Photoinduced Selective B-H Activation of nido-Carboranes.

The development of new synthetic methods for B-H bond activation has been an important research area in boron cluster chemistry, which may provide opportunities to broaden the application scope of boron clusters. Herein, we present a new reaction strategy for the direct site-selective B-H functionalization of nido-carboranes initiated by photoinduced cage activation via a noncovalent cage···π interaction. As a result, the nido-carborane cage radical is generated through a single electron transfer from the 3D nido-carborane cage to a 2D photocatalyst upon irradiation with green light. The resulting transient nido-carborane cage radical could be directly probed by an advanced time-resolved EPR technique. In air, the subsequent transformations of the active nido-carborane cage radical have led to efficient and selective B-N, B-S, and B-Se couplings in the presence of N-heterocycles, imines, thioethers, thioamides, and selenium ethers. This protocol also facilitates both the late-stage modification of drugs and the synthesis of nido-carborane-based drug candidates for boron neutron capture therapy (BNCT).

Facile Construction of New Hybrid Conjugation via Boron Cage Extension.

Aromatic polycyclic systems have been extensively utilized as structural subunits for the preparation of various functional molecules. Currently, aromatics-based polycyclic systems are predominantly generated from the extension of two-dimensional (2D) aromatic rings. In contrast, polycyclic compounds based on the extension of three-dimensional (3D) aromatics such as boron clusters are less studied. Here, we report three types of boron cluster-cored tricyclic molecular systems, which are constructed from a 2D aromatic ring, a 3D aromatic nido-carborane, and an alkyne. These new tricyclic compounds can be facilely accessed by Pd-catalyzed B-H activation and the subsequent cascade heteroannulation of carborane and pyridine with an alkyne in an isolated yield of up to 85% under mild conditions without any additives. Computational results indicate that the newly generated ring from the fusion of the 3D carborane, the 2D pyridyl ring, and an alkyne is non-aromatic. However, such fusion not only leads to a 1H chemical shift considerably downfield shifted owing to the strong diatropic ring current of the embedded carborane but also devotes to new/improved physicochemical properties including increased thermal stability, the emergence of a new absorption band, and a largely red-shifted emission band and enhanced emission efficiency. Besides, a number of bright, color-tunable solid emitters spanning over all visible light are obtained with absolute luminescence efficiency of up to 61%, in contrast to aggregation-caused emission quenching of, e.g., Rhodamine B containing a 2D-aromatics-fused structure. This work demonstrates that the new hybrid conjugated tricyclic systems might be promising structural scaffolds for the construction of functional molecules.

Direct B-H Functionalization of Icosahedral Carboranes via Hydrogen Atom Transfer.

The efficient and selective functionalization of icosahedral carboranes (C2B10H12) at the boron vertexes is a long-standing challenge owing to the presence of 10 inert B-H bonds in a similar chemical environment. Herein, we report a new reaction paradigm for direct B-H functionalization of icosahedral carboranes via B-H homolysis enabled by a nitrogen-centered radical-mediated hydrogen atom transfer (HAT) strategy. Both the HAT process of the carborane B-H bond and the resulting boron-centered carboranyl radical intermediate have been confirmed experimentally. The reaction occurs at the most electron-rich boron vertex with the lowest B-H bond dissociation energy (BDE). Using this strategy, diverse carborane derivatization, including thiolation, selenation, alkynylation, alkenylation, cyanation, and halogenation, have been achieved in satisfactory yields under a photoinitiated condition in a metal-free and redox-neutral fashion. Moreover, the synthetic utility of the current protocol was also demonstrated by both the scale-up reaction and the construction of carborane-based functional molecules. Therefore, this methodology opens a radical pathway to carborane functionalization, which is distinct from the B-H heterolytic mechanism in the traditional strategies.

Rh-Catalyzed Decarbonylative Cross-Coupling between o-Carboranes and Twisted Amides: A Regioselective, Additive-Free, and Concise Late-Stage Carboranylation.

