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- Octacoordinate metal carbonyls of scandium and yttrium: theoretical calculations and experimental observation. [Journal Article]
- Rapid Commun Mass Spectrom 2013 Jun 30; 27(12):1403-9.
The transition metal carbonyls are among the most important complexes in coordination chemistry. The maximum coordination number in these complexes is seven. Because the cations Sc(+) and Y(+) have empty second outermost d orbital subshells, they can possibly bond eight CO ligands, forming the 18-electron d(10) s(2) p(6) noble gas configuration. The aim of this study is to determine whether the octacoordinate metal carbonyls of Sc(+) and Y(+) exist.The structures and bonding of M(CO)n (+) (M = Sc and Y, n = 7-9) were studied using Density Functional Theory (DFT) calculations with the functionals of B3LYP and BP86. The cationic complexes from laser ablation of Sc and Y in CO gas were analyzed by time-of-flight mass spectrometry.The structures of M(CO)n (+) (M = Sc and Y, n = 7-9) and the bond dissociation energies for the last CO ligand in M(CO)n (+) (M = Sc and Y, n = 8 and 9) were obtained using DFT calculations. The products in the experiment for both metals include the series MO(CO)n (+) , MO(H2 O)(CO)n (+) and M(CO)n (+) (M = Sc or Y). The intensities of the MO(CO)n (+) and MO(H2 O)(CO)n (+) ions change gradually with the number of CO ligands, while most M(CO)n (+) ions are very weak except for three intense ones, Sc(CO)7 (+) , Sc(CO)8 (+) and Y(CO)8 (+) .Comparisons between the theoretical calculations and the experimental observations indicate that eight CO ligands are chemically bonded on the central atom in the singlet state of Sc(CO)8 (+) ((1) A1 state of D4d symmetry) and the singlet and triplet states of Y(CO)8 (+) ((1) A1 state of D4d symmetry and (3) A1g state of Oh symmetry). The (1) A1 states of both Sc(CO)8 (+) and Y(CO)8 (+) have the 18-electron d(10) s(2) p(6) noble gas configuration. In M(CO)9 (+) (M = Sc or Y), the ninth CO is weakly adsorbed on the external shell. Copyright © 2013 John Wiley & Sons, Ltd.
- Highly Stereoselective Conjugate Addition and α-Alkynylation Reaction with Electron-Deficient Alkynes Catalyzed by Chiral Scandium(III) Complexes. [JOURNAL ARTICLE]
- Chemistry 2013 May 13.
The highly Z-selective asymmetric conjugate addition of 3-substituted oxindoles to alkynyl carbonyl compounds has been developed by using scandium complexes of chiral N,N'-dioxides under mild conditions. The thermodynamically unstable Z-olefin derivatives were obtained in excellent yields and high enantiomeric and geometric control. The catalyst was also found to be effective in the asymmetric acetylenic substitution reaction of 3-substituted oxindoles, giving excellent enantioselectivities.
- Chameleon Behavior of The First Nitrilimine Scandium Derivative. [JOURNAL ARTICLE]
- J Am Chem Soc 2013 May 9.
The synthesis, structural characterization and reactivity studies of the first example of scandium substituted nitrilimine is presented. This unique complex is highly thermal stable but shows a rich reactivity to a variety of unsaturated substrates, including aldehyde, ketone, nitrile, and allene derivatives. The versatility of the complex has been further highlighted by DFT mechanistic studies.
- The effect of Er,Cr:YSGG laser irradiation on titanium discs with microtextured surface morphology. [JOURNAL ARTICLE]
- Lasers Med Sci 2013 May 7.
Both mechanical and chemical methods can be used to clean and decontaminate implant surfaces. Incomplete debridement of infected tissue and failure to clear endotoxins can result in graft failure and a return of the defect. Recently, lasers have gained popularity for sterilizing and cleaning implant surfaces. We determined the effects of laser treatment on the surface characteristics of titanium discs with a Laser-Lok surface. The discs were irradiated with an erbium, chromium: yttrium, scandium, gallium, garnet (Er,Cr:YSGG) laser under various conditions (R1-9). Scanning electron microscopy was used to evaluate the surface. Considerable surface alterations such as melting and flattening were seen at R6 (2 W, 20 Hz, 4 mm, 45 s) and R8 (3 W, 25 Hz, 2 mm, 45 s). In addition, cracking was seen at R8. The laser parameters should be optimized to conserve surface characteristics during the irradiation of implant surfaces.
