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We present a new general-purpose machine learning model that is able to predict a variety of crystal properties, including Fermi level energy and band gap, as well as spectral ones such as electronic densities of states. The model is based on atomic representations that enable it to effectively capture complex information about each atom and its surrounding environment in a crystal. The accuracy achieved for band gaps exceeds results previously published. By design, our model is not restricted to the electronic properties discussed here but can be extended to fit diverse chemical descriptors. Its advantages are (a) its low computational requirements, making it an efficient tool for high-throughput screening of materials; and (b) the simplicity and flexibility of its architecture, facilitating implementation and interpretation, especially for researchers in the field of computational chemistry.

In high-energy molecular dynamics or Monte Carlo simulations, standard force fields optimized for simulations at ambient temperatures are inadequate. This is largely because their repulsive parts have been regarded as not very significant, even well below zero interaction energies. It is, therefore, not obvious which force fields to resort to for simulating hot gases or plasmas. A force field model that uses the electronic densities of noninteracting atoms or molecules within the pair approximation is introduced. We start by deriving a naïve model that neglects any exchange and correlation effects between the electronic clouds and then correct this model by adding a term calibrated from ab initiocalculations using the CCSD(T)/cc-pVTZ level of theory. The resulting expression for this term can be regarded as a simple exchange–correlation function. We compare the results for the repulsive part of the potential energy hypersurfaces with the force fields commonly used on some dimers of small molecules.

We present a viable mechanism for the conversion of ethanol to acetaldehyde by sustainable heterogeneous catalysis using modified zeolites. The catalytic conversion of ethanol into valuable hydrocarbon compounds is an alternative method for the production of petrochemical feedstock. Here, we calculate the reaction mechanism of the dehydrogenation of ethanol to acetaldehyde over Zn-DeAlBEA by means of density functional theory and coupled cluster calculations. In the reaction mechanisms investigated, high selectivity toward acetaldehyde instead of ethylene is observed, judged by their activation free energies. The zeolite frameworks have a stabilizing effect on all species along the reaction coordinates including intermediates and transition states. The ZnO-DeAlBEA zeolite is compared to Zn-DeAlBEA. With an additional oxygen atom at the Zn surface site, reaction barriers for the ethanol O–H bond dissociation and the acetaldehyde formation become much smaller, while the selectivity toward aldehyde is maintained.

Data-driven science and technology offer transformative tools and methods to science. This review article highlights the latest development and progress in the interdisciplinary field of data-driven plasma science (DDPS), i.e., plasma science whose progress is driven strongly by data and data analyses. Plasma is considered to be the most ubiquitous form of observable matter in the universe. Data associated with plasmas can, therefore, cover extremely large spatial and temporal scales, and often provide essential information for other scientific disciplines. Thanks to the latest technological developments, plasma experiments, observations, and computation now produce a large amount of data that can no longer be analyzed or interpreted manually. This trend now necessitates a highly sophisticated use of high-performance computers for data analyses, making artificial intelligence and machine learning vital components of DDPS. This article contains seven primary sections, in addition to the introduction and summary. Following an overview of fundamental data-driven science, five other sections cover widely studied topics of plasma science and technologies, i.e., basic plasma physics and laboratory experiments, magnetic confinement fusion, inertial confinement fusion and high-energy-density physics, space and astronomical plasmas, and plasma technologies for industrial and other applications. The final Section before the summary discusses plasma-related databases that could significantly contribute to DDPS. Each primary Section starts with a brief introduction to the topic, discusses the state-of-the-art developments in the use of data and/or data-scientific approaches, and presents the summary and outlook. Despite the recent impressive signs of progress, the DDPS is still in its infancy. This article attempts to offer a broad perspective on the development of this field and identify where further innovations are required.

