New BEDT-TTF/[Fe(C5O5)3]3- hybrid system: synthesis, crystal structure, and physical properties of a chirality-induced alpha phase and a novel magnetic molecular metal

The paramagnetic and chiral anion [Fe(C5O5)3]3- (C5O52-=croconate) has been combined with the organic donor BEDT-TTF (=ET=bis(ethylenedithio)tetrathiafulvalene) to synthesize a novel paramagnetic semiconductor with the first chirality-induced alpha phase, alpha-(BEDT-TTF)5[Fe(C5O5)3].5H2O (1), and one of the few known paramagnetic molecular metals, beta-(BEDT-TTF)5[Fe(C5O5)3].C6H5CN (2). Both compounds present layers of BEDT-TTF molecules, with the alpha or beta packing modes, alternating with layers containing the high-spin S=5/2 Fe(III) anions and solvent molecules. In the alpha phase, the alternation of the chiral [Fe(C5O5)3]3- anions along the direction perpendicular to the BEDT-TTF chains induces an alternation of the tilt angle of the BEDT-TTF molecules, giving rise to the observed alpha phase. The alpha phase presents a semiconductor behavior with a high room-temperature conductivity (6 S.cm-1) and an activation energy of 116 meV. The beta phase presents a metallic behavior down to ca. 120 K, where a charge localization takes place with a reentrance to the metallic state below ca. 20 K followed by a metal-semiconductor transition at ca. 10 K. The magnetic properties are dominated by the paramagnetic S=5/2 [Fe(C5O5)3]3- anion with an extra Pauli-type paramagnetism in the metallic beta phase. The ESR spectra confirm the presence of the high-spin Fe(III)-containing anion and show a progressive localization in the organic sublattice along with an antiferromagnetic coupling below ca. 120 K that, in the metallic beta phase, could be at the origin of the transition from the metallic to the activated conductivity regime. The correlation between crystal structure and conductivity behavior has been studied by means of tight-binding band structure calculations which provide a rationalization of the charge distribution and conductivity results.     

Rich pseudopolymorphic behavior of the tetranuclear [Ni4(dpyatriz)2(NO3)8] complex

Reaction of nickel(II) nitrate with the dpyatriz ligand, namely 2,4,6-tris(bis(pyridin-2-yl)amino)-1,3,5-triazine, in acetonitrile produces a tetranuclear NiII coordination compound, [Ni4(dpyatriz)2(NO3)8(CH3CN)2(H2O)2].2CH3CN (1), the crystal structure of which has been determined by X-ray diffraction using a synchrotron source. 1 has been characterized by IR and UV-vis spectroscopy, elemental and thermogravimetric analyses, and magnetic susceptibility measurements. Its solid-state structure exhibits remarkable anion...pi interactions between coordinated nitrate ions and the triazine rings. In addition, a thorough X-ray powder diffraction study has revealed a number of pseudopolymorphic phases (2-5), resulting from various degrees of hydration/solvation of the [Ni4(dpyatriz)2] core. The interconversion scheme among the different phases has been determined using controlled heating, and the basic structural features of the different pseudopolymorphs have been assessed through ab initio powder diffraction methods.     

Self-assembly of beta-cyclodextrin in water. 2. Electron spin resonance

The interaction of amphipilic spin labels with beta-cyclodextrin was investigated using conventional electron spin resonance (ESR) spectroscopy to explore the aggregation of cyclodextrins in water. Methyl 5-doxylstearate (5-DMS) and stearic acid spin probes (n-DSA), which contain a cyclic nitroxide moiety with unpaired electrons covalently linked to the aliphatic chain carbon in positions 5, 7, 12, and 16, show that different dynamic domains coexist in beta-CD water solutions above 3 mM. The results are consistent with the formation of beta-CD self-assembled structures in water above a critical aggregation concentration and confirm the previous findings that were reported in the part 1 article of this series.     

Towards new ligands of nuclear receptors. Discovery of malaitasterol A, an unique bis-secosterol from marine sponge Theonella swinhoei

Malaitasterol A, an unprecedented bis-secosterol, was isolated from a Solomon collection of Theonella swinhoei. The structure was elucidated on the basis of a combination of comprehensive 1D and 2D NMR analysis, high-resolution mass spectrometry and DFT (13)C chemical shift calculations. The biological characterization of malaitasterol A provided evidence that this compound is a potent agonist of pregnane-X-receptor and its putative binding mode to PXR has been obtained through docking calculations.     

