all complexes are air-insensitive and monomeric and that their thermal properties and fragmentation patterns are directly dependent on functional groups in the diketonate ligands. Preliminary thermal CVD experiments demonstrate the precursors' suitability for the obtainment of NiO films endowed with flat and homogeneous surfaces, paving the way to future implementation for CVD end-uses. [ABSTRACT FROM AUTHOR]

The molecular origin of the behavior of a class of transition metal complexes, attractive as sources for the chemical vapor deposition (CVD) growth of metal/metal oxide nanomaterials, is unraveled by integrated modeling studies. In the paper on pp. 251–259, Tabacchi et al. show how the metal center affects the properties of a series of β‐diketonate‐diamine metal complexes (M = Fe, Co, Cu, Zn), by focusing on the growth‐temperature influence on the first molecular activation stages. A key milestone of the present work is the observation of hot‐surface induced molecular rolling for Zn(hfa)2TMEDA, the complex with the most symmetric coordination polyhedron in the gas phase. Such a rolling motion occurs at temperatures even lower than those normally adopted in CVD processes and causes rearrangement of the ligands around the metal center. Variations in the behavior of different metal complexes might be at the origin of different decomposition pathways at the growth surface, enabling thus to shed light on the molecule‐to‐material conversion processes and to tailor the initial nucleation stages of the target nanomaterials by design. [ABSTRACT FROM AUTHOR]

Abstract: The dehydration of model mesoporous silicas has been studied via molecular dynamics simulations. By progressively dehydrating the system, initially characterized by an even distribution of surface silanols, patches with hydrophobic or hydrophilic character are formed on the pores surface. It is found that the local concentration of silanols is strictly correlated to the local structure of pores surface, namely hydrophobic and hydrophilic patches are located in high- and low-curvature surface regions, respectively, in line with experimental evidences. Simulations suggest that the microscopic origin of both the uneven Si–OH distribution and the pores surface deformation should be related to the dehydroxylation process, which is governed by interactions among the silica matrix. [Copyright &y& Elsevier]

The microscopic behavior of the Ca-zeolite yugawaralite has been studied by ab initio molecular dynamics simulations adopting experimental cell parameters obtained at pressures up to ∼9 GPa. Pressure-induced volume contraction occurs via rotations of quasi-rigid TO4 tetrahedra that reduce the size of the channels in which the extra-framework species are located. Such rotations are governed by deformation of the coordination polyhedron of Ca, which is made up of water and framework O atoms. Contraction of the Ca-H2O distances is favored at moderate pressure; at higher pressure the shortening of Ca-framework O atom distances becomes prevalent. The hydrogen bond network plays a fundamental role in the overall response to pressure. Our results indicate that the high-P-induced deformation of the framework structure is strictly correlated to the extra-framework species that act as "templates" in the compression process. [ABSTRACT FROM AUTHOR]

Co3O4 thin films and nanosystems are implemented in a broad range of functional systems, including gas sensors, (photo)catalysts, and electrochemical devices for energy applications. In this regard, chemical vapor deposition (CVD) is a promising route for the fabrication of high-quality films in which the precursor choice plays a key role in the process development. In this work, a heteroleptic cobalt complex bearing fluorinated diketonate ligands along with a diamine moiety [Co(tfa)2·TMEDA; tfa = 1,1,1-trifluoro-2,4-pentanedionate and TMEDA = N,N,N′,N′-tetramethylethylenediamine] is investigated as a potential Co molecular precursor for the CVD of Co3O4 systems. For the first time, the compound is characterized by crystal structure determination and comprehensive analytical studies, focusing also on its thermal properties and fragmentation patterns, important figures of merit for a CVD precursor. The outcomes of this investigation, accompanied by detailed theoretical studies, highlight its very favorable properties for CVD applications. In fact, growth experiments under oxygen atmospheres containing water vapor revealed the suitability of Co(tfa)2·TMEDA for the fabrication of high-quality, phase-pure Co3O4 thin films. The versatility of the proposed strategy in tailoring Co3O4 structural/morphological features highlights its potential to obtain multi-functional films with controllable properties for a variety of eventual technological end-uses. [ABSTRACT FROM AUTHOR]

