Rare-Earth (RE = Y, Gd, Tb, Dy, Ho, and Er) Chains Bridged with a Triplet Biradical and Magnetic Hysteresis Recorded for RE = Tb.

Complex formation of 5-tert-butyl-1,3-phenylene bis(tert-butyl nitroxide) and rare-earth (RE) metal ions gave a linear chain where each nitroxide O atom is directly bonded to the RE ion. The bridge was proven to be a ground triplet molecule in the complexes. A hysteresis loop was recorded below 2.8 K as a single-chain magnet for the RE = Tb derivative.

Bilayered lanthanide squarate hydrates (Ln = Eu to Lu) and magnetization reversal barriers of 21 K for Ln = Tm and 57 K for Yb.

A squarate (sq) bridge was applied to heavy lanthanide (Ln) complexes for possible development of high-performance single-ion magnets (SIMs). A selective synthetic method for lanthanide squarate hydrates [Ln2(sq)3(H2O)8]n (abbreviated as Ln-sq) has been established, where Ln stands for Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. As the crystallographic analysis clarified, they all form a bilayer polymeric structure, which is isomorphic to known Eu-sq and Tb-sq. The coordination structures are described as an almost ideal square antiprism with D4d symmetry. Frequency-dependent susceptibility was recorded in alternating-current magnetic measurements for Ln = Tb, Dy, Er, Tm, and Yb. In particular, as for less studied Ln-based SIMs, the effective magnetization-reversal barriers, Ueff/kB = 21.4 ± 0.4 K (in a bias field of 1800 Oe) and 57.0 ± 0.4 K (400 Oe), were characterized for Tm-sq and Yb-sq, respectively, according to the Orbach-type relaxation mechanism plus a direct or the Raman mechanism. The barrier found for Yb-sq is the highest among those for all the compounds investigated here, and also regarded as one of the largest values for the Yb-based SIMs known so far. The complete-active-space self-consistent-field (CASSCF) calculation was applied to Tm- and Yb-sq. The ground doublet states with mJ = ±6 for the Tm3+ ion and mJ = ±7/2 for the Yb3+ ion were reproduced.

Continuous Condensed Triplet Accumulation for Irradiance-Induced Anticounterfeit Afterglow.

Afterglow room-temperature emission that is independent of autofluorescence after ceasing excitation is a promising technology for state-of-the-art bioimaging and security devices. However, the low brightness of the afterglow emission is a current limitation for using such materials in a variety of applications. Herein, the continuous formation of condensed triplet excitons for brighter afterglow room-temperature phosphorescence is reported. (S)-(-)-2,2'-Bis(diphenylphosphino)-1,1'-binaphthyl ((S)-BINAP) incorporated in a crystalline host lattice showed bright green afterglow room-temperature phosphorescence under strong excitation. The small triplet-triplet absorption cross-section of (S)-BINAP in the whole range of visible wavelengths greatly suppressed the deactivation caused by Förster resonance energy transfer from excited states of (S)-BINAP to the accumulated triplet excitons of (S)-BINAP under strong continuous excitation. The steady-state concentration of the triplet excitons for (S)-BINAP reached 2.3 × 10-2  M, producing a bright afterglow. Owing to the brighter afterglow, afterglow detection using individual particles with sizes approaching the diffraction limit in aqueous conditions and irradiance-dependent anticounterfeiting can be achieved.

Lanthanide induced variability in localised CoII geometries of four triangular L3Co3 IILnIII complexes.

Four tetranuclear heterobimetallic triangle complexes [L3Co3Dy(NO3)2(H2O)(MeOH)5](NO3) (C1), [L3Co3Gd(NO3)3(MeOH)4] (C2), [L3Co3La(NO3)2(H2O)6](NO3)(H2O) (C3), and [L3Co3TbCl(NO3)2(H2O)0.5(MeOH)3.5] (C4), where H2L = 1,4-bisformylnaphthalene-2,3-diol, have been synthesised and structurally characterised. Each complex crystallises with a complete molecule in the asymmetric unit (Z' = 1) and displays near perfect octahedrality in two out of three CoII centres. The third CoII ion assumes a different coordination geometry in each complex: six-coordinate octahedral in C1, six-coordinate with a distortion towards trigonal prismatic in C2, five-coordinate trigonal bipyramidal in C3, and five-coordinate square pyramidal in C4; which has been attributed to increasing lanthanide cation size, coupled with a non-macrocyclic coordination environment. Continuous Shape Measurement (CShM) calculations and octahedral distortion parameter calculations were performed, using the SHAPE and OctaDist software packages, respectively, in order to aid in the assessment of each metal centre's local coordination geometry. The preliminary magnetic investigation of C3 found χ m T = 9.4 cm3 K mol-1 at 300 K and M = 7.1 µ B at 1.8 K, which are approximately two thirds the maximum theoretical values for three CoII ions and indicates the presence of a relatively large zero-field splitting parameter (D/k B = 65 K) operative in each CoII ion rather than exchange coupling between the CoII centres.

