The 3d‐metal mediated nitrene transfer is under intense scrutiny due to its potential as an atom economic and ecologically benign way for the directed amination of (un)functionalised C−H bonds. Here ...we present the isolation and characterisation of a rare, trigonal imido cobalt(III) complex, which bears a rather long cobalt–imido bond. It can cleanly cleave strong C−H bonds with a bond dissociation energy of up to 92 kcal mol−1 in an intermolecular fashion, unprecedented for imido cobalt complexes. This resulted in the amido cobalt(II) complex Co(hmds)2(NHtBu)−. Kinetic studies on this reaction revealed an H atom transfer mechanism. Remarkably, the cobalt(II) amide itself is capable of mediating H atom ion or stepwise proton/electron transfer depending on the substrate. A cobalt‐mediated catalytic application for substrate dehydrogenation using an organo azide is presented.
An concept: A trigonal planar imido cobalt(III) complex, obtained from reaction of a quasi‐linear cobalt(I) complex with an organo azide, is capable of intermolecular H atom ion of C−H bonds. The resulting cobalt(II) amide itself can either deprotonate the substrate, facilitate an H atom ion or mediate a stepwise proton/electron transfer. As the latter regenerates the starting cobalt(I) complex, a first catalytic application is presented.
Nanocomposite patterns and nanotemplates are generated by a single‐step bottom‐up concept that introduces laser‐induced periodic surface structures (LIPSS) as a tool for site‐specific reaction ...control in multicomponent systems. Periodic intensity fluctuations of this photothermal stimulus inflict spatial‐selective reorganizations, dewetting scenarios and phase segregations, thus creating regular patterns of anisotropic physicochemical properties that feature attractive optical, electrical, magnetic, and catalytic properties.
Quasi-linear anionic 3d-metal(I) silylamides are a new and promising class of molecules. Due to their highly negative reduction potential we wanted to test their capability to reduce substrates under ...coordination of their monoanionic radicaloid form. In a proof of principle study, we present the results of the reaction of metal(I) silylamides of chromium to cobalt with 2,2′-bipyridine (bipy), the redox non-innocence and reducibility of which was already established. In the course of these studies complexes of the type K{18-crown-6}M(hmds)2(bipy) (hmds = –N(SiMe3)2) were obtained. These compounds were isolated and thoroughly characterized to confirm the electron transfer onto the bipyridine ligand, which now acts as a radical monoanion. For comparison of the structural changes of the bipyridine ligand, the analogous zinc complexes were also synthesized. Overall our results indicate that anionic metal(I) silylamides are capable of reducing and ligate substrates, even when the electrochemical reduction potential of the latter is by up to 1 V higher.
The redox reactions of various lanthanide metals with 3-(4-pyridyl)pyrazole (4-PyPzH) or 3-(3-pyridyl)pyrazole (3-PyPzH) ligands yield the 2D network ∞2Eu(4-PyPz)2(Py)2 containing divalent europium, ...the 3D frameworks ∞3Ln(4-PyPz)3 and ∞3Ln(3-PyPz)3 for trivalent cerium, praseodymium, neodymium, holmium, erbium, and thulium as well as ∞3La(4-PyPz)3, and the 2D networks ∞2Ln(4-PyPz)3(Py) for trivalent cerium and thulium and ∞2Ln2(4-PyPz)6·Py for trivalent ytterbium and lutetium. The 18 lanthanide coordination polymers were synthesized under solvothermal conditions in pyridine (Py), partly acting as a co-ligand for some networks. The compounds exhibit a variety of luminescence properties, including metal-centered 4f–4f/5d–4f emission in the visible and near-infrared spectral range, metal-to-ligand energy transfer, and ligand-centered fluorescence and phosphorescence. The anionic ligands 3-PyPz− and 4-PyPz− serve as suitable antennas for lanthanide-based luminescence in the visible and near-infrared range through effective sensitization followed by emission through intra–4f transitions of the trivalent thulium, holmium, praseodymium, erbium, and neodymium. ∞2Ce(4-PyPz)3(Py), ∞3Ce(4-PyPz)3, and ∞3Ce(3-PyPz)3 exhibit strong degrees of reduction in the 5d excited states that differ in intensity compared to the ligand-based emission, resulting in a distinct emission ranging from pink to orange. The direct current magnetic studies show magnetic isolation of the lanthanide centers in the crystal lattice of ∞3Ln(3-PyPz)3, Ln = Dy, Ho, and Er.
Superparamagnetic polymer nanofibers intended for drug delivery and therapy are considered here. Magnetite (Fe3O4) nanoparticles in the diameter range of 5-10 nm were synthesized in aqueous solution. ...Polymer nanofibers containing magnetite nanoparticles were prepared from commercially available poly(hydroxyethyl methacrylate), PHEMA, and poly-L-lactide (PLLA) by the electrospinning technique. Nanofibers with diameters ranging from 50 to 300 nm were obtained. Nanofibers containing up to 35 wt % magnetite nanoparticles displayed superparamagnetism at room temperature. The blocking temperature was about 50 K for an applied field of 500 Oe, and the saturation magnetization was 3.5 emu g(-1) and 1.1 emu g(-1) for Fe3O4/PHEMA and Fe3O4/PLLA nanofibers, respectively, and depended on the amount of Fe3O4 nanoparticles in the nanocomposites. To test such magnetic nano-objects for applications as drug carriers and drug-release systems we incorporated a fluorescent albumin with dog fluorescein isothiocyanate (ADFI).