The general principles guiding the design of molecular machines based on interlocked structures are well known. Nonetheless, the identification of suitable molecular components for a precise tuning of the energetic parameters that determine the mechanical link is still challenging. Indeed, what are the reasons of the "all‐or‐nothing" effect, which turns a molecular "speed‐bump" into a stopper in pseudorotaxane‐based architectures? Here we investigate the threading and dethreading processes for a representative class of molecular components, based on symmetric dibenzylammonium axles and dibenzo[24]crown‐8 ether, with a joint experimental–computational strategy. From the analysis of quantitative data and an atomistic insight, we derive simple rules correlating the kinetic behaviour with the substitution pattern, and provide rational guidelines for the design of modules to be integrated in molecular switches and motors with sophisticated dynamic features. [ABSTRACT FROM AUTHOR]

The general principles guiding the design of molecular machines based on interlocked structures are well known. Nonetheless, the identification of suitable molecular components for a precise tuning of the energetic parameters that determine the mechanical link is still challenging. Indeed, what are the reasons of the "all‐or‐nothing" effect, which turns a molecular "speed‐bump" into a stopper in pseudorotaxane‐based architectures? Here we investigate the threading and dethreading processes for a representative class of molecular components, based on symmetric dibenzylammonium axles and dibenzo[24]crown‐8 ether, with a joint experimental–computational strategy. From the analysis of quantitative data and an atomistic insight, we derive simple rules correlating the kinetic behaviour with the substitution pattern, and provide rational guidelines for the design of modules to be integrated in molecular switches and motors with sophisticated dynamic features. [ABSTRACT FROM AUTHOR]

This study is aimed to shed light on the mechanisms at the basis of the differential penetration of alcohol and water in hydrophobic zeolites at ambient (P amb) and non-ambient pressure. Here we report the effects of the penetration of water and alcohol in an all-silica chabazite (Si-CHA) compressed with an ethanol/water azeotrope solution (ethanol: water = 95.63 : 4.37 by mass %). We collected in situ synchrotron X-ray Powder Diffraction (XRPD) data in order to monitor the structural modifications induced by the fluid penetration and to investigate the guest-guest and host-guest interactions. First principles molecular dynamics simulations allowed to complete the structural description at high pressure, providing an atomistic level description of the guest-guest hydrogen bond network. For a comprehensive understanding of the processes involving the Si-CHA + azeotrope interactions, both the zeolite and the alcohol/water solution were firstly investigated separately under pressure. The results obtained prove that both H 2 O and ethanol penetrate Si-CHA porosities even at P amb. However, while in these conditions the H 2 O/ethanol ratio adsorbed inside Si-CHA is similar to that of the external azeotrope solution, under pressure the zeolite extra-framework content corresponds to a composition much richer in H 2 O than the azeotrope one. Hence, our results suggest that a dehydration effect occurred on the azeotrope solution, promoted by pressure. In addition, the experiment performed to test the elastic behavior of Si-CHA with a non-penetrating pressure transmitting medium interestingly indicates that Si-pure chabazite is the most compressible zeolite among those up to now studied in silicone oil. Image 1 • Both H 2 O and ethanol molecules penetrate Si chabazite under pressure. • Pressure promotes the dehydration of ethanol/water azeotrope solutions through adsorption in Si chabazite. • Si chabazite compressed in silicone oil displays a phase transition rhombohedral/triclinic at about 1.42 GPa. • Si chabazite is one of the most compressible zeolites. [ABSTRACT FROM AUTHOR]

Molecular engineering of manganese(II) diamine diketonate precursors is a key issue for their use in the vapor deposition of manganese oxide materials. Herein, two closely related β-diketonate diamine MnII adducts with different fluorine contents in the diketonate ligands are examined. The target compounds were synthesized by a simple procedure and, for the first time, thoroughly characterized by a joint experimental-theoretical approach, to understand the influence of the ligand on their structures, electronic properties, thermal behavior, and reactivity. The target compounds are monomeric and exhibit a pseudo-octahedral coordination of the MnII centers, with differences in their structure and fragmentation processes related to the ligand nature. Both complexes can be readily vaporized without premature side decompositions, a favorable feature for their use as precursors for chemical vapor deposition (CVD) or atomic layer deposition applications. Preliminary CVD experiments at moderate growth temperatures enabled the fabrication of high-purity, single-phase Mn3O4 nanosystems with tailored morphology, which hold great promise for various technological applications. [ABSTRACT FROM AUTHOR]

