Real-time monitoring of the mechanism of poorly crystalline apatite cement conversion in the presence of chitosan, simulated body fluid and human blood

In this study, the real-time monitoring of structural changes, occurring upon poorly crystalline apatite bone cement hardening in the presence of chitosan, simulated body fluid and human blood, was performed. Strong experimental evidence of octacalcium phosphate intermediate phase is provided. The energy dispersive X-ray diffraction was applied in situ to monitor the structural changes upon the transformation process, while the Fourier transform infrared spectroscopy and the scanning electron microscopy supplied information on the vibrational and morphological properties of the system. The cooperative action of chitosan and simulated body fluid induces the formation of a preferentially oriented hydroxyapatite phase, this process being similar to the oriented self-assembling process in collagen-apatite matrix in human plasma, occurring upon in vivo biomineralization. Conversely, the presence of blood does not induce any significant change in hardening kinetics and the final structure of the investigated cement.     

Laboratory detection of protonated SO2 in two isomeric forms

By means of Fabry-Pérot Fourier transform microwave spectroscopy, the rotational spectrum of protonated sulfur dioxide in two distinct isomeric forms, a cis- and a trans-geometry, is reported. The search for both isomers was based on theoretical structures obtained at the CCSD(T)/cc-pwCVQZ level of theory corrected for zero-point vibrational effects. At a similarly high level of theory, the cis-isomer is calculated to be the global minimum on the potential energy surface, but the trans-isomer is predicted to lie only a few kcal/mol higher in energy. A total of seven lines, including a- and b-type transitions, has been observed for both isomers, and precise rotational constants have been derived. Because sulfur dioxide, SO(2), is a widespread and very abundant astronomical species, and because it possesses a large proton affinity, HOSO(+) is an excellent candidate for radioastronomical detection.     

Modulated perturbation theory for molecular interactions

Modulated Murrell-Shaw-Musher-Amos perturbation theory is used in second order to calculate the interaction energy between two ground-state hydrogen atoms in the region of intermediate internuclear separations from 0 to 6 bohr. Using a small set of variationally optimized two-electron functions accounting for the majority of induction and for spherical and dipole contributions to dispersion, fairly accurate results are obtained for the interaction over the whole range of distances including the united atom. A marked reduction in the induction energy is observed in short range when second-order exchange is introduced.     

Some new routes for the preparation of 3-amino-2-phenyl-4(1H)-quinolinones from anthranilamides

[reaction: see text] Several new routes for the preparation of 3-amino-2-phenyl-4-1(H)-quinolinone 7a are compared. The most efficient is based on the cyclization of phenacyl anthranilamide 2a in the presence of (poly)phosphoric acid. The mechanisms of the rearrangements involved are discussed on the basis of the structures of isolated heterocyclic intermediates. The best methodology for the preparation of the title compound 7a was verified, and 10 other quinolinones 7 were prepared.     

Rhenium(V) and technetium(V) nitrido complexes with mixed tridentate π-donor and monodentate π-acceptor ligands

Mixed-ligand [M(N)(SNS)(PPh(3))] complexes (M = Tc, Re) (1, 2) were prepared by reaction of the precursor [M(N)Cl(2)(PPh(3))(2)] with ligand 2,2'-dimercaptodiethylamine [H(2)SNS = NH(CH(2)CH(2)SH)(2)] in refluxing dichloromethane/ethanol mixtures. In these compounds, 2,2'-dimercaptodiethylamine acts as a dianionic tridentate chelating ligand bound to the [M≡N](2+) group through the two π-donor deprotonated sulfur atoms and the protonated amine nitrogen atom. Triphenylphosphine completes the coordination sphere, acting as a monodentate ligand. [M(N)(NS(2))(PPh(3))] complexes can assume two different isomeric forms depending on the syn and anti orientations of the hydrogen atom bound to the central nitrogen atom of the SNS ligand with respect to the M≡N moiety. X-ray crystallography of the syn isomer of complex 2 demonstrated that it has a distorted trigonal bipyramidal geometry with the nitrido group and the two sulfur atoms defining the equatorial plane, the phosphorus atom of the monophosphine and the protonated amine nitrogen of the tridentate ligand spanning the two reciprocal trans positions along the axis perpendicular to the trigonal plane. Synthesis of the analogous Tc derivatives with tris(2-cyanoethyl)phosphine, [Tc(N)(SNS)(PCN)] [(PCN = P(CH(2)CH(2)CN)(3)], required the preliminary preparation of the new precursor [Tc(N)(PCN)(2)Cl(2)](2) (3), which was prepared by reacting [n-NBu(4)][Tc(N)Cl(4)] with a high excess of PCN. The crystal structure of compound 3 consists of a noncrystallographic centrosymmetric dimer of Tc(V) nitrido complexes having an octahedral geometry. In this arrangement, the apical positions are occupied by two tris(2-cyanoethyl)phosphine groups and the equatorial positions by the nitrido group whereas the two Cl(-) anions and one cyano ligand belong to the other octahedral component of the dimer. By reacting the new precursor [Tc(N)(PCN)(2)Cl(2)](2) with the ligand H(2)SNS the complex [Tc(N)(SNS)(PCN)] (5) was finally obtained in acetonitrile solution. The new Tc(III) complex trans-[Tc(PCN)(2)Cl(4)][n-NBu(4)] (4) was also isolated from the reaction solution used for preparing complex 3 as side product and characterized by X-ray diffraction. The crystal structure of 4 consists of independent trans-[TcCl(4)(PCN)(2)](-) anions situated on crystallographic centers of symmetry and tetrabutylammonium cations in general positions.     

