A Simple and Efficient Mechanochemical Route for the Synthesis of Salophen Ligands and of the Corresponding Zn, Ni, and Pd Complexes.

A number of salophen ligands and their Zn, Ni, and Pd complexes were synthesized by an efficient one-pot mechanosynthesis protocol. The reaction products were characterized by means of complementary solid-state techniques, i.e., powder X-ray diffraction, single-crystal X-ray diffraction, and solid-state NMR spectroscopy. Four new crystal structures of metal salophen complexes as DMSO solvates are here reported. The described simple and relatively fast (about 1 h for all derivatives) procedure is a good alternative to classical methods performed in organic solvents.

In situ diffraction study of catalytic hydrogenation of VO2: stable phases and origins of metallicity.

Controlling electronic population through chemical doping is one way to tip the balance between competing phases in materials with strong electronic correlations. Vanadium dioxide exhibits a first-order phase transition at around 338 K between a high-temperature, tetragonal, metallic state (T) and a low-temperature, monoclinic, insulating state (M1), driven by electron-electron and electron-lattice interactions. Intercalation of VO2 with atomic hydrogen has been demonstrated, with evidence that this doping suppresses the transition. However, the detailed effects of intercalated H on the crystal and electronic structure of the resulting hydride have not been previously reported. Here we present synchrotron and neutron diffraction studies of this material system, mapping out the structural phase diagram as a function of temperature and hydrogen content. In addition to the original T and M1 phases, we find two orthorhombic phases, O1 and O2, which are stabilized at higher hydrogen content. We present density functional calculations that confirm the metallicity of these states and discuss the physical basis by which hydrogen stabilizes conducting phases, in the context of the metal-insulator transition.

A new structure of a serotonin salt: comparison and conformational analysis of all known serotonin complexes.

Four serotonin salt structures (serotonin adipate, C10H13N2O(+)·C6H9O4(-), is a previously unknown structure) were analysed to understand the influence of the anion on serotonin conformation. Hydrogen bonding alone favours a flat conformation, whereas additional stacking interactions between ions may possibly account for the nonplanar conformation. Since molecular conformation, stability and biological activity are interrelated, one can consider influencing the chemical and biological properties of serotonin by selecting an appropriate counter-ion for salt formation.

X-ray diffraction and Raman study of DL-alanine at high pressure: revision of phase transitions.

The effect of pressure on DL-alanine has been studied by X-ray powder diffraction (up to 8.3 GPa), single-crystal X-ray diffraction and Raman spectroscopy (up to ~6 GPa). No structural phase transitions have been observed. At ~1.5-2 GPa, cell parameters b and c become accidentally equal to each other, but the space-group symmetry does not change. There is no phase transition between 1.7 and 2.3 GPa, contrary to what has been reported earlier [Belo et al. (2010). Vibr. Spectrosc. 54, 107-111]. The presence of the second phase transition, which was claimed to appear within the pressure range from 6.0 to 7.3 GPa (Belo et al., 2010), is also argued. The changes in the Raman spectra have been shown to be continuous in all the pressure ranges studied.

Two new structures in the glycine-oxalic acid system.

Glycinium semi-oxalate-II, C(2)H(6)NO(2)(+).C(2)HO(4)(-), (A), and diglycinium oxalate methanol disolvate, 2C(2)H(6)NO(2)(+).C(2)O(4)(2-).2CH(3)OH, (B), are new examples in the glycine-oxalic acid family. (A) is a new polymorph of the known glycinium semi-oxalate salt, (C). Compounds (A) and (C) have a similar packing of the semi-oxalate monoanions with respect to the glycinium cations, but in (A) the two glycinium cations and the two semi-oxalate anions in the asymmetric unit are non-equivalent, and the binding of the glycinium cations to each other is radically different. Based on this difference, one can expect that, although the two forms grow concomitantly from the same batch, a transformation between (A) and (C) in the solid state should be difficult. In (B), two glycinium cations and an oxalate anion, which sits across a centre of inversion, are linked via strong short O-H...O hydrogen bonds to form the main structural fragment, similar to that in diglycinium oxalate, (D). Methanol solvent molecules are embedded between the glycinium cations of neighbouring fragments. These fragments form a three-dimensional network via N-H...O hydrogen bonds. Salts (B) and (D) can be obtained from the same solution by, respectively, slow or rapid antisolvent crystallization.

Tribenzoatobismuth(III): a new -polymorph.

A new polymorph (ß) was obtained for an active pharmaceutical ingredient, bis-muth tribenzoate, [Bi(C(6)H(5)CO(2))(3)]. The new ß-polymorph is 1.05 times denser than the previously known polymorph [Rae et al. (1998 ▶). Acta Cryst. B54, 438-442]. In the ß-polymorph, the Bi atom is linked with three benzoate anions, each of them acting as a bidentate ligand, and these assemblies with C(3) point symmetry can be considered as 'mol-ecules'. The structure of the ß-polymorph has no polymeric chains, in contrast to the previously known polymorph. The 'mol-ecules' in the ß-polymorph are stacked along [001], so that the phenyl rings of the neighbouring mol-ecules are parallel to each other. Based on the pronounced difference in the crystal structures, one can suppose that two polymorphs should differ in the dissolution kinetics and bioavailability.

Phase transitions in the crystals of L- and DL-cysteine on cooling: the role of the hydrogen-bond distortions and the side-chain motions. 2. DL-cysteine.