Turning disorder into organization is a key issue in science. By making use of X-ray powder diffraction and modeling studies, we show herein that high pressures in combination with the shape and space constraints of the hydrophobic all-silica zeolite ferrierite separate an ethanol-water liquid mixture into ethanol dimer wires and water tetramer squares. The confined supramolecular blocks alternate in a binary two-dimensional (2D) architecture that remains stable upon complete pressure release. These results support the combined use of high pressures and porous networks as a viable strategy for driving the organization of molecules or nano-objects towards complex, pre-defined patterns relevant for the realization of novel functional nanocomposites. [ABSTRACT FROM AUTHOR]

Turning disorder into organization is a key issue in science. By making use of X-ray powder diffraction and modeling studies, we show herein that high pressures in combination with the shape and space constraints of the hydrophobic all-silica zeolite ferrierite separate an ethanol-water liquid mixture into ethanol dimer wires and water tetramer squares. The confined supramolecular blocks alternate in a binary two-dimensional (2D) architecture that remains stable upon complete pressure release. These results support the combined use of high pressures and porous networks as a viable strategy for driving the organization of molecules or nano-objects towards complex, pre-defined patterns relevant for the realization of novel functional nanocomposites. [ABSTRACT FROM AUTHOR]

[Display omitted] • Benzofulvene derivatives 6-Pyr- BF3k and 6-PTPC- BF3k bearing uncomplexed and complexed pyridine rings are synthesized. • The solvent removal from a 6-Pyr- BF3k solution leads to the spontaneous formation of the homopolymer poly-6-Pyr- BF3k. • The same procedure applied to the 6-PTPC- BF3k monomer highlights the competition between polymerization and crystallization. • Uncomplexd poly-6-Pyr- BF3k show interesting emission properties, while poly-6-PTPC- BF3k shows low emission quantum yield. Benzofulvene derivatives bearing complexed and un-complexed pyridine rings are designed and synthesized to assess the effects on the spontaneous solid-state polymerization of the presence in position 6 of the 3-phenylbenzofulvene moiety of bulky substituents capable of establishing metallophilic interactions. Both the benzofulvene monomers are found to polymerize spontaneously upon solvent removal under reduced pressure in the apparent absence of catalysts or initiators. The resulting polybenzofulvene derivatives are characterized by NMR spectroscopy, MALDI-TOF mass spectrometry, and in photophysical studies. [ABSTRACT FROM AUTHOR]

Iron(III) oxide nanomaterials are extremely promising for the development of magnetic devices, gas sensors, photocatalysts, and photoelectrodes for solar water splitting. The fabrication of such systems by chemical vapor deposition (CVD) relies on the use of molecular sources joining shelf-stability, high volatility, and clean decomposition. Herein, we report for the first time on a versatile iron(II) precursor, namely Fe(tfa) 2 TMEDA (tfa = 1,1,1-trifluoro-2,4-pentanedionate; TMEDA = N , N , N′ , N′ -tetramethylethylenediamine), combining the above features with a simple molecular concept. A theoretical-experimental characterization confirmed the compound spectroscopic purity and monomeric nature, and enabled to elucidate its structural, vibrational and electronic properties, along with its fragmentation pathway and thermal behavior. The ideal Fe(tfa) 2 TMEDA characteristics for CVD applications were finally validated through the fabrication of high purity iron oxide nanomaterials. The latter, comprising the sole metastable β-Fe 2 O 3 polymorph rather than the most stable rust (α-Fe 2 O 3), were characterized by the occurrence of oxygen defects and a nano-organization tunable as a function of growth temperature and reaction atmosphere. [Display omitted] • An iron(II) diketonate-diamine precursor is proposed for CVD of Fe 2 O 3 nanomaterials. • A theoretical/experimental approach is adopted for Fe(tfa) 2 TMEDA characterization. • A pure adduct with a fully saturated Fe(II) coordination sphere is obtained. • The complex has a high shelf stability, a good volatility and a clean fragmentation. • The compound validation in CVD afforded the scarcely investigated β-Fe 2 O 3 polymorph. [ABSTRACT FROM AUTHOR]

