Topochemical nitridation of SrFeMoO.

The topotactic nitridation of cation ordered, tetragonal Sr2FeMoO6 in NH3 at moderate temperatures leads to cubic, Fm3[combining macron]m double perovskite oxynitride Sr2FeMoO4.9N1.1 where double-exchange interactions determine ferromagnetic order with TC ≈ 100 K.

Energetic, Topological and Electric Field Analyses of Cation-Cation Nucleic Acid Interactions in Watson-Crick Disposition.

A theoretical study of the effect of the diprotonation on the nucleic acid bases (A : U, A : T and G : C) in Watson-Crick conformation has been carried out by means of DFT computational methods in vacuum. In addition, the corresponding neutral and monoprotonated binary complexes have been considered. Most of the diprotonated species studied are stable, even though the binding energy is positive due to the overall repulsive electrostatic term.

Synthesis of Au Nanoparticles Assisted by Linker-Modified TiO Nanoparticles.

Plasmonic nanoparticles, especially gold ones, have been widely employed as photosensitizers in photoelectrovoltaic or photocatalytic systems. To improve the system's performance, a greater interaction of the nanoparticles with the semiconductor, generally TiO, is desired. Moreover, this performance is enhanced when an efficient covering of TiO surface by the sensitizer is achieved.

Topochemical synthesis of cation ordered double perovskite oxynitrides.

Topochemical nitridation in ammonia at moderate temperatures of cation ordered SrFeWO produces new antiferromagnetic double perovskite oxynitrides SrFeWON with 0 < x ≤ 1. Nitrogen introduction induces the oxidation of Fe to Fe and decreases T from 38 K (x = 0) to 13 K for SrFeWON which represents the first example of a double perovskite oxynitride with both high cationic order and nitrogen content. This synthetic approach can be extended to other cation combinations expanding the possibility of new materials in the large group of double perovskites.

Charged versus Neutral Hydrogen-Bonded Complexes: Is There a Difference in the Nature of the Hydrogen Bonds?

A theoretical study on some carboxylic acid dimers formed by positively or negatively charged molecules has been carried out by using DFT methods. The resulting dimers possess either a charge of +2 or -2. In addition, the corresponding neutral complexes have also been considered.

The paradox of hydrogen-bonded anion-anion aggregates in oxoanions: a fundamental electrostatic problem explained in terms of electrophilic···nucleophilic interactions.

A theoretical study of anionic complexes formed by two partly deprotonated oxoacids joined by hydrogen bonds has been carried out at the MP2 computational level. In spite of the ionic repulsion, local energy minima are found both in the gas phase and in aqueous solution. Electrostatic potential and electron density topologies, and the comparison with neutral complexes formed by oxoacids, reveal that the ionization has no significant effect on the properties of the hydrogen bonds.

Crystal structures and DFT calculations of new chlorido-dimethylsulfoxide-M(III) (M = Ir, Ru, Rh) complexes with the N-pyrazolyl pyrimidine donor ligand: kinetic vs. thermodynamic isomers.

New chlorido-dimethylsulfoxide-iridium(III), ruthenium(III) and rhodium(III) complexes with the 2-(1H-pyrazol-1-yl)-pyrimidine (pyrapyr) ligand (OC-6-N1)-[Rh(III)Cl3(DMSO-κS)(pyrapyr)] (1a, N = 3 and 1b, N = 4); (OC-6-N1)-[Ru(III)Cl3(DMSO-κS)(pyrapyr)] (2a, N = 3 and 2b, N = 4) and (OC-6-N1)-[Ir(III)Cl3(DMSO-κS)(pyrapyr)] (3a, N = 3 and 3b, N = 4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction studies (1a, 1b, 2a, 2b, a disordered crystal 3a/3b and a cocrystal 3a·3b). In all cases, the metal centers show octahedral geometry coordinated to three chloride ligands and one S coordinated dimethylsulfoxide (DMSO-κS). The coordination sphere of the metal is completed by the pyrapyr molecule.

Experimental and theoretical studies on the coordination chemistry of the N1-hexyl substituted pyrimidines (uracil, 5-fluorouracil and cytosine).

N(1)-Hexyl substituted pyrimidines were shown to present solubility properties closer to the real bases than the commonly used methyl and ethyl derivatives, yielding bi-layered structures in the solid state. The study of their coordination capabilities, mainly with Ag(I) and Hg(II), is presented in order to prove their reactivity. A series of coordination complexes, namely, [Hg(N(1)-hexyl-5-fluorouracilate)2]4·6H2O (1), (Ag(+))·[Ag(N(1)-hexyl-5-fluorouracilate)2](-) (2), [Ag(NO3)(N(1)-hexyluracil-κO(4))4] (3), [ZnBr2(N(1)-hexylcytosine)2] (4), [CdBr2(N(1)-hexylcytosine)2] (5), [HgBr2(N(1)-hexylcytosine)2] (6) and [CoBr2(N(1)-hexylcytosine)2] (7), have been synthesized in good yields and X-ray characterized.