Self-assembly of non-macrocyclic triangular Ni3Ln clusters.

The synthesis and structural characterisation of four new heterometallic tetranuclear complexes is reported. Three L3Ni3Ln type complexes, where Ln = La (C1), Eu (C2), and Gd (C3), have been fully characterised including DC and AC magnetic measurements. A fourth complex featuring a diamagnetic BaII ion at its centre is also reported with structural characterisation. Structural elucidation showed that all four complexes successfully self-assembled from a stoichiometric mixture of the acyclic ligand, 1,4-diformylnaphthalene-2,3-diol, with nickel(II) nitrate and the appropriate heavy metal salt to produce the same near planar Ni3MO12 core. Ferromagnetic interactions were found to dominate the ground state of C3, exhibiting a maximal spin ground state of 13/2. The exchange coupling is quantitatively discussed along with the nickel(II) zero-field splitting effect. AC magnetic susceptibility experiments were carried out, but no frequency dependent signals were observed and thus no observable slow relaxation of magnetisation.

Metallocyclic CuII-LnIII Single-Molecule Magnets from the Self-Assembly of 1,4-Diformylnaphthalene-2,3-diol.

We report the synthesis and characterization of seven new tetranuclear 3d-4f complexes derived from the 3:3:1 reaction of 1,4-diformylnaphthalene-2,3-diol (H2 L) with copper(II) nitrate and a lanthanide salt, Ln = Tb [L 3Cu3TbCl2(NO3)2(H2O)2] (C1), Ho [L 3Cu3HoCl3(H2O)3(MeOH)](H2O) (C2), Er [L 3Cu3ErCl3(H2O)3.5(MeOH)0.5](H2O) (C3), Gd [L 3Cu3Gd(NO3)2(H2O)2(MeOH)](NO3) (C4), Dy [L 3Cu3Dy(NO3)2(H2O)2(MeOH)](NO3) (C5), Yb [L 3Cu3Yb(NO3)2(H2O)2(MeOH)](NO3) (C6), and La [L 3Cu3La(NO3)2(H2O)2(MeOH)](NO3) (C7). Structural elucidation showed that the self-assembly using the acyclic ligand system was successful for all seven complexes, which exhibit the same near-planar Cu3LnO12 core. Five complexes (C1, C2, and C4-C6) were magnetically characterized at 300 K and 1.8 K. Complexes C1, C4, and C5 were observed to have ferromagnetic ground states and showed appreciable frequency dependence in their AC magnetic measurements, which yielded effective barriers between 7.82(4) and 13.2(3) K, confirming the presence of single-molecule magnet properties.

A Computed Tomographic Assessment of Tracheostomy Tube Placement in Patients with Chronic Neurological Disorders: The Prevention of Tracheoarterial Fistula.

Objective Tracheoarterial fistula (TAF) is a rare but devastating complication of tracheostomy caused by pressure necrosis from the elbow, tip, or over-inflated cuff of the tracheostomy tube. The incidence of TAF is reportedly higher in patients with neurological disorders than in those without such disorders. To evaluate the incidence of and factors contributing to the misalignment of tracheostomy tubes in bedridden patients with chronic neurological disorders. Methods We retrospectively assessed three-dimensionally reconstructed serial computed tomography (CT) images to see if the tip of the tube made contact with the tracheal wall and if the main arteries were running adjacent to the tube's elbow, tip or cuff. Results The tip of the tube was in contact with the tracheal wall in 14 of the 30 patients assessed. Among them, the tip was adjacent to the innominate artery in eight, the aortic arch in three and an aberrant right subclavian artery in one. In one patient with the tube tip adjacent to the aortic arch and the other four patients, the cuff of the tube was adjacent to the innominate artery across the tracheal wall. Patients with the tube tip in contact with the anterior tracheal wall had a significantly greater cervical lordosis angle than those without contact (p<0.05). Conclusion More than half of tracheostomized patients with chronic neurological disorders had a latent risk of TAF. The variability in the location of the innominate artery, anomalies of the aortic arch, and skeletal deformities may therefore be contributing factors.