The compound NaFeGe
2
O
6
was grown synthetically as polycrystalline powder and as large single crystals suitable for X-ray and neutron-diffraction experiments to clarify the low temperature ...evolution of secondary structural parameters and to determine the low temperature magnetic spins structure. NaFeGe
2
O
6
is isotypic to the clinopyroxene-type compound aegirine and adopts the typical H
T
-
C
2/
c
clinopyroxene structure down to 2.5 K. The Na-bearing M2 polyhedra were identified to show the largest volume expansion between 2.5 K and room temperature, while the GeO
4
tetrahedra behave as stiff units. Magnetic susceptibility measurements show a broad maximum around 33 K, which marks the onset of low-dimensional magnetic ordering. Below 12 K NaFeGe
2
O
6
transforms to an incommensurately modulated magnetic spin state, with
k
= 0.323, 1.0, 0.080 and a helical order of spins within the M1-chains of FeO
6
octahedra. This is determined by neutron-diffraction experiments on a single crystal. Comparison of NaFeGe
2
O
6
with NaFeSi
2
O
6
is given and it is shown that the magnetic ordering in the latter compound, aegirine, also is complex and is best described by two different spin states, a commensurate one with
C
2′/
c
′ symmetry and an incommensurate one, best being described by a spin density wave, oriented within the (1 0 1) plane.
CoGeO
3
was synthesized at 1,273 and 1,448 K using ceramic sintering techniques in the monoclinic and orthorhombic modification, respectively. The two compounds were analysed by magnetic ...susceptibility measurements and neutron diffraction in order to study magnetic ordering and spin structures at low temperature. The monoclinic form of CoGeO
3
has
C
2/
c
symmetry and orders magnetically below 36 K with a small negative paramagnetic Curie temperature
θ
P
= −4.6 (2) K. The magnetic structure can be described with
k
= (1, 0, 0) in the magnetic space group
C
2′/
c
′ having a ferromagnetic spin arrangement within the chains of M1 sites, but a dominating antiferromagnetic coupling between the chains. At the M1 sites the magnetic spins are aligned within the
a–c
plane forming an angle of 120° with the +
a
-axis and they are not parallel to the spins at M2. Here spins are also ferromagnetically coupled within, but antiferromagnetically coupled between the M1/M2 site bands. The orthorhombic phase of CoGeO
3
displays
Pbca
symmetry and transforms to an antiferromagnetically ordered state
θ
P
= −18.6(2) K below 33 K. The magnetic spin structure can be described with
k
= (0, 0, 0) in space group
Pbca
′ and it is similar to the one of the
C
2/
c
phase except that it is non-collinear in nature, i.e. there are components of the magnetic moment along all three crystallographic axes. Small magneto-elastic coupling is observed in the orthorhombic phase.
Magnetic iron oxide nanoparticles have found application as contrast agents for magnetic resonance imaging (MRI) and as switchable drug delivery vehicles. Their stabilization as colloidal carriers ...remains a challenge. The potential of poly(ethylene imine)-g-poly(ethylene glycol) (PEGPEI) as stabilizer for iron oxide (γ-Fe2O3) nanoparticles was studied in comparison to branched poly(ethylene imine) (PEI). Carrier systems consisting of γ-Fe2O3–PEI and γ-Fe2O3–PEGPEI were prepared and characterized regarding their physicochemical properties including magnetic resonance relaxometry. Colloidal stability of the formulations was tested in several media and cytotoxic effects in adenocarcinomic epithelial cells were investigated.
Synthesized γ-Fe2O3 cores showed superparamagnetism and high degree of crystallinity. Diameters of polymer-coated nanoparticles γ-Fe2O3–PEI and γ-Fe2O3–PEGPEI were found to be 38.7±1.0nm and 40.4±1.6nm, respectively. No aggregation tendency was observable for γ-Fe2O3–PEGPEI over 12h even in high ionic strength media. Furthermore, IC50 values were significantly increased by more than 10-fold when compared to γ-Fe2O3–PEI. Formulations exhibited r2 relaxivities of high numerical value, namely around 160mM−1s−1.
In summary, novel carrier systems composed of γ-Fe2O3–PEGPEI meet key quality requirements rendering them promising for biomedical applications, e.g. as MRI contrast agents.
H3ONbF6 was obtained from the controlled hydrolysis of NbF5 in anhydrous liquid HF. It adopts a polar, orthorhombic crystal structure with space group Iba2 (no. 45, oI88) at room temperature. A ...first‐order phase transition at 137 K leads to a cubic non‐centrosymmetric polymorph in space group I213 (no. 199, cI88). This low‐temperature modification results from a distinct rotation of the H3O+ cations canceling their polar orientation in the room temperature phase. Quantum‐chemical calculations estimate a rotational barrier between 5.8 to 6.4 kJ/mol. At a temperature of 363 K, the compound adopts a centrosymmetric, cubic crystal structure in space group Pm
3‾
${\bar{3}}$
m (no. 221, cP11) that shows rotational disorder of cations and anions. The transition from the polar phase at room temperature to the centrosymmetric phase at high temperature not only reveals the plastic nature of the high‐temperature structure but also hints at potential ferroelectric properties, underscoring the multifaceted behavior of H3ONbF6 across different temperature regimes.
H3ONbF6 was synthesized and characterized. At room temperature, it adopts a polar structure with the dipole momentum of the H3O+ ions directed along the polar axis. A phase transition at 363 K leads to a plastic high‐temperature polymorph hinting towards potential ferroelectric properties of the compound as the H3O+ and NbF6− ions are able to rotate freely. A second phase transition at 137 K leads to a cubic non‐centrosymmetric low‐temperature polymorph.
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