Solomonamides A and B, new anti-inflammatory peptides from Theonella swinhoei

Two unprecedented cyclic peptides, solomonamides A and B, were isolated from the marine sponge Theonella swinhoei. The structures were elucidated on the basis of comprehensive 1D and 2D NMR analysis and high-resolution mass spectrometry. A combined approach, involving Marfey's method, QM J based analysis, and DFT J/(13)C calculations, was used for establishing the absolute configuration of the entire molecule. Solomonamide A showed in vivo anti-inflammatory activity.     

Electronic stabilization of trigonal bipyramidal clusters: the role of the Sn(II) ions in [Pt5(CO)5{Cl2Sn(μ-OR)SnCl2}3]3- (R = H, Me, Et, iPr)

The new [Pt(5)(CO)(5){Cl(2)Sn(μ-OR)SnCl(2)}(3)](3-) (R = H, Me, Et, (i)Pr; 1-4) clusters contain trigonal bipyramidal (TBP) Pt(5)(CO)(5) cores, as certified by the X-ray structures of [Na(CH(3)CN)(5)][NBu(4)](2)[1]·2CH(3)CN and [PPh(4)](3)[4]·3CH(3)COCH(3). The TBP geometry, which is rare for group 10 metals, is supported by an unprecedented interpenetration with a nonbonded trigonal prism of tin atoms. By capping all the Pt(3) faces, the Sn(II) lone pairs account for both Sn-Pt and Pt-Pt bonding, as indicated by DFT and topological wave function studies. In the TBP interactions, the metals use their vacant s and p orbitals using the electrons provided by Sn atoms, hence mimicking the electronic picture of main group analogues, which obey the Wade's rule. Other metal TBP clusters with the same total electron count (TEC) of 72 are different because the skeletal bonding is largely contributed by d-d interactions (e.g., [Os(5)(CO)(14)(PR(3))(μ-H)(n)](n-2), n = 0, 1, 2). In 1-4, fully occupied d shells at the Pt(ax) atoms exert a residual nucleophilicity toward the adjacent main group Sn(II) ions permitting their hypervalency through unsual metal donation.     

Pro-porous coordination polymers of the 1,4-bis((3,5-dimethyl-1H-pyrazol-4-yl)-methyl)benzene ligand with late transition metals

Solvothermal reactions of the flexible, pyrazole-based 1,4-bis((3,5-dimethyl-1H-pyrazol-4-yl)methyl)benzene ligand (H(2)BDMPX) with late transition metal ions allowed the isolation of the four coordination compounds M(x)(BDMPX) (x = 1 for M = Zn, 1; Co, 2; Cd, 3; x = 2 for M = Cu, 4). The investigation of the thermal behavior assessed the high thermal robustness of these materials, which are stable in air at least up to 300 °C, with the Cd(II) derivative starting to decompose only around 500 °C. As retrieved by ab initio X-ray powder diffraction, the isomorphous compounds 1-3 possess a dense 3-D network featuring rhombic motifs hinged about rigid and parallel chains of tetrahedral MN(4) chromophores. As demonstrated by thermodiffractometric measurements, temperature increase triggers framework flexibility. The latter is at work also when N(2) adsorption is assayed at 77 K: 1 and 2 show permanent porosity, with BET and Langmuir specific surface areas of 515, 667 m(2)/g and 209, 384 m(2)/g, respectively. 1 and 2 thus represent an intriguing example of "porosity without pores", their pro-porous nature being explained in terms of the flexibility of the rhombic motifs, stimulated by the gas probe and facilitated by the nature of the ligand.     

Resveratrol in Solid Lipid Nanoparticles

This article investigates the possibility of producing solid lipid nanoparticles (SLN) as protective vehicle of resveratrol, an antioxidant characterized by a fast trans-cis isomerization. SLN aqueous dispersions were produced by hot melt homogenization technique and characterized. It was found that the presence of tetradecyl-γ-cyclodextrin in SLN formulation induced an improvement of nanoparticle characteristics. Moreover, a significant reduction in resveratrol photodegradation was noted when the molecule was entrapped in SLN which became more pronounced in the presence of tetradecyl-γ-cyclodextrin. A notable in vitro porcine skin accumulation and an increased antioxidative efficacy were observed by entrapping resveratrol in nanoparticles.     

Application Relevant Characterization of Aqueous Silica Nanodispersions

This work describes the application relevant characterization of eight commercially available silica powders dependent on dispersing procedure using different instruments: photon correlation spectroscopy, nitrogen adsorption, and particle charge detector. The particle size of silica was found to be different in dispersion from that of all types of fumed silica, where, after proper dispersion, the measured average particle size is similar and much higher than the primary particle size. The different properties of these two silica types will be discussed.