The convenient cross-coupling of sp2 or sp3 carbons with a specific boron vertex on carborane cage represents significant synthetic values and insurmountable challenges. In this work, we report an Rh-catalyzed reaction between o-carborane and N-acyl-glutarimides to construct various Bcage -C bonds. Under the optimized condition, the removable imine directing group (DG) leads to B(3)- or B(3,6)-C couplings, while the pyridyl DG leads to B(3,5)-Ar coupling. In particular, an unexpected rearrangement of amide reagent is observed in pyridyl directed B(4)-C(sp3 ) formation. This scalable protocol has many advantages, including easy access, the use of cheap and widely available coupling agents, no requirement of an external ligand, base or oxidant, high efficiency, and a broad substrate scope. Leveraging the RhI dimer and twisted amides, this method enables straightforward access to diversely substituted and therapeutically important carborane derivatives at boron site, and provides a highly valuable vista for carborane-based drug screening.

A tetra-nuclear cobalt(III) cluster with 2-(hydroxy-meth-yl)pyridine ligands.

In the title compound, tetra-kis[µ(3)-(2-pyrid-yl)methano-lato]tetra-kis[bromido(methanol)cobalt(III)] tetra-bromide 2-(hydroxy-meth-yl)pyridine tetra-solvate dihydrate, [Co(4)Br(4)(C(6)H(6)NO)(4)(CH(3)OH)(4)]Br(4)·4C(6)H(7)NO(4)·2H(2)O, the cation comprises a [Co(4)O(4)] cubane-type core ( symmetry). The four Co(III) ions and bridging O atoms from four (2-pyrid-yl)methano-late anions are located at alternating vertices of the cube, with bromide ions and methanol ligands on the exterior of the core, completing a distorted octa-hedral geometry. The structure is stablized by inter-molecular O-H⋯Br and O-H⋯O inter-actions.

Ligand-to-metal ratio controlled assembly of nanoporous metal-organic frameworks.

Two bilayered metal-organic frameworks with nanoporous channels were synthesized at different ligand-to-metal ratios, which demonstrated an interesting crystal-to-crystal transformation property and a special fluorescent response to the different guest molecules included.

Base-Promoted Decarboxylative Azo-Coupling: Construction of Unsymmetrical Azocarboranes.

Base-promoted decarboxylative azo couplings of carboranyl carboxylic acids with diazo salts have been developed to provide trans-azocarboranes in high yields (up to 94%). This approach is simple, efficient, and compatible with various functional groups. Mechanistically, the coupling has been proven to proceed in a nonradical pathway, which is distinct from those classical decarboxylative couplings.

Pyridyl-Directed Cp*Rh(III)-Catalyzed B(3)-H Acyloxylation of o-Carborane.

An efficient pyridyl-directed Rh(III)-catalyzed o-carborane B(3)-H acyloxylation is reported. The B(3)-H bond is the most electron-deficient vertex on o-carborane whose functionalization is challenging. The combination of Cu(OH)2 and diverse carboxylic acids provides low cost and abundant acyloxyl sources which could lead to moderate to excellent yields.

Visible-Light-Induced Cascade Reaction of Isocyanides and N-Arylacrylamides with Diphenylphosphine Oxide via Radical C-P and C-C Bond Formation.

An effective photoredox-mediated tandem phosphorylation/cyclization reaction of diphenylphosphine oxide with three types of radical acceptors leads to P(O)Ph2-containing phenanthridines, isoquinolines, and indolin-2-ones by formation of both C-P and C-C bonds. [Ir(ppy)2(dtbpy)]PF6 (1 mol %) was used as the catalyst, CsF or Cs2CO3 as the base, and K2S2O8 as the oxidant. A series of functional groups can be tolerated at room temperature. Moderate to good yields were generated.

Preparation and electrochemistry of azobenzene self-assembled monolayers on gold--long range tunneling and end-group hydrogen bonding effect.