Abstract: The preparation of the second generation iron(II) complex Fe(hfa)2·TMEDA (hfa=1,1,1,5,5,5-hexafluoro-2,4-pentanedionate, TMEDA= N,N,N′,N′-tetramethylethylenediamine) is performed by reacting iron(II) chloride with Hhfa and TMEDA in two subsequent steps. Density functional theory data show that the compound possesses a distorted octahedral geometry, with the two β-diketonate ligands in a cis configuration. The complex mass transport properties and fragmentation pattern are investigated by thermal analyses and electron impact mass spectrometry, respectively. In addition, its experimental and simulated IR spectra are presented. For the first time, Fe(hfa)2·TMEDA was successfully applied in the chemical vapor deposition (CVD) of iron oxide on Si(100). Structural, compositional and morphological analyses evidence the possibility of obtaining pure, single-phase and homogeneous β-Fe2O3 films. [Copyright &y& Elsevier]

Abstract: Gibbs ensemble Monte Carlo simulations were carried out to investigate the properties of a frozen-electron-density (or Kim–Gordon, KG) model of water along the vapor–liquid coexistence curve. Because of its theoretical basis, such a KG model provides for seamless coupling to Kohn–Sham density functional theory in mixed quantum mechanics/molecular mechanics implementations. The Gibbs ensemble simulations indicate limited transferability of a KG model to other state points. Specifically, a KG model that was parameterized by Barker and Sprik to the properties of liquid water at 300K, yields saturated vapor pressures and a critical temperature that are significantly under- and overestimated, respectively. [Copyright &y& Elsevier]

High-temperature behavior and the process of thermal dehydration in the natural zeolite bikitaite have been studied by ab initio molecular dynamics simulations, and favorably compared with the X-ray powder diffraction data presented in Part I of this work (Ferro et al. 2003). The microscopic dynamical behavior of the extraframework species (water molecules and Li cations) has been characterized as a function of temperature. Two regimes have been detected, and the transition is characterized by the breaking of the one-dimensional water chain typical of bikitaite at room temperature. The elementary steps for the diffusion of water inside the bikitaite channels have been studied by means of a rare-events-sampling technique (Bluemoon Ensemble). The activation free-energy for a site-to-site water jump has been calculated and a mechanism for the dehydration process is proposed. [ABSTRACT FROM AUTHOR]

The HP behavior of the natural zeolite yugawaralite and of the synthetic zeolite Na-A was studied by in situ synchrotron X-ray powder diffraction, using a non-penetrating P-transmitting medium. The unit-cell parameters of yugawaralite were refined up to the pressure of 10 GPa, at which reductions were found of about 7, 2.4, 7, 1.3, and 15% for a, b, c, β, and V, respectively. Contractions of 6.5 and 18.4% were found for a and V, respectively, for zeolite Na-A in the range 10[sup-4] to 6.8 GPa. Diffraction patterns collected during decompression show that the effects induced by high pressure on both samples are almost completely reversible. These results are compared with those obtained under similar experimental conditions for other natural zeolites, with the aim of rationalizing the deformation mechanisms of these porous materials and comparing their flexibility under high-pressure and high-temperature conditions. [ABSTRACT FROM AUTHOR]

A simulation study on the rotational behavior of neutral and charged molecular systems hosted in zeolitic cages is presented here. Synthetic sodalites containing both molecular (O2) and anionic (NO2−, NO3−) species and an hydrated Ti-offretite have been simulated by first-principles molecular dynamics. Our results show that both host–guest and guest–guest interactions directly influence the rotational motion of the caged species. [Copyright &y& Elsevier]

Presents a study that examined pressure-induced structural modifications in the zeolite bikitaite by means of in situ synchrotron X-ray powder diffraction and ab initio molecular dynamics. Methodology; Results; Discussion.

Transition metal complexes with β-diketonate and diamine ligands are valuable precursors for chemical vapor deposition (CVD) of metal oxide nanomaterials, but the metal-ligand bond dissociation mechanism on the growth surface is not yet clarified in detail. We address this question by density functional theory (DFT) and ab initio molecular dynamics (AIMD) in combination with the Blue Moon (BM) statistical sampling approach. AIMD simulations of the Zn β-diketonate-diamine complex Zn(hfa)2TMEDA (hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedionate; TMEDA = N,N,N′,N′-tetramethylethylenediamine), an amenable precursor for the CVD of ZnO nanosystems, show that rolling diffusion of this precursor at 500 K on a hydroxylated silica slab leads to an octahedral-to-square pyramidal rearrangement of its molecular geometry. The free energy profile of the octahedral-to-square pyramidal conversion indicates that the process barrier (5.8 kcal/mol) is of the order of magnitude of the thermal energy at the operating temperature. The formation of hydrogen bonds with surface hydroxyl groups plays a key role in aiding the dissociation of a Zn-O bond. In the square-pyramidal complex, the Zn center has a free coordination position, which might promote the interaction with incoming reagents on the deposition surface. These results provide a valuable atomistic insight on the molecule-to-material conversion process which, in perspective, might help to tailor by design the first nucleation stages of the target ZnO-based nanostructures. [ABSTRACT FROM AUTHOR]