Background: The most widely accepted criteria for the evaluation of prognosis of malignant melanoma are histopathologic and clinical presentation. No currently available laboratory tests provide additional prognostic information. It has recently been suggested that reverse transcription and polymerase chain reaction (RT-PCR)-based detection of tyrosinase messenger RNA (mRNA) in peripheral blood might be useful in the early detection of circulating tumor cells, since tyrosinase is thought to be a melanocyte-specific marker. Purpose: To further evaluate the clinical relevance of this potential marker, we examined peripheral blood samples from patients with malignant melanoma in different stages of disease for the presence of tyrosinase mRNA. Methods: Total cellular RNA was extracted from heparinized peripheral blood cells from 64 patients with malignant melanoma, from rive healthy control subjects, and from four patients with other cancers using the RANzol A method. For analysis of tyrosinase mRNA, RT-PCR was performed as previously described by Smith et al.; the sensitivity of this assay was tested using RNA extracted from human melanoma cells (SK-mel 1 and Sk-mel 3 cell lines) serially diluted with peripheral blood obtained from healthy control subjects. Two additional human melanoma cell lines (Sk-mel 30 and RPMI-7951) served as positive controls for RT-PCR detection of tyrosinase mRNA. Overall patient survival curves were constructed using Kaplan-meier estimates. Results: Tyrosinase mRNA was detected by RT-PCR assay of all four of the established melanoma cell lines tested. Nine of the 64 patients with malignant melanoma were found to have detectable tyrosinase mRNA in their peripheral blood cells (tyrosinase-positive patients). The 16 patients with localized primary melanoma did not have detectable tyrosinase mRNA in their peripheral blood cells. Among the 48 patients with metastatic disease, all 27 patients who exhibited no evidence of disease progression were tyrosinase negative. Notably, all nine tyrosinase-positive patients had visceral metastases and were found to exhibit disease progression at the time of the sampling. Four of the nine tyrosinase-positive patients were also found to test negative at times without evidence of progressive disease; one patient became negative after achieving stable disease and three became positive for tyrosinase transcripts on disease progression. The probability of survival from time of sampling was significantly lower in the nine tyrosinase-positive patients when tested versus the 23 patients with comparable disease but without detectable tyrosinase mRNA (two-sided; P[less than or equal to].05). Conclusions: The results of this study demonstrate that the detection of tyrosinase mRNA in cells in the peripheral blood by RT-PCR may be a useful prognostic marker for predicting tumor progression and poor clinical outcome in patients with malignant melanoma. [J Natl Cancer Inst 1996; 88:590-4]

The hydrogen transfer of furfural to furfuryl alcohol with i-propanol as the hydrogen source over cation-exchanged Lewis acidic BEA zeolite has been investigated by means of density functional calculations. The reaction proceeds in three steps. First the O–H bond of i-propanol is broken to form a propoxide intermediate. After that, the furylmethoxy intermediate is formed via hydrogen transfer process, and finally furylmethoxy abstracts the proton to form the furfuryl alcohol product. The second step is rate-determining by requiring the highest activation energy (23.8 kcal/mol) if the reaction takes place on Li-Sn-BEA zeolite. We find that the catalytic activity of various cation-exchanged Sn-BEA zeolites is in the order Li-Sn-BEA > Na-Sn-BEA > K-Sn-BEA. The lower activation energy for Li-Sn-BEA compared to Na-Sn-BEA and K-Sn-BEA can be explained by the larger charge transfer from the carbonyl bond to the catalyst, leading to its activation and to the attraction of the hydrogen being transferred. The larger charge transfer in turn is due to the smaller gap between the energies of furfural HOMO and the zeolite LUMO in Li-Sn-BEA, compared to both Na-Sn-BEA and K-Sn-BEA. In a similar way, we also compare the catalytic activity of tetravalent metal centers (Sn, Zr, and Hf) substituted into BEA and find in the order Zr ≥ Hf > Sn, based on activation energies. Finally we investigate statistically which property of the reactants is a suitable descriptor for an approximative prediction of the reaction rate in order to be able to quickly screen promising catalytic materials for this reaction.

At the occasion of the Prodex and Swisstech trade shows, the Minister of the Economy for the Jura Canton visited the Jura companies that were exhibiting in Basle and took [...]

The oxidation of CO by N2O over metal–organic framework (MOF) M3(btc)2(M = Fe, Cr, Co, Ni, Cu, and Zn) catalysts that contain coordinatively unsaturated sites has been investigated by means of density functional theory calculations. The reaction proceeds in two steps. First, the N–O bond of N2O is broken to form a metal oxo intermediate. Second, a CO molecule reacts with the oxygen atom of the metal oxo site, forming one C–O bond of CO2. The first step is a rate-determining step for both Cu3(btc)2and Fe3(btc)2, where it requires the highest activation energy (67.3 and 19.6 kcal/mol, respectively). The lower value for the iron compound compared to the copper one can be explained by the larger amount of electron density transferred from the catalytic site to the antibonding of N2O molecules. This, in turn, is due to the smaller gap between the highest occupied molecular orbital (HOMO) of the MOF and the lowest unoccupied molecular orbital (LUMO)  of N2O for Fe3(btc)2compared to Cu3(btc)2. The results indicate the important role of charge transfer for the N–O bond breaking in N2O. We computationally screened other MOF M3(btc)2(M = Cr, Fe, Co, Ni, Cu, and Zn) compounds in this respect and show some relationships between the activation energy and orbital properties like HOMO energies and the spin densities of the metals at the active sites of the MOFs.

