Anne Spasojević-de Biré

Evidence Based on Crystal Structures and Calculations of a C−H···π Interaction Between an Organic Moiety and a Chelate Ring in Transition Metal Complexes

Structural and computational evidence is given for a special type of C−H···π interaction where the C−H group interacts with the π-system of a six-membered chelate ring. An investigation of crystal structures shows that these interactions take place in quite a number of metal complexes, including organometallic compounds; in the CSD we found over 1200 structures with these interactions. These interactions exist in complexes of different metals and various chelate rings. DFT calculations on three model systems show that the energy of these interactions is about 1 kcal/mol. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Mixed ligand Co(II), Ni(II) and Cu(II) complexes containing terephthalato ligands. Crystal structures of diaqua(2,2′-dipyridylamine)(terephthalato)metal(II) trihydrates (metal=cobalt or nickel)

Abstract A series of nine ternary Co(II), Ni(II) and Cu(II) complexes with some aromatic diamines and dianion of terephthalic acid (tpht) have been synthesized and characterized by elemental analysis, magnetic susceptibility measurements, IR and diffuse-reflectance spectroscopy. All compounds were obtained as microcrystalline solids, stable in air and insoluble in common solvents. Two of them, [M(tpht)(dipya)(H 2 O) 2 ]·3H 2 O [M=Co(II), Ni(II); dipya=2,2′-dipyridylamine], were obtained as single crystals and their crystal structures have been determined by X-ray structure analysis. Both structures consist of discrete [M(tpht)(dipya)(H 2 O) 2 ] 2+ complex units with two H 2 O molecules in the trans position. Three additional H 2 O molecules together with coordinated H 2 O and O atoms from COO groups make a three-dimensional network of hydrogen bonds. Terephthalato ligands are coordinated by only one COO group, which acts as a chelating ligand. Central metal ions are in a distorted octahedral environment. Based on the above-mentioned analysis and known crystal structures, the possible structures and geometry of the complexes are discussed. All Co(II) and Ni(II) complexes are pseudooctahedral and mononuclear, with only one of the tpht COO groups coordinated in a chelate mode. Cu(II) complexes have probably distorted octahedral geometry with bridging role of tpht ions and monodentate or strongly asymmetric coordination of COO groups.

Electronic Properties of a Cytosine Decavanadate: Toward a Better Understanding of Chemical and Biological Properties of Decavanadates

We have synthesized and crystallized a cytosine-decavanadate compound, Na(3) [V(10)O(28)] (C(4)N(3)OH(5))(3)(C(4)N(3)OH(6))(3).10H(2)O, and its crystal structure has been determined from a single-crystal X-ray diffraction. A high resolution X-ray diffraction experiment at 210 K (in P1 space group phase) was carried out. The data were refined using a pseudo-atom multipole model to get the electron density and the electrostatic properties of the decavanadate-cytosine complex. Static deformation density maps and Atoms in Molecules (AIM) topological analysis were used for this purpose. To get insight into the reactivity of the decavanadate anion, we have determined the atomic net charges and the molecular electrostatic potential. Special attention was paid to the hydrogen bonding occurring in the solid state between the decavanadate anion and its environment. The comparison of the experimental electronic characteristics of the decavanadate anions to those found in literature reveals that this anion is a rigid entity conserving its intrinsic properties. This is of particular importance for the future investigations of the biological activities of the decavanadate anion.

Transition metal complexes with thiosemicarbazide-based ligands. Part XLI. Two crystal structures of cobalt(III) complexes with salicylaldehyde S-methylisothiosemicarbazone and theoretical study on orientations of coordinated pyridines

Abstract Two compounds, [CoIII(L)(py)3][CoII(py)Cl3]·EtOH and [CoIII(L)(py)3]I3 (H2L=salicylaldehyde S-methylisothiosemicarbazone, py=pyridine), were synthesized and the crystal structures determined by single-crystal X-ray diffraction. In both structures the geometries of the cation are very similar to a thiosemicarbazide-based ligand coordinated in the mer configuration. The axial pyridines are in mutual perpendicular orientation, the angles between the planes being 85.3(2) and 82.5(2)°. The plane of the equatorial pyridine is tilted with respect to the equatorial plane by about 40°. The orientations of the pyridines were studied in model systems by quantum chemistry calculations. It was shown that the interactions between axial and equatorial pyridines are responsible for the orientation of pyridines in the complex cation; consequently, there are very similar geometries of the complex cation in both crystal structures. The compounds were also characterized by elemental analysis, molar conductivity, magnetic susceptibility and electronic absorption spectra.

Molecular reactivity of busulfan through its experimental electrostatic properties in the solid state.