- Carbide Cluster Metallofullerenes: Structure, Properties, and Possible Origin. [JOURNAL ARTICLE]
- Acc Chem Res 2013 May 1.
Endohedral metallofullerenes (EMFs) are hybrid molecules with different metallic species encapsulated inside the fullerene cages. In addition to conventional EMFs that contain only metal ions, researchers have constructed novel compounds that encapsulate metallic clusters of nitride, carbide, oxide, cyanide, and sulfide. Among these structures, carbide cluster metallofullerenes (CCMFs) are unique because their synthesis requires only graphite and the metal source. As a result the molecular structures of CCMFs are particularly difficult to characterize. Two carbon atoms are encapsulated inside the cage, but they do not participate in constructing the cage framework. Recent X-ray crystallographic studies of EMFs have allowed researchers to unambiguously identify CCMFs (MxC2@C2n). Previously most of these structures had been described as conventional EMFs Mx@C2n+2. Most of these species are scandium-containing compounds such as Sc3C2@Ih(7)-C80 [not Sc3@C3v(7)-C82], Sc2C2@C2v(5)-C80 [not Sc2@C82], Sc2C2@Cs(6)-C82 [not Sc2@Cs(10)-C84], Sc2C2@C2v(9)-C82 [not Sc2@C2v(17)-C84], Sc2C2@C3v(8)-C82 [not Sc2@D2d(23)-C84], and Sc2C2@D2d(23)-C84 [not Sc2@C86]. Additional examples of CCMFs include Gd2C2@D3(85)-C92, Sc2C2@C2v(6073)-C68, Ti2C2@D3h(5)-C78, M2C2@C3v(8)-C82, M2C2@Cs(6)-C82 (M = Y, Er, etc.), Y2C2@C84, Y2C2@D3(85)-C92, Y2C2@D5(450)-C100, and Lu3C2@D2(35)-C88. The existence of so many CCMF species reminds us that the symbol '@' (which denotes the encapsulation status of EMFs) should be used with caution with species whose molecular structures have not been determined unambiguously. This Account presents a detailed summary of all aspects of CCMFs, including historically erroneous assignments and corrected structural characterizations, along with their intrinsic properties such as electrochemical and chemical properties. We emphasize structural issues, features that are fundamental for understanding their intrinsic properties. Finally, we discuss the formation mechanism and possible origin of cluster EMFs, not just CCMFs.
- Folate-Based Radiotracers for PET Imaging-Update and Perspectives. [Journal Article]
- Molecules 2013; 18(5):5005-31.
The folate receptor (FR) is expressed in many tumor types, among those ovarian and lung cancer. Due to the high FR affinity of folic acid, it has been used for targeting of FR-positive tumors, allowing specific delivery of attached probes to the malignant tissue. Therefore, nuclear imaging of FR-positive cancer is of clinical interest for selecting patients who could benefit from innovative therapy concepts based on FR-targeting. Positron emission computed tomography (PET) has become an established technique in clinical routine because it provides an increased spatial resolution and higher sensitivity compared to single photon emission computed tomography (SPECT). Therefore, it is of critical importance to develop folate radiotracers suitable for PET imaging. This review article updates on the design, preparation and pre-clinical investigation of folate derivatives for radiolabeling with radioisotopes for PET. Among those the most relevant radionuclides so far are fluorine-18 (t1/2: 110 min, Eavβ+: 250 keV) and gallium-68 (t1/2: 68 min, Eav β+: 830 keV). Recent results obtained with new PET isotopes such as terbium-152 (t1/2: 17.5 h, Eβ+: 470 keV) or scandium-44 (t1/2: 3.97 h, Eav β+: 632 keV) are also presented and discussed. Current endeavors for clinical implementation of PET agents open new perspectives for identification of FR-positive malignancies in patients.