The selective oxidation of carbon monoxide (CO) remains a challenge in many research areas. Here we propose using porous hybrid organic–inorganic frameworks as tunable single-metal site catalysts which can be utilized for the oxidation reaction. Low-valent zinc ions were embedded on ZSM-5 zeolite and metal organic framework (MOF) supports to be used as nonprecious metal catalysts. Unlike the case with ionic compensation between the metal and zeolite, linker-functionalized MOFs exhibit a delocalized electron of the metal residing on both the organic linker and the metal atom. This electron delocalization plays a crucial role in the catalytic activity by assisting charge transfer of the metal site to break the O–O bond. By adding electron-donating groups to the linker, we found the activation energy to be dramatically decreased to ∼4 kcal/mol compared with 18 kcal/mol for the zeolite. This is essential for oxidation at low temperature. Moreover, the donating groups result in a more stable Zn active site on the supports. We also show relationships between activation energy and (a) charge, (b) ionization energy of Zn atom, and (c) the highest occupied molecular orbital energy. Those parameters can therefore be related to how well the electron transfer from Zn to the O2molecule proceeds and can be used to construct a model for activation energy prediction which is useful for catalyst design and screening. We believe that such a customizable platform of catalysts could open a new avenue for optimizing both activity and selectivity of catalysts for low-temperature preferential CO oxidation applications.

Electron addition to cobalt tricarbonyl nitrosyl (Co(CO3NO) and its clusters has been explored in helium nanodroplets. Anions were formed by adding electrons with controlled energies, and reaction products were identified by mass spectrometry. Dissociative electron attachment (DEA) to the Co(CO)3NO monomer gave reaction products similar to those reported in earlier gas phase experiments. However, loss of NO was more prevalent than loss of CO, in marked contrast to the gas phase. Since the Co–N bond is significantly stronger than the Co–C bond, this preference for NO loss must be driven by selective reaction dynamics at low temperature. For [Co(CO)3NO]Nclusters, the DEA chemistry is similar to that of the monomer, but the anion yields as a function of electron energy show large differences, with the relatively sharp resonances of the monomer being replaced by broad profiles peaking at much higher electron energies. A third experiment involved DEA of Co(CO)3NO on a C60molecule in an attempt to simulate the effect of a surface. Once again, broad ion yield curves are seen, but CO loss now becomes the most probable reaction channel. The implication of these findings for understanding focused electron beam induced deposition of cobalt is described.

The adsorption of CO2and its hydration to carbonic acid on copper alkoxide functionalized Metal–Organic Frameworks (Cu-MOFs) is studied by density functional theory calculations. The adsorption Gibbs free energies of CO2, H2O and two forms of carbonic acid on Cu-MOFs are −2.4, −14.1, −13.5, and −28.9 kcal/mol, respectively. The preferred adsorption of H2O on the Cu enhances also the stability of the Cu-MOFs against moisture. Two possible pathways are considered for the hydration reaction of CO2. In the first one, the reaction starts with the simultaneous forming of a CO bond and the breaking of an OH bond, leading to a HCO3intermediate. This intermediate then undergoes a hydride-shift and is subsequently protonated to form carbonic acid. The second step is considered to be the rate-determining step of this reaction with an activation energy of 28.2 kcal/mol. In the second pathway, a three-step process is considered. It commences by dissociation of the water OH bond and the formation of a CO bond between the resulting OH species and the incoming CO2molecule. Finally, the hydrogen transfers to the HCO3intermediate to generate carbonic acid. The first step has the highest activation energy, 19.1 kcal/mol, and is therefore rate-determining. Since this is also much lower compared with the first pathway, the second pathway is preferred for the CO2hydration on Cu-MOFs. Without a catalyst, the barrier is much higher, 53.4 kcal/mol, indicating that Cu-MOFs might be a suitable material to adsorb and hydrate CO2.