A series of thiol-functionalied azobenzene derivatives (RAzoCnSH: R=H for n=3-6, abbreviated as AzoCnSH; R=CH(3)CONH for n=4, abbreviated as aaAzoC4SH) on gold electrodes were prepared and their self-assembly and electrochemical properties were studied by cyclic voltammetry. They all formed uniform and reproducible self-assembled monolayers (SAMs) on gold and showed well-behaved voltammetric responses in aqueous solution. Both the length of the alkyl chain spacer and the H-bonding of the end acetamino group had effects on the stability and the electrochemical kinetics of the SAMs, and the effect of the H-bonding was dominant. The surface coverage of the SAMs (AzoCnSH) is gradually increased with an increase of the alkyl chain spacer length, whereas the presence of the terminal acetamino group leads to a greater increase of the surface coverage. At a low scan rate, voltammetric responses corresponding to an irreversible two-electron, two-proton reduction/oxidation of the trans-azobenzene redox center were obtained in the range of +300 mV and -800 mV, which exhibited very large peak-to-peak splitting. At a high scan rate of 500 mV/s, two steps of reversible one-electron, one-proton reduction/oxidation corresponding to the cis-isomer in azobenzene-thiol SAMs (n is odd) was clearly observed between +300 and -200 mV. The apparent electron-transfer rate is decreased with increasing distance between the azobenzene redox center and the gold electrode. The existence of the end acetamino group which restricted the conformational change during the redox process also led to a decrease of the standard rate constant, and this restriction effect is more predominant than the distance effect.

Self-assembly of L-cysteine-copper(II)/copper(I) multilayer thin films on gold.

Self-assembled multilayer thin films have been prepared on Au substrate by alternate surface derivatization with L-cysteine hydrochloride and cupric perchlorate. The layer-by-layer structure at each step of multilayer formation was investigated by X-ray photoelectron spectroscopy. The measurements indicate that there are two structure modes in the multilayers. One is that Cu(2+) sandwiches between two amino acid groups. The other one is that Cu(+) is bonded through disulfide and thiolate. This process is also confirmed by cyclic voltammetry of Cu ion at different self-assembled multilayers. Steps further on will lead to repeated multilayer films.

Study on self-assembled monolayers of functionalized azobenzene thiols on gold: XPS, electrochemical properties, and surface-enhanced Raman spectroscopy.

Self-assembled monolayers (SAMs) of 4-acetamino-4'-(4-mercaptobutoxy)azobenzene (CH3)CONH-ph-N=N-ph-O(CH2)(4)SH, abbr. aaAzoC4SH) and 4-mercaptobutoxy azobenzene (ph-N=N-ph-O(CH2)(4)SH, abbr. AzoC4SH) on a gold surface have been studied by X-ray photoelectron spectroscopy (XPS), FT Raman spectroscopy, and electrochemistry. A surface-enhanced Raman scattering (SERS)-active system with a "sandwiched" structure of Ag/R-Azo-C4S-/Au was conveniently obtained by the method of Tollen's test. The relationship between the SERS effect and the structural nature of the system indicates that the enhancement correlates to both the silver islands above and the gold substrate underneath. The redox behaviors of the self-assembly on gold electrodes showed that the SAMs of the two compounds exhibit well-behaved voltammetric responses in a Britton-Robinson buffer corresponding to the irreversible two-electron, two-proton reduction-oxidation of azobenzene. The apparent electron-transfer rate kinetics is very sluggish, and the rate constant k(app) of aaAzoC4SH/Au (1.34 x 10(-6) s(-1)) is lower than that of AzoC4SH/Au (1.63 x 10(-4) s(-1)), which may be attributed to the different spatial restriction of close-packing structures on the conformational change accompanied by electron and proton transfer in the SAMs.

Structural, morphological, and magnetic study of nanocrystalline cobalt-nickel-copper particles.

Nanocrystalline Co(x)Ni(y)Cu(100-x-y) particles were synthesized by the reduction of metal acetates in a mixture of polyol and Tween 80. Inductively coupled plasma (ICP) analysis revealed that the actual wt% of Co, Ni, and Cu in these nanoparticles was nearly the same as in the starting solutions. The structures of the particles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED) spectroscopy, and vibrating sample magnetometry (VSM). The results of XRD and VSM confirmed that there was no metastable alloying in the particles. The particles were composites, consisting of nanoscale crystallites of face-centered cubic (fcc) Cu, face-centered cubic (fcc) Ni, and face-centered cubic (fcc) Co. During preparation the nucleation of Cu occurred first; then small Cu nuclei acted as cores for the precipitation of Co and Ni. The particles showed an increase in saturation magnetization (M(s)) as the concentration of Co or Ni in the particles was increased. The changes of both M(s) and coercivity of the particles with increasing annealing temperatures were studied. The coercivity of the particles was very high; it could reach as high as 489 Oe for Co34.3Ni31.2Cu34.5) .

Surface-enhanced Raman scattering (SERS) from different azobenzene self-assembled monolayers and sandwiches.