Synthesis, X-ray characterization and computational studies of Cu(II) complexes of N-pyrazolyl pyrimidine.

In this manuscript we report the synthesis and X-ray characterization of several complexes of Cu(II) with a 2-(1H-pyrazol-1-yl)-pyrimidine (L) ligand. Complexes CuLCl(2) (1), [CuL(2)(H(2)O)(2)](NO(3))(2) (2) and [CuL(2)H(2)O](NO(3))(2) (3) are mononuclear systems and [CuL(NO(3))(2)](n) (4) is polymeric. In the solid state, complexes 2 and 3 are characterized by the presence of anion-π interactions that are relevant for the final 3D architecture and packing.

Electrostatics at the origin of the stability of phosphate-phosphate complexes locked by hydrogen bonds.

Stronger than you'd think: Ab initio calculations reveal that hydrogen bonds can lock phosphates into stable gas-phase complexes, showing that hydrogen bonding can overcome anion-anion repulsion. These complexes present a large energetic barrier of dissociation. The stability of the complexes can be explained in terms of the electrostatic interaction in the hydrogen-bond region.

C-H···X (X = O, N or π) interactions in benzyl carbamate.

The crystal packing and interaction energy of benzyl carbamate, C(8)H(9)NO(2), have been analysed in detail by the PIXEL method. Benzyl carbamate forms layers of hydrogen-bonded molecules, with the layers connected by weaker C-H..

Tuning the interaction energy of hydrogen bonds: the effect of the substituent.

The effect of the substituent R in the hydrogen bonding properties of FH···FR (R = H, Al, Li, Cl and CCH) complexes has been studied by theoretical calculations. The dependency of the interaction energy with the hydrogen bond distance and R is explained in terms of the topologies of the electron density and the electrostatic potential. A simple model of the hydrogen bond interaction energy, which can be assimilated to an interaction potential, is defined in terms of a stabilizing mutual polarization of the monomers and an overall destabilizing contribution associated with the electron density reorganization when the overlap of the closed shells is large enough.

Universal features of the electron density distribution in hydrogen-bonding regions: a comprehensive study involving H...X (X=H, C, N, O, F, S, Cl, pi) interactions.

Topological analyses of the theoretically calculated electron densities for a large set of 163 hydrogen-bonded complexes show that HX interactions can be classified in families according to X (X=atom or pi orbital). Each family is characterised by a set of intrinsic dependencies between the topological and energetic properties of the electron density at the hydrogen-bond critical point, as well as between each of them and the bonding distance. Comparing different atom-acceptor families, these dependencies are classified as a function of the van der Waals radius r(X) or the electronegativity chi(X), which can be explained in terms of the molecular orbitals involved in the interaction.

Effect of an external electric field on the dissociation energy and the electron density properties: The case of the hydrogen bonded dimer HF...HF.

The effect of a homogeneous external electric field parallel to the hydrogen bond in the FH...

Zero-flux surfaces of the electrostatic potential: the border of influence zones of nucleophilic and electrophilic sites in crystalline environment.

The topology of the electrostatic potential varphi(r) has been studied for single molecules using geometries and electron distributions rho(r) determined from high-resolution single-crystal X-ray diffraction data. The electrostatic potential gradient nablavarphi(r), which is the negative of the electric field E = -nablavarphi, has been represented, revealing the position of zero-flux surfaces and critical points. Local maxima and minima of the electrostatic potential are interpreted in terms of electrophilic and nucleophilic sites, which present influence zones delimited by zero-flux surfaces containing saddle points.

Synthesis and investigation of the boron cluster anion [7-(2'-pyridyl)-7,8-nido-dicarbaundecaborate] and its protonated form.

The structurally chiral [7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)](-), [](-), anion was prepared by a partial degradation reaction of 1-(2'-pyridyl)-1,2-closo-C(2)B(10)H(11). From this anion a protonated specie, H[7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)] , and a tetramethylammonium salt, [NMe(4)][7-(2'-pyridyl)-7,8-nido-C(2)B(9)H(11)], [NMe(4)][] can be obtained. The (1)H{(11)B} DNMR study on in the temperature range from 298 to 203 K identified the weakly basic nitrogen atom in the pyridine ring as the proton accepting site in solid state and low temperature and revealed pronounced weakening of the nitrogen-proton interaction while the temperature increases.