The transformation of ethanol, one of the low-cost biomass products, into fine chemicals has received considerable attention related to the development of clean industrial technologies. We calculated the reaction mechanism of ethanol dehydrogenation to acetaldehyde over Au-exchanged ZSM-5 zeolite with and without surface oxygen by means of the density functional theory. The reaction is proposed to proceed in two steps. In the first, dissociation of the ethanol O–H bond leads to an ethoxide intermediate which is then converted to acetaldehyde. The reaction barrier for the first step is 9.0 kcal/mol for the Au–O/ZSM-5 zeolite, much smaller than for the Au/ZSM-5 zeolite (43.0 kcal/mol). For step 2, the reaction barriers are 4.4 kcal/mol for Au–O/ZSM-5 and 30.8 kcal/mol for Au/ZSM-5, respectively. The results indicate that the presence of surface oxygen on the Au site assists both the ethanol O–H bond dissociation and the conversion of ethoxide to acetaldehyde.

The dehydrogenated parent anion [M−H]−is one of the most dominant anions formed in dissociative electron attachment to various small biomolecules like nucleobases and single amino acids. In the present study, we investigate the [M−H]−channel for the dipeptide dialanine by utilizing an electron monochromator and a two‐sector‐field mass spectrometer. At electron energies below 2 eV, the measured high‐resolution ion‐efficiency curve has a different shape to that for the single amino acid alanine, which is explained by the altered threshold energies for formation of [M−H]−determined in quantum chemical calculations. Moreover, the structure of the formed [M−H]−anion is further studied by investigating the unimolecular and collision‐induced decay of this anion. Trajectory calculations have been carried out to aid the interpretation of the experimentally observed fragmentation patterns.

The methylation of 2-methylnaphthalene (2-MN) with methanol to the 2,6 (2,6-DMN) and 2,7 (2,7-DMN) dimethylnaphthalenes catalyzed over nanoporous BEA zeolite has been investigated quantum chemically using the M06-2X density functional. The catalytic cycle consists of three elementary steps: (1) formation of a methoxy species from methanol that is bound to a zeolite oxygen atom, (2) methylation of 2-MN to DMN with methoxy leading to naphthalynic carbocations, and (3) formation of DMN by proton back-donation from naphthalynic carbocations. The reaction profiles are similar for both the 2,6 and the 2,7 isomer and are in agreement with the experimental observation that they are produced in equal amounts on acidic BEA zeolite. A possible side reaction, the formation of dimethyl ether via the self-activation of methanol, is also discussed. The stability of the intermediates inside the pores is, to a large extent, governed by the steric constraints and the van der Waals dispersion interactions induced by the pore structure of BEA zeolite. These are the key parameters for understanding the relationship between zeolite topology and catalytic activity.

The adsorption and tautomerization reaction of acetone in H-FER, H-ZSM-5, and H-MCM-22 zeolites has been studied using full quantum calculations at the M06-2X/6-311+G(2df,2p) level of theory. The combination of a large quantum cluster and this meta-hybrid density functional results in reasonably accurate adsorption energies of −26.9, −28.1, and −23.9 kcal/mol for acetone adsorption in H-FER, H-ZSM-5, and H-MCM-22, respectively. Due to the acidity of the zeolite and the framework confinement effect, the tautomerization of acetone proceeds through a much lower activation barrier than in the isolated gas phase or in the presence of water molecules alone. The activation energies are calculated to be 24.9, 20.5, and 16.6 kcal/mol in H-FER, H-ZSM-5 and H-MCM-22, respectively. The endothermic reaction energy decreases with increasing of the zeolite pore sizes and amounts to 22.7, 17.6, and 15.9 kcal/mol for the reaction in H-FER, H-ZSM-5 and H-MCM-22, respectively. In addition, the adsorbed acetone enol is found to be highly unstable in the zeolite framework and readily reverse-transforms to adsorbed acetone with a very small activation energy. The activity trend and relative stabilities of the adsorbed keto and enol forms are well correlated with the interactions within the Brønsted acid site.

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Abstract: The advantages of corrected Marcus plots as compared to the more traditional corrected Tafel plots are discussed and illustrated by the treatment of experimental data. The procedures are proposed to avoid the uncertainties of EDL correction and to estimate the reliable values of transmission coefficient and total reorganization energy. Special emphasis is placed on the diagnostics of activationless reactions in frames of the same method.