Self-assembled monolayers (SAMs) of functionalized azobenzene thiols (RAzoCnSH, n=3-6 for R=H, abbreviated as AzoCnSH; and n=4 for R=CH(3)CONH, abbreviated as aaAzoC4SH) on different substrates RAzoCnSz.sbnd;z.sfnc;S (S represents substrates of vacuum-deposited gold (Au), silver foil (Ag), HNO(3) etched silver foil (EAg), and silver mirror (mAg)) have been studied by SERS in the near-infrared region. SERS of the SAMs on EAg and/or mAg exhibit SERS effects that vary with etching time and/or deposition time. The most appropriate time is 5 s for etching in 1:1 HNO(3) and 40 s for deposition in 0.1 M Ag(NH(3))(2)NO(3). Further, a layer of Ag mirror was conveniently deposited on the top of the SAMs on different substrates, yielding a more efficient SERS-active system possessing a "sandwiched" structure of mAgz.sfnc;RAzoCnS-z.sfnc;S. An appropriate surface roughness is required for the strongest SERS effect. Scanning electron microscopy (SEM) indicates that there exist a large number of projects around 100 nm on the surface showing the strongest SERS effect. When the surface roughness is decreased or increased, the SERS effect decreases sharply. The relationship between the SERS effect and the structural nature was investigated and showed that the enhancement factor decays exponentially with increasing in distances of the azobenzene group from the underlying substrate or the overlying silver mirror. This result reveals that the SERS effect may be the result of the electromagnetic coupling effect between two metal layers.

[Surgical treatment of orbital and periorbital fibrous dysplasia].

OBJECTIVE: To explore the surgical approaches to obtain good aesthetic and functional results in the management of orbital and periorbital fibrous dysplasia and related deformities. METHODS: Ten cases of orbital and periorbital fibrous dysplasia were treated surgically. The location, extension and shape of the lesions were identified based on X-ray examination and two and three dimensions CT examinations preoperatively. According to the type of the lesion, different approaches were used to excise the lesion and to reconstruct the orbit. The lesions were radically or partially excised through bicoronal, intraoral and subciliary approach; the orbit was reconstructed with autogenous outer or inner table of calvarium, outer table of mandible, Medpor and prefabricated individual titanic implants. RESULTS: In 10 cases treated surgically, radical excision was employed in 4 cases and partial excision in 6 cases. Autogenous inner table of calvarium was used in 2 cases, Medpor in 2 cases, outer table of mandible in 1 case, and titanic meshwork and prefabricated individual titanic implants in 4 cases to reconstruct the orbit. After the treatment, all patients obtained satisfactory aesthetic and functional results. CONCLUSIONS: Carefully planed surgical approaches with methods for preventing the complications can be used for the treatment of orbital and periorbital fibrous dysplasia and obtaining satisfactory aesthetic and functional results.

Co(II) and Ni(II) complexes based on anthraquinone-1,4,5,8-tetracarboxylic acid (H4AQTC): canted antiferromagnetism and slow magnetization relaxation in {[Co2(AQTC)(H2O)6]·6H2O}.

Three coordination polymers {[Co2(AQTC)(H2O)6]·6H2O}n (1), {[M2(AQTC)(bpym)(H2O)6]·6H2O}n (M = Co(2), Ni(3)) have been synthesized and structurally characterized, where H4AQTC is anthraquinone-1,4,5,8-tetracarboxylic acid and bpym is 2,2'-bipyrimidine. Complex 1 features a 3-D structure, where layers of Co2(AQTC) are cross-linked by Co-H2O chains. Complexes 2 and 3 are isostructural and display 1-D chain structures. The chains are connected through hydrogen-bonding interactions to form 3-D supramolecular structures. Magnetic properties of these complexes are investigated. Compound 1 shows canted antiferromagnetism and slow relaxation below 4.0 K. For complexes 2 and 3, dominant antiferromagnetic interactions are observed. The luminescent properties of the three complexes are investigated as well.

[Study on electroacupuncture improving the single-foot supporting phase rate of stroke patients].

