Di[2,6-bis(5-phenylpyrazol-3-yl)pyridine]Co(II): an old coordination mode fora novel supramolecular assembly

CoCl2 was treated with 1, 2, and 6 eq. of 2,6-bis(5-phenylpyrazol-3-yl)pyridine (H2L) yielding respectively the monosubstituted [Co(H2L)Cl2], the disubstituted [Co(H2L)2][PF6]2, and a supramolecular assembly formed by a central disubstituted octahedral complex and four more hydrogen bonded peripheral ligands, [{Co(H2L)2}(H2L)4][PF6]2, as illustrated by X-ray crystal structure analysis

Multifunctional hybrid materials based on transparent poly(methyl methacrylate) reinforced by lanthanoid hydroxo clusters

Three pentanuclear lanthanoid hydroxo clusters of composition [Ln(OH)5(abzm)10], where Ln = Eu, Tb,Ho and abzm = di(4-allyloxy)benzoylmethanide, have been prepared. The structures have beencharacterised by means of IR, Raman, elemental analyses and X-ray diffraction, showing a pyramidalsquare-based cluster core. The clusters (Tb and Ho) exhibit Curie?Weiss Law behaviour, displayingantiferromagnetic ordering at low temperatures. The emission properties of the Eu cluster demonstratethe abzm- ligand is an efficient antenna (lex = 420 nm) only for the sensitisation of Eu luminescence inthe visible range, via energy transfer to the 5D0 state of the trivalent metal. The clusters have beenreacted in the presence of methyl methacrylate and azobisisobutyronitrile to prepare reinforcedpolymers via radical polymerisation. The obtained materials exhibit swelling upon immersion intoorganic solvents up to 110% of their original size, in agreement with the presence of cluster-crosslinked polymeric chains. Also, no loss of transparency was observed in the preparation of the materials. The characteristic red emission of the Eu cluster in also retained in the polymeric material

Magnetic energy-barrier distributions for ferrihydrite nanoparticles formed by reconstituting ferritin

The spherical cage-like protein ferritin was reconstituted with varying numbers of iron atoms perprotein shell ranging from approximately 20 to 1100 at temperatures of both 25 and 50 C toproduce ironIII oxyhydroxide ferrihydrite particles with different average particle sizes anddegrees of crystallinity. After characterization of the structural properties of the resultingiron-oxyhydroxide nanoparticles with transmission electron microscopy and M?auerspectroscopy, magnetic viscosity measurements were made in zero applied magnetic field and theresulting data were used to calculate the apparent magnetic-moment-weighted energy barrierdistributions for the samples. The distributions measured were typically comprised of both alognormal distribution and an exponential decay of barrier frequency with increasing barrier height.Evidence that the lognormal component of this distribution arises from the distribution of particlevolumes and moments within the ensemble is strongly supported by the increase in the mode of theenergy barrier distribution with increasing particle size. The exponentially decaying distribution hasa relatively higher contribution to the overall distribution for the more crystalline reconstitutedferritin samples suggesting that it may be associated predominantly with uncompensated spins atparticle surfaces