Structural characterization of the regioisomers of di(hydroxybutyl) ether by GC‐EI MS and theoretical calculations

Di(hydroxybutyl) ether (DHBE), a liver protecting drug, is composed of a mixture of three regioisomers: 4‐(3‐hydroxybutoxy)‐2‐butanol (1), 3‐(4‐hydroxy‐2‐butoxy)‐1‐butanol (2), and 3‐(3‐hydroxybutoxy)‐1‐butanol (3). Unequivocal differentiation of each regioisomer of DHBE was rapidly obtained without isolation of the single components, using GC‐MS with electron ionization (EI). The mass spectrum of 1 showed a rearrangement ion at m/z 118, characteristic of the 3‐hydroxybutyl chain, deriving from loss of acetaldehyde from the molecular ion, whereas 2 and 3 were characterized by the ion at m/z 117, expected from α‐cleavage of the 4‐hydroxy‐2‐butyl chain. The species at m/z 118, in turn, loses a water molecule via a mechanism involving both alcohol hydrogens, as shown by deuterium exchange experiments. Both this finding and theoretical calculations support a mechanism in which the loss of acetaldehyde in 1 occurs via a cyclic intermediate, stabilized by a strong hydrogen bond between the alcohol oxygen bearing the charge and the other alcohol oxygen, and involves initial hydrogen transfer from the former to the latter. The EI spectrum of 2, having two 4‐hydroxy‐2‐butyl chains, showed the fragmentations expected from classical fragmentation rules of aliphatic ethers and alcohols, whereas the EI spectrum of 3, bearing one 4‐hydroxy‐2‐butyl and one 3‐hydroxybutyl chain, showed essentially the characteristic fragments of both chains. Copyright © 2009 John Wiley & Sons, Ltd.     

Activation of Hydrogen by Palladium(0): Formation of the Mononuclear Dihydride Complex trans‐[Pd(H)2(IPr)(PCy3)]

An even split : In sharp contrast with the general behavior of Pd⁰ complexes, [Pd(IPr)(PCy₃)] is able to activate the H? H bond. The resulting trans‐[Pd(H)₂(IPr)(PCy₃)] is the first isolated mononuclear dihydride palladium compound. Its formation is supported by multinuclear NMR spectroscopy, density functional calculations, and X‐ray diffraction studies. The stability and reactivity of this new species are examined.

     

Isolation and Hydrogenation of a Complex with a Terminal Iridium–Nitrido Bond

An N for Ir : The synthesis and X‐ray crystal structure of a late‐transition‐metal complex with a terminal nitrido ligand and its hydrogenation to the related amido complex are reported (see scheme).

     

Molecular and electronic structures of oxo-bis(benzene-1,2-dithiolato)chromate(V) monoanions. A combined experimental and density functional study

Two oxo-bis(benzene-1,2-dithiolato)chromate(V) complexes, namely, [CrO(L(Bu))2]1- and [CrO(L(Me))2]1-, have been synthesized and studied by UV-vis, EPR, magnetic circular dichroism (MCD), and X-ray absorption spectroscopy and by X-ray crystallography; their electro- and magnetochemistries are reported. H2L(Bu) represents the pro-ligand 3,5-di-tert-butylbenzene-1,2-dithiol, and H2L(Me) is the corresponding 4-methyl-benzene-1,2-dithiol. A structural feature of interest for both the complexes is the folding of the dithiolate ligands about the S-S vector providing Cs symmetry to the complexes. Geometry optimizations using all-electron density functional theory with scalar relativistic corrections at the second-order Douglas-Kroll-Hess (DKH2) and zeroth-order regular approximation (ZORA) levels result in excellent agreement with the experimentally determined structures and electronic and S K-edge X-ray absorption spectra. From DFT calculations, the Cs instead of C2v symmetry for the complexes is attributed to the strong S(3p) --> Cr(3d(x2-y2)) pi-donation in Cs geometry providing additional stability to the complexes.     

Pressure-induced sequential magnetic pole inversion and antiferromagnetic-ferromagnetic crossover in a trimetallic prussian blue analogue

The flexibility of the structure of Prussian blue analogues and its ability to incorporate a variety of competing magnetic interactions have allowed the design of mixed ferro-ferrimagnets, which span the whole spectrum of magnetic behavior, including the rare phenomenon of magnetization reversal in response to a change in temperature. Hydrostatic pressure is used here to induce multiple reversals of the direction of the spontaneous magnetization in the trimetallic Prussian blue analogue, Rb0.64Ni0.31Mn0.87[Fe(CN)6].2.8H2O. Remarkably, the magnetic response is extremely sensitive to pressure, and the magnetization flips from positive to negative and back to positive in a very narrow pressure range (0 < P < 0.6 kbar). A further increase in pressure to 4.0 kbar induces an internal redox reaction, and the magnetic order switches from ferrimagnetic to bulk ferromagnetism.     

