No abstract

Large metal-oxo clusters consistently assume spherical or regular polyhedral morphologies rather than high-aspect-ratio structures. Access to elongated core structures has now been achieved by the reaction of lanthanoid salts with a tetrazole-functionalized calixarene in the presence of a simple carboxylate co-ligand. The resulting Ln19 and Ln12 clusters are constructed from apex-fused Ln5O6 trigonal bipyramids and are formed consistently under a range of reaction conditions and reagent ratios. Altering the carboxylate co-ligand structure reliably controls the cluster length, giving access to a new class of rod-like clusters of variable length.

Extension of previous work on the lanthanide(III) ion complexes of p-tert-butyltetrathiacalix [4]arene has led to a variety of structurally characterised species containing oxo-, hydroxo-and aqua-ligands presumably derived from water present in the preparative medium, along with the thiacalixarene in various stages of deprotonation. The overall stoichiometry of some species is remarkably complicated due to the presence of simple anions and multiple solvents. Simplest is the binuclear complex [(µ-H 2 O){Ln(O-dmf) 2 } 2 (HL·dmf) 2 ]·nS (dmf = dimethylformamide) [1Ln, Ln = Sm (nS = 2dmf), Eu (nS = 1.5dmf·2MeCN)], also the best-defined of all the arrays studied. The heaviest lanthanides give trinuclear Ln(OH) 3 · 2Ln(LH)·xdmf·yH 2 O (2Ln, Ln = Yb, Lu), while both oxo and hydroxo species are isolable with Eu: trinuclear Eu 3 O(L)-(LH)(LH 4 )·13dmf (3) and tetranuclear Eu 4 O(OH) 2 (L)(LH 2 ) 2 -(LH 4 )·12dmf (9), both somewhat atypical species containing uncoordinated thiacalixarene molecules within the lattice. Anion (NO 3 , ClO 4 ) coordination, as in the tri-and tetranuclear species, 4-6Ln, 9, 10Ln, 11Ln, 12, seems especially fav-

Biosensing with ferromagnet-based magnetoresistive devices has been dominated by electrical detection of particle-induced changes to the devices' static magnetic configuration.There are however potential advantages to be gained from using field dependent, high frequency magnetization dynamics for magnetic particle detection. Here we demonstrate the use of nano-confined ferromagnetic resonances in periodically patterned magnetic films for the detection of adsorbed magnetic particles with diameters ranging from 6 nm to 4 µm. are observed for a large range of coverages, even when hole-localized particles are covered by quasi-continuous particle sheets. For large particles however, preferential adsorption no longer occurs, leading to resonance shifts with polarities which are independent of the mode localization. Analogous shifts are seen in continuous layers where, for small particles, the shift of the layer's fundamental mode is typically about 10 times less than in patterned systems and induced by relatively weak fields emanating beyond the particle in the direction of the static applied field. This highlights the importance of having confined modes consistently positioned with respect to nearby particles.

Single crystal X-ray diffraction data measured at 100 K for Dianin's compound (DC) and eighteen of its clathrates formed with a wide range of guest molecules provide considerable insight into the way the host adjusts to accommodate guest molecules. Detailed information is also obtained regarding the location, orientation and dynamics of the guests in the host cavity. Although all unit cells are closely similar in size, the host undergoes significant change in response to the imprisonment of its various guests. Enclathration typically results in a larger cell and cavity volume, but for the small molecules methanol, ethanol and nitromethane the host actually shrinks significantly around the guests in the cavity. In most clathrates there is evidence of close contacts between atoms in the guest and the phenol-OH group and/or ring of the DC host. The series of clathrates formed by benzene, toluene and the halobenzenes shows the orientation of the benzene ring to be progressively modifed by the increasing size of the substituent atom or group on the ring in a systematic manner that reflects functional group contributions to van der Waals volumes. € R3 and a hexagonal cell with a ~ 27 Å, c ~ 11 Å, 12,13 which requires most guest molecules to be disordered about the threefold axis and the inversion centre at the waist of the cavity. ASS OCIA TED C ONTENT Supporting Information. Experimental procedures and details of crystallography. This material is available free of charge via the Internet at http://pubs.acs.org.

The title compound undergoes two order-disorder transitions between 15 and 299 K, dictated by ordering of the guest molecules in the host cages, and resulting in three related crystal structures. We anticipate behaviour of this kind to be widespread, and speculate that the concept of "the crystal structure" for individual Dianin's clathrates may be elusive.

FePt nanoparticles have been assembled on the surface of MCM-41 silicates. The incorporation resulted in highly dispersed particles. Under thermal treatment for 1 h at temperatures up to 560 °C, no signs of agglomeration occurred. The silicates have also been used as a template to assist in the solution synthesis of FePt particles. The resultant particles were distributed over the surface and possibly inside the silcate pores with a range of sizes (3−10 nm).

An ab initio potential-energy surface for the ground doublet state of BH 3 ϩ has been constructed at the QCISD͑T͒/6-311G(d, p) level of theory. Classical simulations of the collision between BH ϩ and H 2 ͑D 2 ) and isotopic analogs show that the deep BH 3 ϩ well gives rise to substantial ''scrambling'' of the hydrogen and deuterium atoms leading to BHD ϩ ϩD, BD ϩ ϩHD, and BD 2 ϩ ϩH products.