Topological properties of the electrostatic potential in weak and moderate N...H hydrogen bonds.

The topological analyses of the electrostatic potential phi(r) and the electron density distribution rho(r) have been performed for a set of 20 neutral complexes with weak and moderate N...

Contributions to the application of the transferability principle and the multipolar modeling of H atoms: electron-density study of L-histidinium dihydrogen orthophosphate orthophosphoric acid. I.

The electron density of L-histidinium dihydrogen orthophosphate orthophosphoric acid has been determined from X-ray and neutron diffraction data at low temperature (120 K). Topological analysis of the electron density has been used to analyse the effect of the multipolar refinement strategy on the electron-density model in the hydrogen-bonding regions. The electron density at low temperature has also been used to acquire high-quality experimental thermal parameters at room temperature using the transferability principle.

Topological analysis of the electron density distribution in perturbed systems. I. Effect of charge on the bond properties of hydrogen fluoride.

Within the framework of the molecular orbital (MO) theory, the addition of one electron to the 4sigma antibonding orbital of the neutral (F...

Magneto-structural correlations in binuclear copper(II) compounds bridged by a ferrocenecarboxylato(-1) and an hydroxo- or methoxo-ligands.

The syntheses, characterization and X-ray crystal structures of the first two examples of asymmetrically bridged dinuclear copper(ii) complexes containing a ferrocenecarboxylato ligand and a methoxo group in [{Cu(dmen)}2(micro-OMe){micro-O2C(eta5-C5H4)Fe(eta5-C5H5)}](ClO4)2, 1, (dmen=N,N-dimethylethylenediamine) or an hydroxo group in [{Cu(tmen)}2(micro-OH){micro-O2C(eta5-C5H4)Fe(eta5-C5H5)}](ClO4)2, 2 , (tmen=N,N,N'N'-tetramethylethylenediamine) are reported. Magneto-chemical studies revealed that 1 and 2 exhibit opposite superexchange interactions between the two Cu(II) paramagnetic centers: an antiferromagnetic coupling (J = -11 cm(-1)) in 1 and a ferromagnetic interaction (J = +29 cm(-1)) in 2. The results obtained from these studies suggest that the weak interactions between the Cu(II) ions and the perchlorate anions detected in the crystal structures are important to introduce significant distortions in the heterobridged [Cu2(micro-OR){micro-O2C(eta5-C5H4)Fe(eta5-C5H5)}]2+ cores of 1 and 2, which clearly affect the nature and strength of the superexchange interactions.

Preparation, solid-state characterization, and computational study of a crown ether attached to a squaramide.

[structure: see text] Crystals of a disecondary squaramide covalently linked to a crown ether presents a great variety of inter- and intramolecular nonbonded interactions including C-H/pi contacts, C-H...

The modulating possibilities of dicarbollide clusters: optimizing the Kharasch catalysts.

exo-Cluster dicarbollides substitution has allowed tuning of the E degrees (Ru(II)/Ru(III)) potential to obtain the best-performing Kharasch catalyst. We postulate that this is possible through the to-and-fro electron movement between the boron cluster and the sulfonium moieties.

Synthesis, structure and nuclease properties of several ternary copper(II) peptide complexes with 1,10-phenanthroline.

Three new ternary peptide-Cu(II)-1,10-phenanthroline (phen) complexes, [Cu(L-ala-gly)(phen)].3.5H(2)O 1, [Cu(L-val-gly)(phen)] 2 and [Cu(gly-L-trp)(phen)].

Comparison of electron density properties in frozen and relaxed electronic distributions.

Two kinds of electron densities for several small molecules (H(2), FH, CH(3)CH(3), CH(3)NH(2), CH(3)OH, and CH(3)F) have been generated for a wide range of bond distances. The first one, as the sum of the electron density of the isolated fragments, and the second one by optimizing the electron density at each given geometrical disposition. A number of properties of this two electronic distributions have been compared (position of the bond critical points, electron density, Laplacian, curvatures, and local energies).

A comparative analysis of mono- and disaccharide benzyl fucopyranosides.

The syntheses and X-ray analyses of two fucopyranosides, the monosaccharide benzyl 3,4-di-O-acetyl-2-hydroxy-beta-D-fucopyranoside, C(17)H(22)O(7), and the disaccharide 1-benzyl O-(2,3-di-O-acetyl-4,6-O-benzylidene-beta-D-glucopyranosyl)-(1-->2)-3,4-O-isopropylidene-beta-D-fucopyranoside, C(33)H(40)O(12), are described. The different substituents induce small conformational changes on the fucopyranoside ring. However, the conformation of the benzyl group varies from (+)gauche for the monosaccharide to synperiplanar for the disaccharide.