Xin-Yi Wang

Constructing magnetic molecular solids by employing three-atom ligands as bridges

The combination of some three-atom bridges with paramagnetic 3d transition metal ions results in the systematic isolation of molecular magnetic materials, ranging from single-molecule and single-chain magnets to layered weak ferromagnets and three-dimensional porous magnets. The design strategy and role of secondary components, such as co-ligands, templates and other mixed short ligands are discussed.

A single-molecule magnet based on heptacyanomolybdate with the highest energy barrier for a cyanide compound.

Three trinuclear Mn2Mo molecules based on the orbitally degenerate [Mo(CN)7](4-) anion were prepared, one of which is the first single-molecule magnet (SMM) based on heptacyanomolybdate. The blocking temperature and the energy barrier (U = 40.5 cm(-1)) are records for a cyanide-based SMM. Wide hysteresis loops and sharp quantum tunneling steps were observed from single-crystal measurements.

Cation-Dependent Magnetic Ordering and Room-Temperature Bistability in Azido-Bridged Perovskite-Type Compounds

A series of end-to-end azido-bridged perovskite-type compounds [(CH3)nNH4-n][Mn(N3)3] (n = 1-4) were synthesized and characterized. Structural phase transitions indicating the general lattice flexibility were observed and confirmed by the crystal structures of different phases. These materials show cation-dependent magnetic ordering at up to 92 K and magnetic bistability near room temperature.

Field-Induced Slow Magnetic Relaxation in Cobalt(II) Compounds with Pentagonal Bipyramid Geometry

Field-induced slow magnetic relaxation was observed for air-stable mononuclear cobalt(II) compounds with pentagonal bipyramid geometry. These are the first examples of such behavior observed in the seven-coordinated mononuclear 3d metal compounds.

Detailed Magnetic Studies on Co(N3)2(4-acetylpyridine)2 :a Weak-Ferromagnet with a Very Big Canting Angle

The magnetic properties of Co(N 3) 2(4acpy) 2 have been thoroughly reexamined on both powder and well-oriented single crystal samples. This azido-bridged cobalt compound of (4, 4) layer shows a weak-ferromagnetic state below T C = 11.2 K. The magnetic axes were determined to be along the crystallographic a*, b, and c axes for the monoclinic space group P2 1/c. The easy axis lies along the b-axis, the canting is along the a*-axis, and the hard axis is along the c-axis. Strong anisotropy due to the oriented moments in the ordered state and/or the single-ion anisotropy of Co (2+) exists in the whole temperature range from 2 to 300 K. Below T C, very big spontaneous magnetization was observed and was attributed to the very big canting angle (15 degrees at 2 K). A possible spin configuration was then proposed to explain the experimental results. The origin of the big spin canting was discussed, and a weak-ferromagnetic approach toward molecular magnets with big spontaneous magnetization was proposed accordingly.

A Docosanuclear {Mo8Mn14} Cluster Based on [Mo(CN)7]4−†

One of the recent strategies being explored for obtaining molecular magnets with enhanced properties is the incorporation of heavier transition metals from the 4d and 5d metal ions. A central player in this area of research is the cyanide ligand, which can be used to prepare mixed metal clusters with unusual properties. Of particular interest is the fact that cyanide molecules containing 4d or 5d ions or combinations of them with 3d ions have been predicted to behave as singlemolecule magnets (SMMs) with higher blocking temperatures TB than those based on 3d ions. They are also expected to exhibit properties such as anisotropic magnetic exchange interactions. A main driving force for the high activity in cyanide magnetism is that the use of cyanometalates in reactions with metal ions equipped with capping ligands present several advantages, such as control over the sign of magnetic interactions in most cases and also predictable structures based on the building block approach. Magnetic anisotropy can be conveniently introduced by choosing the appropriate preformed 4d or 5d cyanometalate anion. The observation of SMM behavior with 4d and 5d metal ions with oxygen-type bridging ligands is limited to only one case, but there are a number of SMMs from the heavier congeners of Groups 6 and 7 with the precursors [(Me3tacn)Mo (CN)3], [7] [Mo(CN)8] 3 , 9] [W(CN)8] 3 , [Re(CN)7] 3 , and [(triphos)Re(CN)3] . In contrast to the widely investigated anion [Mo(CN)8] 3 , 8, 9] the heptacyanomolybdate derivative [Mo(CN)7] 4 has received much less attention in the molecular magnetism field, presumably because of the synthetic challenges in the preparation and handling of this anion. Unlike the hexaand octacyanometalates, the [Mo(CN)7] 4 anion favors low-symmetry extended structures with pronounced magnetic anisotropy. 13] The results of theoretical investigations have suggested that [Mo(CN)7] 4

