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New Precursors (new + precursor)
Selected AbstractsHeteroleptic Guanidinate- and Amidinate-Based Complexes of Hafnium as New Precursors for MOCVD of HfO2EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 11 2010Ke Xu Abstract The synthesis and characterization of four new heteroleptic complexes [Hf{,2 -(iPrN)2CNMe2}2Cl2] (1), [Hf{,2 -(iPrN)2CNMe2}2Me2] (2), [Hf{,2 -(iPrN)2CMe}2Cl2] (3), and [Hf{,2 -(iPrN)2CMe}2Me2] (4) are reported. All the complexes were characterized by spectroscopic methods, while compounds 1,3 were further examined by single-crystal X-ray diffraction, revealing that the complexes are monomers with the hafnium center in a distorted octahedral geometry. The thermal properties of the chlorine-free complexes (2, 4) were examined to determine their suitability for metalorganic chemical vapor deposition (MOCVD) applications, and compound 2 showed good volatility and thermal stability. On the basis of these results, compound 2 was selected for MOCVD of HfO2 with oxygen as oxidant. Depositions were carried out on Si(100) substrates in the temperature range 300,700 °C. The as-deposited HfO2 films crystallized in the monoclinic phase at temperatures above 500 °C, and the composition analysis determined by Rutherford back-scattering (RBS) and X-ray photoelectron spectroscopy (XPS) revealed that the films were stoichiometric and free of carbon. Thus, alkylguanidinatohafnium complex 2 is a promising precursor for growing HfO2 films in a wide temperature range with the desired stoichiometry, because of its adequate volatility, sufficient temperature window between vaporization and decomposition, as well as its ability to decompose cleanly in the presence of oxygen. [source] Expanded Radialenes with Bicyclo[4.3.1]decatriene Units: New Precursors to Cyclo[n]carbons.CHEMINFORM, Issue 6 2004Yoshito Tobe No abstract is available for this article. [source] New precursors for hexanitrohexaazaisowurtzitane (HNIW, CL-20)JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2000Kyoo-Hyun Chung Two new polyacylhexaazaisowurtzitanes were synthesized. Pentaacetyl- or pentaacetylformylhexaazaisowurtzitane can be a precursor in the preparation of HNIW, recently developed highly energetic material. [source] Simple and high radiochemical yield synthesis of 2,-Deoxy-2,-[18F]fluorouridine via a new nosylate precursorJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2006Se Hun Kang Abstract We synthesized 2'-deoxy-2'-[18F]fluorouridine (7) as a radiotracer for positron emission tomography from a new nosylate precursor (6). This new precursor was synthesized from uridine in four steps. The overall synthetic yield was 9.4% and we have high stability of >98% purity up to 6 months at 4°C. The optimal manual [18F]fluorination conditions were 30 mg of the precursor 6 in 500 µl of acetonitrile at 145°C for 15 min with 370 MBq of [18F]fluoride. The [18F]fluorination yield was 76.5±2.7% (n = 3). After hydrolysis of protecting groups with 1 N HCl and purification by HPLC, the overall radiochemical yield and purity were 26.5±1.4% and 98.2±2.5%, respectively. The preparation time was 70.0±10.5 min (n = 3 for each result). We also developed an automated method with a radiochemical yield and purity of 24.0±2.8 and 98.0±1.5% (n = 10) using a GE TracerLab MX chemistry module. This new nosylate precursor for 2'-deoxy-2'-[18F]fluorouridine synthesis showed higher radiochemical yields and reproducibility than previous methods. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||