Ligand Effects on the Spin Relaxation Dynamics and Coherent Manipulation of Organometallic La(II) Potential Quits.

We present pulsed electron paramagnetic resonance (EPR) studies on three La(II) complexes, [K(2.2.2-cryptand)][La(Cp')] (), [K(2.

Metal-carbon bonding in early lanthanide substituted cyclopentadienyl complexes probed by pulsed EPR spectroscopy.

We examine lanthanide (Ln)-ligand bonding in a family of early Ln complexes [Ln(Cp)] (1-Ln, Ln = La, Ce, Nd, Sm; Cp = CHBu-1,3) by pulsed electron paramagnetic resonance (EPR) methods, and provide the first characterization of 1-La and 1-Nd by single crystal XRD, multinuclear NMR, IR and UV/Vis/NIR spectroscopy. We measure electron spin and relaxation times of 12 and 0.2 μs (1-Nd), 89 and 1 μs (1-Ce) and 150 and 1.

Evaluation of the Accessibility of Molecules in Hydrogels Using a Scale of Spin Probes.

In this work, we explored by means of electron paramagnetic resonance (EPR) spectroscopy the accessibility of a series of spin probes, covering a scale of molecular weights in the range of 200-60,000 Da, in a variety of hydrogels: covalent network, ionotropic, interpenetrating polymer network (IPN) and semi-IPN. The covalent gel network consists of polyethylene or polypropylene chains linked isocyanate groups with cyclodextrin, and the ionotropic gel is generated by alginate in the presence of Ca ions, whereas semi-IPN and IPN gel networks are generated in a solution of alginate and chitosan by adding crosslinking agents, Ca for alginate and glutaraldehyde for chitosan. It was observed that the size of the diffusing species determines the ability of the gel to uptake them.

Engineering electronic structure to prolong relaxation times in molecular qubits by minimising orbital angular momentum.

The proposal that paramagnetic transition metal complexes could be used as qubits for quantum information processing (QIP) requires that the molecules retain the spin information for a sufficient length of time to allow computation and error correction. Therefore, understanding how the electron spin-lattice relaxation time (T) and phase memory time (T) relate to structure is important. Previous studies have focused on the ligand shell surrounding the paramagnetic centre, seeking to increase rigidity or remove elements with nuclear spins or both.

Chromium chains as polydentate fluoride ligands for actinides and group IV metals.

The reactions of {Cr6} horseshoe chains {[nPr2NH2]3[Cr6F11(O2CtBu)10]}2, 1 and precursors of actinides and group IV metals led to a series of ring complexes [nPr2NH2][Cr7TiF6O2(O2CtBu)16], 2, [nPr2NH2][Cr6Ti2F5O3(O2CtBu)16], 3, [Cr6ThF7(O2CtBu)15 (Me2SO)], 4, [(nPr2NH2)2(Cr6Th2F12(O2CtBu)16)], 5 and [nPr2NH2][Cr6U2O2F8(O2CtBu)16(Me2SO)], 6. X-ray structure studies indicate that the {Cr6} chains maintain their structures in these complexes, acting as polydentate fluoride ligands. Their static magnetic properties were measured and fitted by isotropic exchange Hamiltonian.

A sub-Kelvin cryogen-free EPR system.

We present an EPR instrument built for operation at Q band below 1K. Our cryogen-free Dewar integrates with a commercial electro-magnet and bridge. A description of the cryogenic and RF systems is given, along with the adaptations to the standard EPR experiment for operation at sub-Kelvin temperatures.

Actinide covalency measured by pulsed electron paramagnetic resonance spectroscopy.

Our knowledge of actinide chemical bonds lags far behind our understanding of the bonding regimes of any other series of elements. This is a major issue given the technological as well as fundamental importance of f-block elements. Some key chemical differences between actinides and lanthanides-and between different actinides-can be ascribed to minor differences in covalency, that is, the degree to which electrons are shared between the f-block element and coordinated ligands.

Novel mononuclear and 1D-polymeric derivatives of lanthanides and (η-benzoic acid)tricarbonylchromium: synthesis, structure and magnetism.