Synthesis, Structure, and Magnetism of Three Azido-Bridged Co2+ Compounds with a Flexible Coligand 1,2-(Tetrazole-1-yl)ethane

By utilizing suitable coligand endi (1,2-(tetrazole-1-yl)ethane)) with variable conformations, we synthesized three new azido-bridged Co(2+) compounds with molecular formulas Co(endi)(N3)2 (1, 3) and Co(endi)2(N3)2 (2) by tuning the stoichiometric ratio of ligand/metal and the concentration of the solution. All of the compounds have been characterized structurally and magnetically. In all three structures, the azide ions use the end-to-end mode to link the Co(2+) centers to the 1D chain (1) and 2D (4,4) layers (2 and 3). The endi coligands adopt a trans conformation in compound 1 and a gauche conformation in compounds 2 and 3. Linked by bridging endi, the 1D chains in compound 1 and 2D layers in compound 3 are extended, resulting in the final 2D layer for compound 1 and the 3D network for compound 3, whereas in compound 2, the endi acts as only a terminal ligand to separate the 2D layers. Compound 1 consists of dual end-to-end azido-bridged 1D Co(2+) chains that are linked by trans endi into a 2D layer and are further extended to a 3D framework through H bonds. Compound 2 is a 2D (4,4) layer that is connected by end-to-end azido ions. The gauche endi ligands act as terminal ligands to separate the neighboring layers thoroughly. Compound 3 has a (4,4) 2D layer that is similar to that of compound 2, and these layers are further extended to a 3D network through gauche endi. The magnetic investigation shows that compound 3 is antiferromagnetically coupled and compound 2 is a weak ferromagnet with a critical temperature of 22 K, which is quite high compared with that of the previously reported 2D azido-bridged Co(2+) compounds.

Effects of the preoperative administration of Yunnan Baiyao capsules on intraoperative blood loss in bimaxillary orthognathic surgery: A prospective, randomized, double-blind, placebo-controlled study

Yunnan Baiyao is a well-known Chinese herbal medicine that has been used as a haemostatic drug for nearly 100 years. The aim of this clinical trial was to evaluate the efficacy and safety of Yunan Baiyao capsules on the reduction of blood loss in bimaxillary orthognathic surgery. 87 consecutive patients scheduled for simultaneous maxillary Le Fort I osteotomies and bilateral sagittal split ramus osteotomies (BSSRO) were enrolled in a prospective, randomized, double-blind, placebo-controlled clinical trial. Patients were administered Yunnan Baiyao capsules or placebo capsules, orally for 3 days before surgery. Intraoperative blood loss was estimated and the safety of Yunnan Baiyao capsules was evaluated. The total blood loss in the Yunnan Baiyao group (mean, 330.5+/-134.4 ml) was significantly lower than in the control group (mean, 420.3+/-175.9 ml). No allergic reactions, thromboembolic events or other side effects were recorded in this trial. It can be concluded that the preoperative use of Yunnan Baiyao capsules, in combination with hypotension anaesthesia, results in a reduction in intraoperative blood loss in bimaxillary orthognathic surgery. Yunnan Baiyao capsules are an effective and safe haemostatic Chinese medicine.

End-on azido-bridged 3d-4f complexes showing single-molecule-magnet property.

Four tetranuclear 3d-4f complexes with the 4f centers bridged solely by end-on azide bridges were reported. The [CuTb]2 compound displays single-molecule-magnet behavior with hysteresis loops observed at up to 2.4 K.

Anterior maxillary segmental distraction for correction of maxillary hypoplasia and dental crowding in cleft palate patients: a preliminary report

To evaluate the feasibility of anterior maxillary segmental distraction (AMSD) to correct maxillary hypoplasia and severe dental crowding in cleft lip and palate (CLP) patients, 7 patients (average age 16.4 years) with maxillary hypoplasia, shortened maxillary dental arch length and severe anterior dental crowding secondary to CLP were selected for this study. After anterior maxillary segmental osteotomy, 3 patients were treated using bilateral internal distraction devices, and 4 patients were treated using rigid external distraction devices. Photographs and radiographs were taken to review the improvement in facial profile and occlusion after distraction. An average 10.25 mm anterior maxillary advancement was obtained in all patients after 10-23 days of distraction and 9-16 weeks of consolidation. The sella-nasion-point A (SNA) angle increased from 69.5 degrees to 79.6 degrees. Midface convexity was greatly improved and velopharyngeal competence was preserved. The maxillary dental arch length was greatly increased by 10.1 mm (P<0.01). Dental crowding and malocclusion were corrected by orthodontic treatment. These results show that AMSD can effectively correct the hypoplastic maxilla and severe dental crowding associated with CLP by increasing the midface convexity and dental arch length while preserving velopharyngeal function, and dental crowding can be corrected without requiring tooth extraction.