X-ray illumination induced Fe(II) spin crossover in the Prussian blue analogue cesium iron hexacyanochromate

The effect of X-ray illumination on the structural properties of the mixed valence Prussian blue analogue CsFe(II)[Cr(III)(CN)6] has been studied by time-dependent high-resolution synchrotron X-ray diffraction. Abrupt isosymmetric phase transitions, accompanied by dramatic volume collapse, were found in the temperature range 245-265 K, induced by sudden Fe(II) spin transitions from the high spin (HS) (4t(2g)2e(g), S = 2) to the low spin (LS) (6t(2g)0e(g), S = 0) configuration. Absorption of X-ray photons generates photoexcited Fe(II)(LS) domains whose size rapidly grows with time until the percolation threshold is reached and the structure collapse is triggered. The persistent character of the optically excited spin crossover states derives from the strong electron-phonon coupling, associated with the large lattice relaxations, which accompany the internal spin rearrangements. It is thus possible to use X-ray light in a controllable and efficient way to induce photoswitching between the ground and hidden or inaccessible excited states in suitably selected multistable materials in the bulk.     

Site-specific conjugation of ScFvs antibodies to nanoparticles by bioorthogonal strain-promoted alkyne-nitrone cycloaddition

Particularly suitable: An N-terminal serine mutant of anti-HER2 scFv antibody was conjugated to polymer-coated magnetofluorescent nanoparticles by strain-promoted alkyne-nitrone cycloaddition. The resulting nanoparticles (see scheme) proved effective in targeting and labeling HER2-positive breast cancer cells.     

Hole transfer dynamics from dye molecules to p-type NiO nanoparticles: effects of processing conditions

Hole transfer dynamics of Atto647N sensitized p-type NiO nanoparticle (NP) thin films is investigated using both ensemble-averaged and single-molecule spectroscopy techniques. The rate of hole transfer is dependent on the processing conditions and is enhanced when the NiO is pre-annealed in air as compared to vacuum. This is possibly due to an upward shift of the valence band of the semiconductor and an increase in the free energy for hole transfer as more Ni(2)O(3) are formed in the presence of air. The stretched exponential fluorescence decay profile of Atto647N on NiO NP suggests the presence of a distribution of hole transfer rates. This is in agreement with the observed emission lifetime and intensity fluctuations and non-monoexponential fluorescence decays for individual Atto647N molecules on NiO NP films. A plausible explanation for the heterogeneous hole transfer rates is an inhomogeneous distribution of (defect) sites on the metal oxide due to the processing conditions and a fluctuation in the intermolecular interaction.     

Dinuclear Pt(II)-bisphosphonate complexes: a scaffold for multinuclear or different oxidation state platinum drugs

Geminal bisphosphonates (BPs), used in the clinic for the treatment of hypercalcaemia and skeletal metastases, have been also exploited for promoting the specific accumulation of platinum antitumor drugs in bone tissue. In this work, the platinum dinuclear complex [{Pt(en)}(2)(μ-AHBP-H(2))](+) (1) (the carbon atom bridging the two phosphorous atoms carrying a 2-ammonioethyl and a hydroxyl group, AHBP-H(2)) has been used as scaffold for the synthesis of a Pt(II) trinuclear complex, [{Pt(en)}(3)(μ-AHBP)](+) (2), and a Pt(IV) adamantane-shaped dinuclear complex featuring an oxo-bridge, [{Pt(IV)(en)Cl}(2)(μ-O)(μ-AHBP-H(2))](+) (3) (X-ray structure). Compound 2 undergoes a reversible, pH dependent, rearrangement with a neat switch point around pH = 5.4. Compound 3 undergoes a one-step electrochemical reduction at E(pc) = -0.84 V affording compound 1. Such a potential is far lower than that of glutathione (-0.24 V), nevertheless compound 3 can undergo chemical reduction to 1 by GSH, most probably through a different (inner-sphere) mechanism. In vitro cytotoxicity of the new compounds, tested against murine glioma (C6) and human cervix (HeLa) and hepatoma (HepG2) cell lines, has shown that, while the Pt(IV) dimer 3 is inactive up to a concentration of 50 μM, the two Pt(II) polynuclear compounds 1 and 2 have a cytotoxicity comparable to that of cisplatin with the trinuclear complex 2 generally more active than the dinuclear complex 1.