Two series of novel heteroleptic derivatives of lanthanides and (η-benzoic acid)tricarbonylchromium (benchrotrenecarboxylic acid) were synthesized and characterized: mononuclear complexes [Ln(BcrCOO)(acac)(HO)] (Ln = Eu (1), Gd (2), Tb (3a), Dy (4a), Ho (5a)) and 1D-polymeric ones [Ln(BcrCOO)(acac)(HO)] (Ln = Tb (3b), Dy (4b), Ho (5b), Er (6), Tm (7), Yb (8) and Y (9)), Bcr = (η-CH)Cr(CO). The molecular and crystal structures of the obtained compounds were determined. Complexes 3a, 4a, 4b, 6 and 8 were found to exhibit SMM properties.

Toward Molecular 4f Single-Ion Magnet Qubits.

Quantum coherence is detected in the 4f single-ion magnet (SIM) Yb(trensal), by isotope selective pulsed EPR spectroscopy on an oriented single crystal. At X-band, the spin-lattice relaxation (T1) and phase memory (Tm) times are found to be independent of the nuclei bearing, or not, a nuclear spin. The observation of Rabi oscillations of the spin echo demonstrates the possibility to coherently manipulate the system for more than 70 rotations.

A monometallic lanthanide bis(methanediide) single molecule magnet with a large energy barrier and complex spin relaxation behaviour.

We report a dysprosium(iii) bis(methanediide) single molecule magnet (SMM) where stabilisation of the highly magnetic states and suppression of mixing of opposite magnetic projections is imposed by a linear arrangement of negatively-charged donor atoms supported by weak neutral donors. Treatment of [Ln(BIPM)(BIPMH)] [Ln = Dy, ; Y, ; BIPM = {C(PPhNSiMe)}; BIPMH = {HC(PPhNSiMe)}] with benzyl potassium/18-crown-6 ether (18C6) in THF afforded [Ln(BIPM)][K(18C6)(THF)] [Ln = Dy, ; Y, ]. AC magnetic measurements of in zero DC field show temperature- and frequency-dependent SMM behaviour.

Ion exchange in alginate gels--dynamic behaviour revealed by electron paramagnetic resonance.

The formation of alginate gel from low molecular weight alginate and very low molecular weight alginate in the presence of divalent cations was investigated using Electron Paramagnetic Resonance (EPR) spectroscopy. The transition from sol to gel in the presence of divalent cations was monitored by the changes in the dynamics of spin labelled alginate. The immobilisation of the spin labelled alginate in the gel reflects the strength of interaction between the cation and alginate chain.

Cationic spin probe reporting on thermal denaturation and complexation-decomplexation of BSA with SDS. Potential applications in protein purification processes.

In this work, we present evidence on the suitability of spin probes to report on the thermal treatment of bovine serum albumin (BSA), in the temperature range 293-343 K, and indirectly monitor the release of sodium dodecyl sulfate (SDS) from its complex with BSA using a covalent gel with β-cyclodextrin (β-CD) in the network. The spin probes used, 5- and 7-doxyl-stearic acids (5-DSA, 7-DSA) or 4-(N,N'-dimethyl-N-hexadecyl)ammonium-2,2',6,6'-tetramethylpiperidine-1-oxyl iodide (CAT16), present similar, fatty acid-like structural features. Their continuous wave electron paramagnetic resonance (CW-EPR) spectra, however, reflect different dynamics when complexed with BSA: a restricted motion for 5-DSA, almost nonsensitive to the heating/cooling cycle, and a faster temperature-dependent dynamic motion for CAT16.

Properties of polyethylene glycol/cyclodextrin hydrogels revealed by spin probes and spin labelling methods.

The properties of a gel consisting of a covalent network formed by the reaction of isocyanate end-capped polyethylene glycol (PEG) with β-cyclodextrin, were investigated by EPR spectroscopy. Spin-labelled cyclodextrin was incorporated into the cross-link points of the gel and at the chain ends. The dynamics of the gel fibres as reported by the spin label, was found to be sensitive to the H-bonding ability of the solvent, density of cross-links and temperature.