Zeolites are known as scaffolds for the assembly of molecules via non-covalent interactions yielding organized supramolecular materials. Yet their potential in driving the growth of low-dimensional systems requiring covalent bond formation is still unexplored. We incorporated 1,5-hexadiene in the channels of a high-silica mordenite and analyzed the material by infrared spectroscopy, X-ray powder diffraction, thermogravimetry and modeling techniques. Due to the few zeolite acid sites, 1,5-hexadiene experiences a slow conversion to a polymer mainly formed by cyclopentane units and featuring short side chains that are able to fit the channels. The shape-directing abilities of zeolite frameworks play a two-fold role, involving first the organization of the monomers inside the void-space and then the linear growth of the chain dictated by the channel geometry. These findings highlight the molding action of zeolites in directing transformations of covalent bonds under ambient conditions and may provide insights for obtaining confined polymers with intriguing prospective applications. Incorporation of 1,5-hexadiene molecules in high-silica mordenite at room temperature produces quasi one-dimensional polymers tailored by the molding action of the zeolite framework. The size/shape constraints of the zeolite channels play a key role in directing molecular organization and bond transformation processes towards polymers that fit like a hand in the glove to the host inner spaces. Image 1 • Intruded hexadiene molecules in pure silica mordenite polymerize into a continuous 1D chain. • Zeolite channels act as a mold shaping the polymer structure among many otherwise possible. • The polymer consists of cyclic units intercalated by short linear side chains. • The polymerization reaction involves all zeolite channels although initiated by a few acid sites. [ABSTRACT FROM AUTHOR]

The joint use of high pressure and regular void-space architectures is a promising route to obtain new nanomaterials with unique properties. We explore herein the pressure-driven injection of aromatic guest species inside zeolite mordenite. Monomeric phenylacetylene (PhA), used as pressure transmitting medium, was inserted in high-silica mordenite at high pressure conditions. In-situ X-ray powder diffraction and IR spectroscopy analyses show that the combined action of high pressure, temperature and zeolite pores accomplish the intrusion of phenylacetylene and its conversion to oligomeric species exhibiting a greater degree of conjugation with respect to the starting monomer. This study may open a new path for the realization of composite materials with interesting optoelectronic properties via pressure-driven intrusion and polymerization of aromatic molecules inside zeolite frameworks. Image 1 • Penetration of phenylacetylene molecule into HS mordenite occurs at very low pressure. • At 0.40 GPa two PhA molecules per unit cell are hosted in HS mordenite. • HT and HP induce a polymerization reaction of the hosted phenylacetylene. [ABSTRACT FROM AUTHOR]

“Wir verehren das Chaos , weil wir es lieben, Ordnung zu schaffen”: Inspiriert von den Arbeiten M. C. Eschers veranschaulicht das Titelbild die Metamorphose einer Ethanol/Wasser ‐ Lösung. Wie G. Tabacchi et al. in der Zuschrift auf S. 2137 ff. beschreiben, ergeben chaotisch verteilte Moleküle ein wunderbar geordnetes zweidimensionales Muster aus Dimeren und Tetrameren. Diese Ordnung entsteht bei hohem Druck und durch Einschluss in nanometergroße Hohlräume (Illustration: Andrea Stangoni). [ABSTRACT FROM AUTHOR]

Discusses the structural and dynamical information on aqueous hydroxides obtained from Car-Parrinello molecular dynamics (CPMD) simulations on five sodium hydroxide/water systems. Calculated oxygen-oxygen radical distribution functions from sodium hydroxide; Expansion of valence electronic wave functions in a plane wave basis; Norm-conserving Troullier-Martins pseudopotentials.