AbstractPurpose. In the route of developing novel liquid phase formulations based on the encapsulation of busulfan into liposomes in nontoxic solvents, drug crystallization inevitably occurs. In order to better understand the reactivity of busulfan, the characterization of its molecular properties was therefore considered as a key point. Also, preliminary attempts to prevent crystallization using cyclodextrins were explored. Methods. An accurate single-crystal high-resolution X-ray diffraction experiment at 100 K has been carried out. The experimental electron density of busulfan was refined using a multipole model. Busulfan/β-cyclodextrin coprecipitates were analyzed by powder X-ray diffraction and 1H-NMR spectroscopy. Results. The electrostatic properties of busulfan and the methylsulfonate fragment dipole moment (3.2 D) were determined. The polar moieties play a key role in the crystallization of busulfan, which presents a nucleophilic region surrounding the sulfonate part, whereas the carbon chain displays an electrophilic character. This highlights the subtle busulfan/β-cyclodextrin association. Conclusions. Busulfan electrostatic properties were used to quantify its chemical reactivity. This explains the difficulty to formulate busulfan into liposomes due to a strong polar character of the methylsulfonate terminal groups. The complexation with cyclodextrins deserves to be further investigated to allow the formulation of busulfan in nontoxic solvents.

SYNTHESIS AND X-RAY CRYSTAL ANALYSIS OF [Cu2(HCOO)tpmc]-[Cu2(CH3COO)tpmc](ClO4)6·6H2O(tpmc = N,N′,N″,N‴-TETRAKIS-(2-PYRIDYLMETHYL)-1,4,8,11-TETRAAZACYCLOTETRADECANE). PREPARATION AND CHARACTERIZATION OF [Cu2(HCOO)tpmc](ClO4)3·H2O

The new structure of [Cu2(HCOO)tpmc][Cu2(CH3COO)tpmc](ClO4)6·6H2O (tpmc = N,N′,N″,N‴-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetra-decane), consists of [Cu2(HCOO)tpmc]3+ and [Cu2(CH3COO)tpmc]3+ cations, perchlorate anions and water of crystallization. Two different binuclear transition metal complexes with the tpmc ligand form the same crystal lattice giving the monocrystals. The crystal structure of this compound has been solved by single crystal X-ray diffraction studies. It crystallizes in the triclinic system, space group with a = 14.176(3), Å, b = 16.864(4) Å, c = 20.681(3), Å, α = 100.68(3)○, β = 101.00(3)○, γ = 101.37(3)○, V = 4628.6(16), Å3, R = 0.0729. Each copper atom is penta-coordinated in a distorted square-pyramidal arrangement. In addition, [Cu2(HCOO)tpmc](ClO4)3·H2O was prepared and its properties were compared with the previously described μ-acetato analogue.

A new experimental setup for high-throughput controlled non-photochemical laser-induced nucleation: application to glycine crystallization

Non-photochemical laser-induced nucleation (NPLIN) has been a growing field of study since 1996, and more than 40 compounds including organics, inorganics and proteins have now been probed under various conditions (solvents, laser types, laser beams etc.). The potential advantages of using this technique are significant, in particular polymorphic control. To realize these benefits, the objective is a carefully designed experimental setup and highly controlled parameters, for example temperature and energy density, in order to reduce the uncertainty regarding the origin of nucleation. In this paper, a new experimental setup designed to study NPLIN is reported. After a full technical description of the present setup, the different functionalities of this device will be illustrated through results on glycine. Glycine crystals obtained through NPLIN nucleate at the meniscus and exhibit different morphologies. The nucleation efficiency, as a function of the supersaturation of the solution used and the laser beam energy density, has also been established for a large number of samples, with all other parameters held constant.

Chemical bonding in methylidyne complexes: neutron diffraction study on a single crystal of BrWCH(dmpe-d12)2

Carbyne complexes have been extensively studied but only a few of them contain the MC–H moiety (M = transition metal). In order to contribute to the debate about the linearity of this fragment, two neutron diffraction experiments on single crystal have been performed at 100 and 293 K on the trans-W(CH)(dmpe)2Br (dmpe = 1,2-bis(dimethylphosphino)ethane) (1). The results point, without ambiguity, to the linearity of the fragment. The specific behaviour of the dmpe ligand is modelled and interpreted.

Neutron diffraction study on a single crystal of pentacarbonyldiethylcyanamidechromium at 110 K

The crystal structure of the complex [Cr(NCNEt2)(CO)5] has been determined by neutron diffraction at 110 K. The crystal used was twinned and the twin law was analysed. The structure is composed of layers of molecules parallel to the twin plane which are held together by van der Waals interactions and intermolecular hydrogen bonds. The cyanamide ligand has an intermediate σ-donor:π-acceptor ratio, stronger, for example, than the carbene ligand. There are two types of cis-carbonyl groups in the structure, resulting from the conjugation effect of the cyanamide skeleton in the molecule. Charge transfer, which is characteristic of the delocalization of the lone pair of the amino nitrogen along the six-atom linear chain, is observed along the bonds on the binary molecular axis, including the trans-carbonyl group.

Chemical bonding in metalaheterocumulene complexes: II Demonstration of a temperature dependant conformational disorder of the methyl groups in [(CO)5CrNCN(C2H5)2]☆

During the determination of the crystal structure of [(CO)5CrNCN(C2H5)2] by neutron diffraction, a remarkable te temperature-dependance of the intensity of three reference reflections between 100 and 300 K was accidentally observed. In order to try to understand the nature of this phenomenon, the behaviour of this compound as a function of the temperature has been studied by differential calorimetry, and by power and single crystal X-ray diffraction methods. These experiments show neither a phase transition nor a crystal space group modification. The experimental results, supported by a simplified model, suggest a rotational disorder of the methyl groups near room temperature.