Abstract: The induced dipole moment of a water molecule close to a point charge (with the radius of Na+ or Be2+) is computed with the three main methods to implement molecular polarization (point dipoles, fluctuating charges and shell model). The results are compared with high level ab initio calculations and studied as a function of the charge-molecule distance for selected molecular orientations. For the single charge case rather good estimations of the ab initio induced dipole are obtained, with no significant divergences appearing at the shortest distances. Nevertheless, these (linear polarization) methods fail as the charge increases, suggesting that nonlinear effects may not be neglected. Regarding the capabilities of each method, the point dipole method is the one that performs better overall, with the shell model achieving acceptable results in most instances. The fluctuating charge method has some noticeable limitations for implementations with a similar number of interaction sites. [Copyright &y& Elsevier]

Metastable fragmentation of neon dimer ions has been investigated by measuring and analyzing high resolution kinetic energy release distributions. Data were obtained by a modified MIKE mass-analyzed ion kinetic energy scan technique. Due to the high energy resolution it was possible to distinguish two different reaction mechanisms in the μs time regime which produce Neions with different kinetic energy distributions. Theoretical studies based on ab initiocalculations of potential energy curves allowed the assignment of the reactions to specific electronic transitions in the excited Ne2ion. The unusual bimodal kinetic energy release distribution arises from competition between radiative and non radiative decay of the long-lived Ne2II12ustate.

Ab initiocalculations for clusters containing Li+and up to six acetonitrile molecules have been performed by using the B3LYP, MP2(FC) and MP2(Full) methods with the 6-311+G**basis set. The three computational methods give similar results for highly symmetric structures. In the case of MP2 calculation the inclusion of core electrons does not effect the values of the intermolecular distances and binding energy in the Li+-acetonitrile complex. The average ion–ligand distance increases with increasing number of acetonitrile molecules in the cluster. It has been shown that the energy required to incorporate an additional acetonitrile molecule in the Li-acetonitrile clusters containing 5 and 6 acetonitrile molecules is almost equal to the acetonitrile–acetonitrile interaction energy in the most stable acetonitrile dimer and therefore it is very difficult to predict whether the coordination sphere of Li+contains four, five or six acetonitrile molecules. A molecular dynamics simulation has also been performed on LiI-acetonitrile system. The coordination number of the Li+and I−have been found to be 5.97 and 14, respectively. The first solvation shell of Li+has an octahedral geometry; the coordination sphere of the I−ion does not show any special arrangement.

Liquid DMSO has been investigated by means of X-ray and neutron diffraction, quantum-chemical calculations and molecular dynamics MD simulations. A new analytical all-atom pair potential for DMSO–DMSO interactions was developed from quantum-chemical calculations and employed in the simulations. The MD-derived total structure function agrees favourably with those obtained from the X-ray and neutron diffraction experiments. An analysis of the local structure shows a rather unstructured liquid with a slight preference for antiparallel ordering of the S–O dipoles.

A molecular dynamics simulation of a 0.28 molar aqueous AlCl3 solution was performed with the flexible Bopp, Jancsó, and Heinzinger (BJH) model for water and a newly developed three-body potential for Al³⁺–(H2O)2 interactions derived from ab initio calculations. The simulations extended over 25 ps at an average temperature of 300 K. The structural properties of the solution are discussed on the basis of radial distribution functions and the orientation of the water molecules. Dynamical properties and OH frequency shifts were calculated from autocorrelation functions for the hydration shells of the ions. © 2000 John Wiley & Sons, Inc. Int J Quant Chem 80: 892–906, 2000

A photograph is presented of an activist in Zurich, Switzerland wearing a mask of Sepp Blatter, the president of the governing body of the FIFA World Cup Fédération internationale de football association (FIFA).

We report the results of a molecular dynamics simulation on the system KNO3/H2O. For the interaction between nitrate anion, water molecule, and potassium cation, newly developed analytical potentials were employed whereas the water–water interactions were described with the MCYL potential. Water and nitrate anion were treated as flexible molecules. The periodic box contained 341 water molecules, 1 nitrate anion, and 1 potassium cation. The structure of the hydration shell is investigated in terms of radial and angular distribution functions. The vibrational density of states is calculated to derive information about the frequency shifts of the anion upon hydration and of the surrounding water molecules. We compare the findings of our simulations with other molecular dynamics simulations involving nitrate anion and with quantum chemical reaction field calculations. Our simulations show a well-defined but orientationally very flexible hydration shell and small gas-to-liquid frequency shifts for both nitrate anion and hydration shell water molecules. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 805–814, 1999

