Christopher A. Muryn

Single pyramid magnets: Dy5 pyramids with slow magnetic relaxation to 40 K.

Single-molecule magnets: A square-pyramidal pentametallic dysprosium cluster was synthesized and showed slow magnetic relaxation at temperatures as high as 40 K. The thermal energy barrier to relaxation of magnetization of this single-molecule magnet was found at a temperature of 530 K and is the largest yet observed for any d- or f-block cluster compound.

Engineering the coupling between molecular spin qubits by coordination chemistry

The ability to assemble weakly interacting subsystems is a prerequisite for implementing quantum information processing and generating controlled entanglement. In recent years, molecular nanomagnets have been proposed as suitable candidates for qubit encoding and manipulation. In particular, antiferromagnetic Cr7Ni rings behave as effective spin-1/2 systems at low temperature and show long decoherence times. Here, we show that these rings can be chemically linked to each other and that the coupling between their spins can be tuned by choosing the linker. We also present calculations that demonstrate how realistic microwave pulse sequences could be used to generate maximally entangled states in such molecules.

Surface relaxation of SrTiO3(001)

Surface X-ray diffraction has been used to examine the 300 K structure of SrTiO3(001)1×1 with a termination of 78% TiO and 22% SrO. The data indicate that a lateral ferroelectric distortion is absent on both terminations, consistent with a recent theoretical calculation. Although the negligible Ti atom relaxation found on the TiO termination is consistent with medium-energy ion scattering data, it differs from recent density functional theory calculations by 0.13 and 0.16 A. In contrast, the Sr displacement towards the SrO surface of 0.22±0.07 A is in good agreement with theory.

Step and point defect effects on TiO2(100) reactivity

Abstract The influence of steps and point defects on the reactivity of TiO 2 (100) to H 2 O has been examined using photoemission spectroscopy. A vicinal surface was prepared by polishing a sample 2.6 ± 0.1° off the (100) plane towards [001]. Point defects in the form of oxygen vacancies were introduced onto the stepped and planar 1 × 1 stoichiometric (100) surfaces by thermal annealing, a 1 × 3 ordered defect array being formed. The interaction of H 2 O with TiO 2 (100) at 130 K and 293 K is found to be independent of O vacancy and step density. H 2 O adsorbs molecularly at 130 K and dissociates to form OH at 293 K.

Spin dynamics of heterometallic Cr7M wheels (M=Mn, Zn, Ni) probed by inelastic neutron scattering

Inelastic neutron scattering has been applied to the study of the spin dynamics of Cr-based antiferromagnetic octanuclear rings where a finite total spin of the ground state is obtained by substituting one Cr(III) ion (s = 3/2) with Zn (s = 0), Mn (s = 5/2) or Ni (s = 1) di-cations. Energy and intensity measurements for several intra-multiplet and inter-multiplet magnetic excitations allow us to determine the spin wavefunctions of the investigated clusters. Effects due to the mixing of different spin multiplets have been considered. Such effects proved to be important to correctly reproduce the energy and intensity of magnetic excitations in the neutron spectra. On the contrary to what is observed for the parent homonuclear Cr8 ring, the symmetry of the first excited spin states is such that anticrossing conditions with the ground state can be realized in the presence of an external magnetic field. Heterometallic Cr7M wheels are therefore good candidates for macroscopic observations of quantum effects.

Lanthanide Template Synthesis of a Molecular Trefoil Knot

We report on a complex featuring three 2,6-pyridinedicarboxamide ligands entwined around a lanthanide (Ln(3+)) ion. The ligand strands can be cyclized by ring-closing olefin metathesis to form a molecular trefoil knot in 58% yield. Demetalation with tetraethylammonium fluoride quantitatively generates the wholly organic 81-atom-loop trefoil knot.

Routes to tin chalcogenide materials as thin films or nanoparticles: a potentially important class of semiconductor for sustainable solar energy conversion

Thin films of tin chalcogenides may find use in photovoltaic devices, and nanocrystals of such materials are attractive due to their tuneable band gaps and potential in photovoltaic, photonic and optoelectronic applications. Tin(II) sulfide (SnS) is of particular interest due to its band gap of 1.4 eV, which is similar to that of silicon (1.1 eV). This review seeks to provide an overview of the chemical routes currently known for the synthesis of tin chalcogenides as thin films or in nanocrystalline form, as well as exploring routes to copper zinc tin sulfide (CZTS) and mesoporous tin chalcogenides.

Probing molecular orientation in corrosion inhibition via a NEXAFS study of benzotriazole and related molecules on Cu(100)

Abstract The orientation of benzotriazole on Cu(100) has been studied using near-edge X-ray absorption fine structure (NEXAFS) at the C and N K-edges. At submonolayer coverage, benzotriazole (C6H5N3) is found to adsorb with the molecular plane close to perpendicular to the Cu(100) surface, as indicated by the polarization dependence of the π∗ features. The orientation of benzimidazole (C7H6N2) and 1-methyl benzotriazole (C7H7N3) on Cu(100) have also been studied, and are found not to be oriented at submonolayer coverage. This, along with the orientation at multilayer coverage suggests a specific first-bonding-layer origin for the corrosion inhibitor properties of benzotriazole.

The orientation of formate and carbonate on ZnO(101̄0)

Abstract Polarisation dependent CK-edge NEXAFS spectra of carbonate and formate species on ZnO(1010) indicate that both species are aligned by the substrate. The carbonate species, formed by adsorption of CO2, is oriented with its molecular plane close to the [0001] azimuth. This suggests a bond geometry in which one O atom of CO2−3 is in the substrate, and a second interacts with a surface cation, consistent with the results of previous cluster calculations. In contrast, the formate species, formed by adsorption of formic acid, is not azimuthally ordered, although the molecular rotation axis is aligned close to the surface normal, consistent with bidentate bonding to a single cation.

C60 adsorption on the quasicrystalline surface of Al70Pd21Mn9

Abstract Room temperature adsorption of C 60 on the flat quasicrystalline surface of Al 70 Pd 21 Mn 9 has been investigated using scanning tunnelling microscopy. A dispersed overlayer is formed at low coverage, with avoidance of step-edges. There is no evidence of island formation or clustering. As the coverage is increased, a higher density layer is formed with no evidence of the formation of hexagonal ordered adsorbate structures seen on other substrates. This is followed by the onset of second layer formation. A range of bonding sites for C 60 molecules is implied from measurements of apparent molecular heights and from thermal effects. Detailed analysis of the surface at a low coverage (∼0.065 ML) provides evidence of adsorbate local order, with Fibonacci ( τ -scaling) relationships between the C 60 molecules. Where this occurs, the preferred adsorption site is tentatively identified as the pentagonal hollow. These local correlations however are not found to extend over larger regions of the surface.