Gallium hydride complexes stabilised by multidentate alkoxide ligands: precursors to thin films of Ga2O3 at low temperatures.
The donor-functionalised alkoxides {Me(3-x)N(CH(2)CH(2)O)(x)} (L(x); x = 1, 2) have been used to form gallium hydride complexes [{GaH(2)(L(1))}(2)] and [{GaH(L(2))}(2)] that are stable and isolable at room temperature. Along with a heteroleptic gallium tris(alkoxide) complex [Ga(L(1))(3)] and the dimeric complex [{GaMe(L(2))}(2)], these compounds have been used as single-source precursors for the deposition of Ga(2)O(3) by aerosol-assisted chemical vapour deposition (AACVD) with toluene as solvent. The resulting films were mostly transparent, indicating low levels of carbon contamination, and they were also mainly amorphous. However, [Ga(L(1))(3)] did contain visibly crystalline material deposited at a substrate temperature of 450 °C, by far the lowest ever observed for the CVD of gallium oxide.
Synthesis of group 13 sesquialkoxides and their application as precursors to crystalline oxide films
The reaction of Me3Ga with an excess of 4-methylbenzyl alcohol (4-MeC6H4CH2OH) in toluene, under reflux conditions, resulted in the formation of the sesquialkoxide [Ga{MeGa(OCH2C6H4Me-4)(3)}(3)] (1). In contrast, reaction of Me3In with excess of 4-methylbenzyl alcohol (4-MeC6H4CH2OH) under the same conditions afforded another type of sesquialkoxide, [In{Me2In(OCH2C6H4Me-4)(2)}(3)] (2). Compounds 1 and 2 have been characterized by NMR, FTIR, and elemental analysis, and the structure of 1 was determined by X-ray crystallography. The structure of 1 consists of a central Ga3+ ion coordinated by three [MeGa(OCH2C6H4Me-4)(mu-OCH2C6H4Me-4)(2)](-) units such that it has a coordination number of six. The surrounding metal ions are four coordinate. H-1 NMR data for 1 indicate that in solution two isomers (1:1) are present, namely, the C-1- and C-3-symmetrical isomers, but in the solid state 1 exists as the C-3-symmetrical isomer. Compound 1 possesses the correct ratio of Ga:O atoms (2:3) for that found in gallium oxide (Ga2O3), and LPCVD of 1 afforded crystalline Ga2O3 films at 600 degrees C. These results are surprising, as Ga2O3 films are typically only crystalline above 700 degrees C.
Determination of iodide with 1,3-dibromo-5,5-dimethylhydantoin (DBH) in comparison with the ICl-method. Analytical methods of pharmacopeias with DBH in respect to environmental and economical concern. Part 3.
USP 1995 (The United States Pharmacopeia, 23rd Edit., (1995), potassium iodide p. 1265, sodium iodide p. 1424), PH. EUR. 1997 (European Pharmacopoeia, third ed., Council of Europe, Strasbourg, (1997), potassium iodide p. 1367, sodium iodide p. 1493) and JAP 1996 (The Japanes Pharmacopoeia, 13th ed. (1996), potassium iodide p. 578, sodium iodide p. 630) determine iodide with the ICl-method (J. Am. Chem. Soc. 25 (1903) 756-761; Z. Anorg. Chem. 36 (1903) 76-83; Fresenius Z. Anal. Chem. 106 (1936) 12-23; Arzneibuch-Kommentar, Wissenschaftliche Erläuterungen zum Europäischen Arzneibuch, Wissenschaftliche Verlagsgesellschaft mbH, Stuttgart, Govi-Verlag - Pharmazeutischer Verlag GmbH, Eschborn, 12th suppl. (1999), K10 p. 2), using chloroform, which is toxic and hazardous to environment. Without the application of chlorinated hydrocarbons USP 2000 (The United State Pharmacopeia, 24th ed. (2000), potassium iodide p. 1368, sodium iodide p. 1535) and Brit 1999 (British Pharmacopoeia London, (1999), Appendix VIII C, p. A162) titrate iodide with the redox indicator amaranth. A titration with potentiometric indication giving two end-points at the step of I(2) and [ICl(2)](-) is described. Due to the high concentration of hydrochloric acid required for the ICl-method, the determination with DBH (1,3-dibromo-5,5-dimethylhydantoin; 1,3-dibromo-5,5-dimethyl-2,4-imidazolidinedione) can be recommended and is performed easily. Similarly, the iodide content of gallamine triethiodide may be analyzed with DBH by application of a visual two-phase titration in water and ethyl acetate or with potentiometric indication in a mixture of 2-propanol and water. During the removal of the excess of DBH 4-bromo-triethylgallamine (2,2',2"-[1-bromo-benzene-2,3,4-triyltris(oxy)]N,N,N-triethylethanium) is formed.