Synergistic photomagnetic effects in coordination polymer heterostructure particles of Hofmann-like Fe(4-phenylpyridine)2[Ni(CN)4]·0.5H2O and K0.4Ni[Cr(CN)6]0.8·nH2O.

New nanometer scale heterostructure particles of the two-dimensional Hofmann-like Fe(ii) spin-crossover network, Fe(phpy)2[Ni(CN)4]·0.5H2O {phpy = 4-phenylpyridine}, and the Prussian blue analogue K0.4Ni1.0[Cr(CN)6]0.8·nH2O (NiCr-PBA) have been developed, exhibiting synergistic photomagnetic effects, whereby the LIESST (light-induced electron spin-state trapping) effect in the Hofmann-like material induces a magnetization change in the NiCr-PBA. A variety of microscopic and spectroscopic techniques demonstrate the heterogeneous growth of the NiCr-PBA on the Hofmann seed particles and show the Hofmann compound retains its thermal and photoinduced spin transition properties in the heterostructure. The photoinduced magnetization change in the NiCr-PBA network arises from coupling of the two lattices despite dissimilar structure types. Isothermal magnetization minor hysteresis loop studies at 5 K show light absorption leads to changes in the local anisotropy of NiCr-PBA magnetic domains, providing direct evidence for a general magnetomechanical mechanism of light-switchable magnetism in coordination polymer heterostructures combining a photoactive material with a magnet.

Introducing Dimensionality to the Archetypical Mn12 Single-Molecule Magnet: a Family of [Mn12]n Chains.

The [Mn12O12(O2CR)16(L4)] family (R = various; L = terminal ligand) of clusters holds a special place in molecular magnetism; they are the most well-studied single-molecule magnets (SMMs). Targeted linkage of these SMMs has now been achieved for the first time. The resulting chain structures have been confirmed crystallographically, and the magnetic properties, up to 1.14 GPa, and high-field electron paramagnetic resonance spectra have been collected and analyzed.

Light-induced magnetization changes in a coordination polymer heterostructure of a Prussian blue analogue and a Hofmann-like Fe(II) spin crossover compound.

Coordination polymer thin film heterostructures of the Prussian blue analogue Ni(II)b[Cr(III)(CN)6](0.7)·nH2O (NiCr-PBA) and the 3D Hofmann-like spin crossover compound Fe(azpy)[Pt(CN)4]·xH2O {azpy = 4,4'-azopyridine} have been developed, and spin transition properties have been characterized via SQUID magnetometry and Raman spectroscopy. The magnetic response of the ferromagnetic NiCr-PBA layer (T(c) ≈ 70 K) can be altered by inducing the LIESST effect (light-induced excited spin state trapping) in the coupled paramagnetic Fe(II) spin crossover material. Whereas an increase in magnetization is measured for the single-phase Fe(azpy)[Pt(CN)4]·xH2O, a decrease in magnetization is observed for the heterostructure. These results indicate the LIESST effect alone cannot account for the sign and magnitude of the magnetization change in the heterostructure, but the temperature profile of the magnetization shows that significant changes in the NiCr-PBA network are correlated to the spin state of the Hofmann-like SCO network.

Absolute magnetic susceptibility of rat brain tissue.

PURPOSE: This study was performed to test the commonly held hypothesis that the absolute magnetic susceptibility of brain tissue is close to that of water since water accounts for over 50% of the tissue composition. In addition, the absolute value of susceptibility of brain tissue is needed for the development of materials that are implanted into or in close proximity to tissue. METHODS: The absolute magnetic susceptibilities of different sections of rat brain, which were exsanguinated and perfusion-fixed, have been measured in a commercial superconducting quantum interference device magnetometer operating in fields up to 7T. RESULTS: The average measured values ranged from -(9.51 ± 0.01) × 10(-6) for the cerebellum to -(8.99 ± 0.01) × 10(-6) for a mixture of hippocampus, corpus callosum, and striatum. The time evolution of the samples was also studied, and deviations of <1% were observed after 4 weeks, although this trend was sample-specific. CONCLUSION: The measured susceptibilities are close to the value measured for high-performance liquid chromatography H2 O and depend on the amount of gray and white matter regions present in the samples.

Preorganized assembly of three iron(II) or manganese(II) ß-diketiminate complexes using a cyclophane ligand.

A trinucleating cyclophane bearing three ß-diketimine arms, and the corresponding iron(II) and manganese(II) complexes have been synthesized and characterized. The three metal ions are oriented towards the internal void space, and are coordinated by a N2Br2 donor set, in which a unique combination of µ(3), µ, and terminal coordination modes are observed for the halide donors.

MR measurement of alloy magnetic susceptibility: towards developing tissue-susceptibility matched metals.

Magnetic resonance imaging (MRI) can be used to relate structure to function mapped with high-temporal resolution electrophysiological recordings using metal electrodes. Additionally, MRI may be used to guide the placement of electrodes or conductive cannula in the brain. However, the magnetic susceptibility mismatch between implanted metals and surrounding brain tissue can severely distort MR images and spectra, particularly in high magnetic fields. In this study, we present a modified MR method of characterizing the magnetic susceptibility of materials that can be used to develop biocompatible, metal alloys that match the susceptibility of host tissue in order to eliminate MR distortions proximal to the implant. This method was applied at 4.7T and 11.1T to measure the susceptibility of a model solid-solution alloy of Cu and Sn, which is inexpensive but not biocompatible. MR-derived relative susceptibility values of four different compositions of Cu-Sn alloy deviated by less than 3.1% from SQUID magnetometry absolute susceptibility measurements performed up to 7T. These results demonstrate that the magnetic susceptibility varies linearly with atomic percentage in these solid-solution alloys, but are not simply the weighted average of Cu and Sn magnetic susceptibilities. Therefore susceptibility measurements are necessary when developing susceptibility-matched, solid-solution alloys for the elimination of susceptibility artifacts in MR. This MR method does not require any specialized equipment and is free of geometrical constraints, such as sample shape requirements associated with SQUID magnetometry, so the method can be used at all stages of fabrication to guide the development of a susceptibility matched, biocompatible device.