Structural strain and a first-order phase transition in the crystalline DL-cysteine on cooling and on reverse heating were followed by Raman spectroscopy and X-ray diffraction. The transition is reversible and has a large hysteresis (over 100 K). The temperature at which the transition is observed depends strongly on the cooling/heating rate. The phase transition is accompanied by crystal fragmentation. The low-temperature phase could be obtained not only as a result of the solid-state transformation in situ as a polycrystalline sample (with strong preferred orientation, or without it, depending on the preparative technique), but also (using an original crystallization technique) as a single crystal of the quality suitable for structural analysis. For the first time, the crystal structure of the low-temperature phase was solved independently by powder and by single-crystal diffraction techniques. The spectral changes were correlated with the precise diffraction data on the intramolecular conformations and the intermolecular hydrogen bonding before and after the phase transition. The role of the distortion of the intermolecular hydrogen bonds and of the motions of the -CH(2)SH side chains in the phase transition is discussed in a comparison with the low-temperature phase transition in L-cysteine, which is of a different type and preserves the single crystals intact (Kolesov et al. J. Phys. Chem. B, 2008, 112 (40), 12827-12839).

Solid Aluminum Borohydrides for Prospective Hydrogen Storage.

Metal borohydrides are intensively researched as high-capacity hydrogen storage materials. Aluminum is a cheap, light, and abundant element and Al3+ can serve as a template for reversible dehydrogenation. However, Al(BH4 )3 , containing 16.9 wt % of hydrogen, has a low boiling point, is explosive on air and has poor storage stability. A new family of mixed-cation borohydrides M[Al(BH4 )4 ], which are all solid under ambient conditions, show diverse thermal decomposition behaviors: Al(BH4 )3 is released for M=Li+ or Na+ , whereas heavier derivatives evolve hydrogen and diborane. NH4 [Al(BH4 )4 ], containing both protic and hydridic hydrogen, has the lowest decomposition temperature of 35 °C and yields Al(BH4 )3 ⋅NHBH and hydrogen. The decomposition temperatures, correlated with the cations' ionic potential, show that M[Al(BH4 )4 ] species are in the most practical stability window. This family of solids, with convenient and versatile properties, puts aluminum borohydride chemistry in the mainstream of hydrogen storage research, for example, for the development of reactive hydride composites with increased hydrogen content.

Hydrazine selective dual signaling chemodosimetric probe in physiological conditions and its application in live cells.

A rhodamine-cyanobenzene conjugate, (E)-4-((2-(3',6'-bis(diethylamino)-3-oxospiro[isoindoline-1,9'-xanthene]-2-yl)ethylimino)methyl)benzonitrile (1), which structure has been elucidated by single crystal X-ray diffraction, was synthesized for selective fluorescent "turn-on" and colorimetric recognition of hydrazine at physiological pH 7.4. It was established that 1 detects hydrazine up to 58 nM. The probe is useful for the detection of intracellular hydrazine in the human breast cancer cells MCF-7 using a fluorescence microscope. Spirolactam ring opening of 1, followed by its hydrolysis, was established as a probable mechanism for the selective sensing of hydrazine.

Anion-induced Ag(I) self-assemblies with electron deficient aromatic ligands: anion-π-system interactions as a driving force for templated coordination networks.

Three novel 1D, 2D and 3D coordination polymers were successfully isolated using nitrogen based 3,6-bis(2'-pyrimidyl)-1,2,4,5-tetrazine (BPymTz) and 2,4,6-tris(2-pyrimidyl)-1,3,5-triazine (TPymT) ligands with Ag(I) ions. The formation of these supramolecular assemblies was templated through anion-π-system interactions.

Challenges in the synthetic routes to Mn(BH4)2: insight into intermediate compounds.

We have studied the reaction of MnCl2 with MBH4 (M = Li(+), Na(+), K(+)) in Et2O. Crystal structures of two new intermediates, named [{M(Et2O)2}Mn2(BH4)5] (M = Li(+), Na(+)), were elucidated by X-ray diffraction. Mn(BH4)2 in a mixture with LiBH4 or NaBH4 forms upon the solvent removal in a vacuum. [{M(Et2O)2}Mn2(BH4)5] contains 2D layers formed by Mn and BH4 groups, linked through the alkali metal atoms coordinated to Et2O. The loss of the solvent molecules leads to the segregation of the partially amorphous or nanocrystalline LiBH4/NaBH4 and a creation of the 3D framework of the crystalline Mn(BH4)2. While using LiBH4 led to Mn(BH4)2 contaminated with LiCl, presumably due to an efficient trapping of the latter salt by the [Mn(BH4)2-Et2O] system, the reaction with NaBH4 produced chlorine-free Mn(BH4)2 accompanied with NaBH4. Using KBH4 led to the formation of K2Mn(BH4)4 as a second phase. Two pyridine-containing solvomorphs, [Mn(py)3(BH4)2] and [Mn(py)4(BH4)2]·2py, were isolated in pure form. However, Mn(BH4)2 partly decomposes upon removal of pyridine molecules.

First structurally characterized self-assembly of bipodal N-thiophosphorylated bis-thiourea with Co(II): magnetic properties and thermal decomposition.

Reaction of piperazine with isothiocyanate (iPrO)2P(S)NCS leads to N-thiophosphorylated bis-thiourea (iPrO)2P(S)NHC(S)NC4H8NC(S)NHP(S)(OiPr)2 (H2L). Recrystallization of H2L from DMSO leads to the formation of the new ligand (iPrO)2P(S)NC4H8NP(S)(OiPr)2 (1). Reaction of doubly deprotonated L with Co(II) leads to the [Co2L2] complex. The thermal properties of [Co2L2] in an air atmosphere were studied by means of TGA with the observed final residue corresponding to [CoPS3]2. The crystal structure of [Co2L2] was elucidated by single crystal X-ray diffraction. Two metal cations are in a tetrahedral 1,5-S2S'2 environment formed by the C=S and P=S sulfur atoms. Investigation of the temperature dependence of the magnetic susceptibility is consistent with two effectively non-interacting Co(II) S = 3/2 ions.