Cosmological expansion and local systems: a Lemaître–Tolman–Bondi model

We propose a Lemaître–Tolman–Bondi system mimicking a two-body system to address the problem of the cosmological expansion versus local dynamics. This system is strongly bound but participates in the cosmic expansion and is exactly comoving with the cosmic substratum.     

An X-Ray Crystallographic Study of the Novel Aminal bis-(<Emphasis Type="Italic">p</Emphasis>-Ethoxycarbonylphenylamino-)methane

Abstract  The crystal structure of bis-(p-Ethoxycarbonylphenylamino-)methane (1) has been determined by single crystal X-ray diffraction analysis. The bis-aminal (1) molecule is V-shaped and situated on a twofold axis passing through C1 with the phenyl rings forming a dihedral angle of 70.2(1)°. The carboxylate and phenyl groups are coplanar. The crystal structure of 1 is compared with the structure of the closely related aminals, 2–5. Crystal data: 1 C₁₉H₂₂N₂O₄, tetragonal, space group I4 ₁ cd (N.110), a = 20.4760(7) Ǻ, b = 20.4760(7) Ǻ, c = 8.2984(3) ?, and V = 3477.7(2) ?³, for Ζ = 8. Index Abstract  The crystal structure of bis-(p-ethoxycarbonylphenylamino-)methane (1) has been determined by single crystal X-ray diffraction analysis.      

An X-Ray Crystallographic Study of Five Compounds from a Series of 1,x-<Emphasis Type="Italic">bis</Emphasis>-(4-Oxo-3,4-dihydro-1,2,3-benzotriazin-3-yl)alkanes

Abstract  

The crystal structures of a series of bis-(4-oxo-3,4-dihydro-1,2,3-benzotriazin-3-yl)alkanes, compounds 5 to 9, have been determined by single crystal X-ray diffraction analysis. The structural parameters of the triazinone rings in the five compounds do not display systematic differences with respect to those reported for a few analogous compounds. The benzotriazinone rings in 5 and 9 are almost perpendicular to the alkylic chain. The molecules in the crystal packing are linked by means of a weak C–H···X H-bond (X = N/O). Compound 6 has two independent molecules in the asymmetric unit; one of the molecules displays disorder within the benzotriazinone moiety linked in position 1 to the propane alkylic group. The disordered molecule displays two conformations of the benzotriazinone linked in position 1 to the propane bridge. Compound 8 also displays disorder within the benzotriazinone moiety linked in position 1 to the pentane alkylic spacer group. The molecules of compound 7, in the crystal packing, also form intra and inter-molecular C–H···X (X = N/O) hydrogen bonds. None of these compounds show any tendency to adopt a folded conformation with intramolecular π–π stacking between benzotriazinone units. Crystal data: 5 C₁₆H₁₂N₆O_2, monoclinic, space group P2 ₁ /c, a = 4.8370(2)?, b = 14.7845(7)?, c = 10.0837(4)?, β = 95.430(2)°, V = 717.88(6)?³, for Ζ = 2; 6 C₁₇H₁₄N₆O_2, triclinic, space group P-1, a = 7.4237(4)?, b = 14.4738(9)?, c = 15.0359(10)?, α = 91.871(3)°, β = 92.147(3)°, γ = 101.233(3)°, V = 1582.2(2)?³, for Ζ = 4; 7 C₁₈H₁₆N₆O_2, monoclinic, space group C2/c, a = 33.8886(10)?, b = 6.4593(2)?, c = 16.0608(6)?, β = 102.298(1)°, V = 3435.0(2)?³, for Ζ = 8; 8 C₁₉H₁₈N₆O_2, triclinic, space group P-1, a = 7.2592(2)?, b = 7.6795(2)?, c = 16.1003(5)?, α = 85.292(1)°, β = 81.367(1)°, γ = 88.377(1)°, V = 884.26(4)?³, for Ζ = 2; 9 C₂₀H₂₀N₆O_2, monoclinic, space group P2 ₁ /c, a = 7.2668(2)?, b = 4.5612(1)?, c = 28.1993(12)?, β = 97.313(2)°, V = 927.07(5)?³, for Ζ = 2.     

A facile “one pot” synthesis of 2,9-disubstituted 8-azapurin-6-ones (3,5-disubstituted 7-hydroxy-3H-1,2,3-triazolo[4,5-d]pyrimidines)

A series of title compounds have been synthesized by utilising benzylazide, cyanoacetamide, ethyl or methyl esters of aliphatic or aromatic carboxylic acids and sodium ethoxide as catalyst.     

Justification de la méthode fonctionnelle pour les courbes gauches

Sans résumé (1) Le contenu de cet article représente le thèse de Doctorat de l'auteur. Pendant sa préparation l'auteur a été boursier du Consiglio Nazionale delle Ricerche (I) et ensuite du Ministero della Pubblica Istruzione (I). Je remercie mes parents pour leur soutien constant.