Hydrated Al³⁺ ions [Al(H2O)n]³⁺, n=1–6, were examined with ab initio self-consistent field (SCF) calculations. The relative contributions of two-, three-, and higher-body terms to the total interaction energy for an [Al(H2O)6]³⁺ complex were calculated. The sum of all three-body contributions amounts to ~30% of the sum of all pair-additive contributions and is opposite in sign. The three-body energy contributions were also derived for two types of [Al(H2O)2]³⁺ complexes. In the first type, both water molecules reside in the first hydration shell of Al³⁺ and in the second type there is one in the first shell and one in the second. Altogether 15,500 triplets were investigated and analytical two- and three-body potential energy functions were derived via a fitting procedure.  ©1999 John Wiley & Sons, Inc. Int J Quant Chem 75: 659–669, 1999

The correlation between intramolecular bond length and vibrational frequency shifts was calculated at the MP4(aug-cc-PVTZ) ab initio level for a number of molecules (LiH, BH, HF, OH⁻, HDO, BF, CN⁻, and HCI) exposed to uniform electric fields in the range from −0.10 to +0.10 au. The “ω vs. re” correlation curves always consist of two branches, each approximately linear. The slopes for the molecules investigated here vary between −2500 and −16600 cm⁻¹/Å. The slopes are well described by an expression containing only the free-molecule second- and third-order force constants and the reduced mass for the stretching mode. Experimental data for polar molecules can be expected to show deviations from a linear “ω vs. re” correlation (i) for molecules where the maximum of the frequency vs. field curve occurs at a positive field and (ii) for molecules where the maximum of the frequency vs. field curve falls on the negative-field side but very close to the zero-field case, and (iii) in bonding situations when there is much electron overlap. As opposed to uniform-field situations, anharmonicity and electronic overlap have a substantial influence on the “frequency vs. re” slopes in molecular environments. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 63: 537–546, 1997

An intermolecular potential function for the magnesium complex of 1,4,7,10-tetraazacyclododecane (cyclen) and water has been derived from ab initio molecular orbital calculations. The form of this interaction function is obtained by fitting 250 points of the calculated energy surface.

The interaction between nitrate anion and water has been investigated by Hartree–Fock calculations with the 6-311+G(d, p) basis set and by B3LYP density functional calculations with the aug-cc-pVTZ basis set. It is found that the global energy minimum is a planar configuration where both hydrogen atoms of water are coordinated to two oxygen atoms of NO3⁻ by distorted hydrogen bonds. In contrast to former studies on NO3⁻/H2O this configuration is found to be asymmetric at the highest theoretical level employed. The corresponding structure with C2v symmetry is a saddle point at slightly higher energy. A singly hydrogen-bonded configuration is still about 2.4 kcal/mol higher in energy. The shifts in the vibrational frequencies of water and nitrate upon complexation were calculated. A compact analytical potential function of NO3⁻/H2O for use in statistical thermodynamic simulations was obtained from 390 points of the energy surface and an intramolecular force field for the nitrate anion is presented. © 1998 John Wiley & Sons, Inc. Int J Quant Chem 70: 877–886, 1998

Hydrated lanthanide(III) ions Ln3 +(H2O)8with Ln3 += La3 +to Yb3+have been studied using ab-initio methods. The binding energy as a function of ion-water distance and position of the ion in the rare earth series is discussed. The calculations are related to recent experimental results elucidating the hydration behaviour of lanthanide(III) ions. Since no S-shape behaviour is found for complex binding energies or metal-oxygen distance, the calculations indicate that observed thermodynamic anomalities should come from hydration number changes due to the different ionic radii within the series.

3-(Diethylphosphono) substituted 1,5-hexadienes are prepared by the α-regioselective allylation of allylic phosphonates. The products can be converted into vinylic phosphonates via two types of reactions. The first involves Cope rearrangement yielding the terminal vinylphosphonates of the 1,5-hexadiene system. The second involves γ-silanylation leading to the formation of the 1-silanyl-3-phosphono derivatives of the 2,5-hexadiene skeleton. Keywords: allylic and vinylic phosphonates, nucleophilicity of allylphosphonate carbanions, electrophilic silanylation, Cope rearrangement of alkenylphosphonates.

The stability constants of magnesium and lithium complexes of 1,4,7,10-tetraazacyclododecane (cyclen) have been determined in 0.5 M KNO 3at 25 °C by means of potentiometric titration, as KMgL= 1.77 × 10 2and KLi L< 10 −2, respectively. Ab initiocalculations on the protonated species of the cyclen ligand have been performed in order to obtain a better understanding of experimental protonation constants, and to compare them to previous calculations on the investigated metal complexes.

Impaired renal function and/or pre-existing atherosclerosis in the deceased donor increase the risk of delayed graft function and impaired long-term renal function in kidney transplant recipients.