- Multicomponent Solvent-Free Synthesis Of Benzimidazolyl Imidazo[1,2-a]-pyridine Under Microwave Irradiation. [JOURNAL ARTICLE]
- ACS Comb Sci 2013 Apr 17.
A novel one-pot, three-component reaction employing variously substituted benzimidazole-linked amino pyridines, aldehydes, and isonitriles catalyzed by scandium(III) triflate under solvent-free conditions were accomplished. This new synthetic methodology facilitates the rapid generation of intricate molecular frameworks in three-dimensional fashion leading to benzimidazole-imidazo[1,2-a] pyridines. This approach is envisioned as an environmentally benign process and a simple operation to the biological interesting compounds. The present synthetic sequence permits the introduction of three points of structural diversity to expand chemical space with high purity and excellent yields.
- Direct and selective production of propene from bio-ethanol on sc-loaded in2 o3 catalysts. [Journal Article]
- Chemistry 2013 May 27; 19(22):7214-20.
Propene, one of key building blocks for manufacturing plastics and chemicals, could be directly and stably produced from ethanol in good yields. The conversion degree of ethanol to propene reached approximately 60 mol % by using a 3 atom % scandium-loaded indium oxide catalyst at 823 K in the presence of water and hydrogen. The introduction of Sc prevented the reduction of In2 O3 to In metal during the reaction, and that of water decreased the coke formation. Both additions resulted in longer lifetimes of the catalysts. The hydrogen addition increased the conversion of acetone to propene. The reaction pathways are also suggested on the basis of the product distributions and the pulse experiments, ethanol→acetaldehyde→acetone→propene, which is quite different from the shape-selective catalysis on zeolites and the dimerization-metathesis of ethene on nickel ion-loaded silica catalysts.
- Analysis of reserve pit sludge from unconventional natural gas hydraulic fracturing and drilling operations for the presence of technologically enhanced naturally occurring radioactive material (TENORM). [Journal Article]
- New Solut 2013; 23(1):117-35.
Soil and water (sludge) obtained from reserve pits used in unconventional natural gas mining was analyzed for the presence of technologically enhanced naturally occurring radioactive material (TENORM). Samples were analyzed for total gamma, alpha, and beta radiation, and specific radionuclides: beryllium, potassium, scandium, cobalt, cesium, thallium, lead-210 and -214, bismuth-212 and -214, radium-226 and -228, thorium, uranium, and strontium-89 and -90. Laboratory analysis confirmed elevated beta readings recorded at 1329 ± 311 pCi/g. Specific radionuclides present in an active reserve pit and the soil of a leveled, vacated reserve pit included 232Thorium decay series (228Ra, 228Th, 208Tl), and 226Radium decay series (214Pb, 214Bi, 210Pb) radionuclides. The potential for impact of TENORM to the environment, occupational workers, and the general public is presented with potential health effects of individual radionuclides. Current oversight, exemption of TENORM in federal and state regulations, and complexity in reporting are discussed.
- Evaluation of microleakage of root canal fillings irradiated with different output powers of erbium, chromium:yttrium-scandium-gallium-garnet laser. [Journal Article]
- Aust Endod J 2013 Apr; 39(1):8-14.
This study evaluated the root canal seal achieved by irradiation with an erbium, chromium:yttrium-scandium-gallium-garnet laser, and the optimal output power to remove debris and the smear layer were determined. One hundred mandibular premolar teeth were prepared and divided into four groups. Group 1 was not lased but was irrigated with 5 mL of 5.25% NaOCl and 5 mL of 17% ethylenediaminetetraacetic acid. Group 2 was irradiated at a panel setting of 1 W, group 3 at 2 W and group 4 at 2.5 W, with a 50% water level and 48% air-cooling level. Root canals were obturated by cold lateral compaction, and apical microleakage was measured using a fluid filtration model. The remaining debris and smear layer were evaluated via scanning electron microscopy. Statistically significant differences were detected between groups. Irradiation at 1 and 2 W using an erbium, chromium:yttrium-scandium-gallium-garnet laser produced a seal superior to that of the other treatments.