OBJECTIVE: To provide biomechanics basis for acupuncture improving motor function of stroke patients. METHODS: With randomized controlled trial method, 21 cases were randomly divided into a control group (n = 10) and an acupuncture group (n = 10). The control group was only treated with basic neurology therapies, and acupuncture at Shenshu (BL 23), Qihaishu (BL 24), Dachangshu (BL 25) and Pishu (BL 20) etc. were added in the acu-puncture group. After treatment for 2 weeks, the scores of Fugl-Meyer (lower limb part) and Barthel Index assessment before and after treatment were compared, and the changes of the single-foot supporting phase rate were observed. RESULTS: After treatment, the scores of Fugl-Meyer (lower limb part) and Barthel Index assessment had no significant difference in the two groups as compared with those before treatment (P > 0.05), and the single-foot supporting phase rate in acupuncture group had very significant improvement as compared with both those before treatment and those in the control group (P < 0.05 and P < 0.01, respectively). CONCLUSION: Acupuncture can increase the single-foot supporting phase rate of stroke patients and the biomechanics assessment is more sensitive than the rehabilitation scale assessment.

[3-dimensional finite elements vitodynamics analysis for mandible after mandibular angle osteotomy].

OBJECTIVE: To investigate the changes of mandibular vitodynamics in powerful bite working condition and impact working condition after mandibular angle osteotomy through 3-dimensional finit element analysis. METHODS: A patient of prominent mandibualr angle without malocclusion was selected and underwent 3-dimensional CT before and after operation. The DICOM data of 3-dimensional CT were read by Mimics software and 3-dimensional images were reconstructed. Then the 3-dimensional images were changed into IGES format and imported into ANSYS10.0. The boundary constrained condition and pre-processing condition was setting in ANSYS10.0 software. The 3-dimensional finite element models were generated in ANSYS10.0. Solution process was running and most powerful bite working condition and impact working condition were simulated and calculated. RESULTS: In static stress analysis, the stress peak and stress maximal value point of mandible were basically at equal pace in preoperative and postoperative models. In transience dynamic stress analysis, although stress discrepancies were found in part time point and some region of mandible between preoperative model and postoperative model, the direction and topography of main stress were basically at equal pace. Main stress distributed beside external oblique line and concentrates at the neck of condyle. There was no significant difference of stress conduction and distribution between preoperative and postoperative models. CONCLUSIONS: Compared with preoperative model, postoperative model has different transduction phases of stress, but has almost the same tolerance extents of main stress.

[3-dimensional CT cephalometry before and after mandibular angle osteotomy and its clinical significance].

OBJECTIVE: To investigate the change of skeleton structure and masseter after mandibular angle osteotomy and its clinical significance in preoperative design. METHODS: 3-dimensional CT cephalometry was performed before and after surgery in 18 cases of prominent mandibular angle. RESULTS: Pre- and post-operative data were compared. Significant differences between the pre- and post-operative data were found in the mandibular angle, the distance between mandibular angle, length of ramus, ectropion angle of mandibular angle, triangle Go-Me-Go, the thickness, width and length of masseter. CONCLUSIONS: It indicates the skeleton structure is changed and some kind of atrophy happens in the masseter after operation. So we suggest partial resection of masseter should be unnecessary for mandibular angle osteotomy.

[Experiment of using distraction osteogenesis to repair skull defect].

OBJECTIVE: To explore the possibility of using distraction osteogenesis to repair skull defect. METHODS: 17 goats with one year age were chosen randomly. The animals were divided to 3 groups. Group A includes 7 goats, a 3.0 cm x 2.2 cm rectangle skull defect is created on both sides of parietal area. Group B includes 5 goats, a 2.2 cm x 2.2 cm square skull defect was created on right side of parietal area. Group C includes 5 goats, a 3 cm x 1 cm rectangle skull defect was created on both sides of parietal area. Accordingly, different size of transport discs were created on right side of skull and the distraction apparatus is implanted. 3-D CT was done to measure the skull defect on group A. Biomechanical test was done on group B. Process of bone formation illustrated by histological stain, scan and transparent electric microscope was observed on group C. RESULTS: Group A measured by 3-D CT showed that skull defect of experimental side have been repaired by distraction osteogenesis. There was definitely difference between experimental and control side (P < 0.01). Group B measured by biomechanical test showed no definitely difference between experimental and normal side (maximum load P = 0.235 > 0.05, rigidity P = 0.213 > 0.05). Group C showed that the process of bone formation was typical intramembranous. CONCLUSIONS: The evidence showed that skull defect of goat can be repaired by distraction osteogenesis.