A prominent elevation of glial fibrillary acidic protein in the cerebrospinal fluid during relapse in neuromyelitis optica.

Neuromyelitis optica (NMO) is a neurologic disease characterized by severe optic neuritis, longitudinally extended, transverse myelitis and serum aquaporin-4 (AQP4) antibody. Our recent neuropathological study revealed the extensive loss of AQP4 and glial fibrillary acidic protein (GFAP), an astrocyte-specific protein, in NMO lesions, but not in MS lesions, suggesting that severe astrocytic damage or dysfunction may be related to the pathogenesis of NMO. Here we report a patient of NMO, in which the cerebrospinal fluid (CSF) levels of GFAP were measured both during relapse of myelitis and after high-dose intravenous methylprednisolone (HIMP). The patient was a 34-year old woman with two previous episodes of optic neuritis. She developed myelitis longitudinally extending from C3 to T12 with contrast enhancement, and was AQP4 antibody-positive. In the acute phase, the GFAP level in the cerebrospinal fluid (CSF) was prominently elevated (18,966.7 ng/ml) as compared with controls (0.6 +/- 0.33 ng/ml). However, following HIMP, the clinical and MRI findings improved, and the CSF-GFAP level was near-normal (2.1 ng/ml). The CSF of myelin basic protein was also elevated in relapse (1,016.0 pg/ml), and became lower but still remained high (158.7 pg/ml) after HIMP compared with controls (3.36 +/- 3.83 pg/ml). The prominent elevation of the CSF-GFAP level in relapse of NMO, followed by its sharp decline after therapy, suggests severe astrocytic damage with a temporal profile distinct from that of the demyelinating process in NMO. CSF-GFAP may be useful as a biomarker of NMO.

Increase of complement fragment C5a in cerebrospinal fluid during exacerbation of neuromyelitis optica.

Complement is thought to play a pivotal role in neuromyelitis optica (NMO) pathogenesis. Anaphylatoxins (C3a, C4a, and C5a), produced in complement activation, have proinflammatory potential, and thereby may play an important role. We measured concentrations of anaphylatoxins in CSF and sera, obtained from patients with NMO (n=15), multiple sclerosis (MS) (n=15), and other neurological disease (OND) (n=12), and evaluated their clinical implications. The CSF-C5a levels were elevated significantly in NMO patients, especially in patients with multiple enhanced lesions on MRI. The CSF-C5a levels correlated with the severity of exacerbation. Our results may provide a rationale for anti-complement therapies of NMO.

[New insights into the pathogenesis of neuromyelitis optica].

Recently, the disease-specific antibody was found in the sera from neuromyelitis optica (NMO) patients, and its target was identified as aquaporin-4 (AQP4), mainly expressed in astroglial foot processes. In our immunohistochemical studies, loss of AQP4 and glial fibrillary acidic protein (GFAP) was evident in about 90% of NMO lesions, especially in perivascular areas of acute inflammatory lesions where immunoglobulins and complements were deposited. In contrast, myelin basic protein (MBP)-stained myelinated fibers were relatively preserved in those lesions, which probably suggested the secondary damage of myelin sheaths following astrocytic damage. Recently, there are developing evidences of the effect of AQP4 antibody in vitro or in vivo. In HEK293 cells transfected with AQP4, AQP4 antibody could bind to the membrane AQP4, and induced the degradation and endocytosis of AQP4 in complement-dependent manner. In vitro experiments by primary cultured astrocytes, AQP4 antibody had cytotoxic effects with complement, and also could impair the astrocytic function such as the maintenance of the blood brain barrier or glutamate homeostasis. In vivo study, the lesions lacking AQP4 and GFAP was appeared by passive-transferred Lewis rats with human purified IgG from NMO patients. Furthermore, in cerebrospinal fluid (CSF) biomarker study, astrocytic damage reflected by marked increase of CSF-GFAP, far severe than demyelination (CSF-MBP), was evident in NMO but not in classical multiple sclerosis (MS). These evidences suggested the pathogenic role of AQP4 antibody with astrocytopathy in NMO. Now it is indispensable to check the AQP4 antibody,and is important to reconsider the role of astrocyte in demyelinating disorders.