Large-scale engineered synthesis of BaTiO3 nanoparticles using low-temperature bioinspired principles.

We report here a robust, large-scale synthesis of BaTiO3 nanopowders using a bioinspired process that first was developed on a much smaller scale. The most advantageous points of this protocol are that it takes place at nearly room temperature (25°C), overcomes many limitations encountered in other scale-up processes (such as the need for external drivers, e.g., heat, radiation or pressure), bypasses the use of surfactants and templates and does not necessitate pH adjustment. The use of a single-source, bimetallic alkoxide with the vapor diffusion of a hydrolytic catalyst (H2O) provides the necessary conditions for facile crystallization and growth of small, well-defined BaTiO3 nanoparticles at mild temperatures, yielding batches of up to 250 ± 5 g in a green process. Extension of this method to kilogram-scale production of BaTiO3 nanocrystals in semicontinuous and continuous processes is feasible.

Iron phosphide nanostructures produced from a single-source organometallic precursor: nanorods, bundles, crosses, and spherulites.

Single-source molecular precursors were found to produce iron phosphide materials. In a surfactant system of trioctylamine and oleic acid, H2Fe3(CO)9PtBu reacted to form Fe4(CO)12(PtBu)2, which decomposed to give Fe2P nanorods and "bundles." Control of the morphology obtained was possible by varying the surfactant system; addition of increasing amounts of oleic acid resulted in crystal splitting, while the addition of microliter amounts of an alkane enhanced the crystal splitting to give sheaflike structures. The different morphologies seen were attributed to imperfect crystal growth mechanisms.

Adducts of thianthrene- and phenoxathiin cation radical tetrafluoroborates to 1-alkynes. Structures and formation of 1-(5-thianthreniumyl)- and 1-(10-phenoxathiiniumyl)alkynes on alumina leading to alpha-ketoylides and alpha-ketols.

[structure: see text] Thianthrene cation radical tetrafluoroborate (Th*+ BF4(-)) added to the terminal alkynes 1-pentyne, 1-hexyne, 1-heptyne, 1-octyne, 1-nonyne, and 1-decyne to form trans-1,2-bis(5-thianthreniumyl)alkene tetrafluoroborates (1-6). Similarly, addition of phenoxathiin cation radical tetrafluoroborate (PO*+ BF4(-)) to the same alkynes gave 1,2-bis(10-phenoxathiiniumyl)alkene tetrafluoroborates (7-12). The trans configuration of two of the adducts (1 and 4) was shown with X-ray crystallography. When solutions of 1-6 in chloroform were stirred with activated alumina, cis elimination of a proton and thianthrene (Th) occurred with the formation of 1-(5-thianthreniumyl)alkyne tetrafluoroborates (1a-6a). Similar treatment of 8-12 caused elimination of a proton and phenoxathiin (PO) with formation of 1-(10-phenoxathiiniumyl)alkene tetrafluoroborates (8a-12a). Stirring of 1a-6a with alumina for short periods of time caused their conversion into 5-[(alpha-keto)alkyl]thianthrenium ylides (1b-6b) and alpha-ketols, RC(O)CH2OH (1c-6c).

Adducts of thianthrene- and phenoxathiin cation radical salts with symmetrical alkynes. Structure and formation of cumulenes on alumina leading to alpha-diketones, alpha-hydroxyalkynes, and alpha-acetamidoalkynes.

[reaction: see text] Thianthrene cation radical tetrafluoroborate (Th*+ BF4-) added to 2-butyne, 3-hexyne, 4-octyne, and 5-decyne in MeCN to form trans bisadducts R(Th+)C=C(Th+)R, where R = Me, Et, Pr, Bu (7a-d). Phenoxathiin cation radical tetrafluoroborate (PO*+ BF4-) added similarly to the last three alkynes to form adducts R(PO+)C=C(PO+)R, 8b-d. Cyclic monoadducts were not found. The trans structures of 7 and 8 were deduced with X-ray crystallography (7c) and NMR spectroscopy. When solutions of adducts in CHCl3 and MeCN were deposited on activated alumina, elimination of thianthrene (Th) and phenoxathiin (PO) occurred almost quantitatively. Detailed studies with (7b-d) indicated that a cumulene (15) was formed by the elimination of Th and that 15 was subsequently converted into small amounts of other products. In CHCl3, these products were the respective alkyne, thianthrene 5-oxide, an alpha-diketone (11), an alpha-hydroxyalkyne (12), and hydrogen. The same products were formed in MeCN along with an alpha-acetamidoalkyne (13). The formation of 15 and products derived from it is explained and was confirmed by preparation and reactions of 2,3,4-hexatriene.

Decomposition of alkene adducts of thianthrene cation radical in nitrile solvents. Formation of alkyl-2-oxazolines and a new class of four-component products: 5-[(1-alkoxyalkylidene)ammonio]alkylthianthrenium diperchlorates.

The monoadducts (4a-d) of thianthrene cation radical perchlorate (1a) and isobutene, 2-methylbutene, 2-methyl-2-butene, and 2-methylpentene decompose spontaneously in acetonitrile (MeCN) solution, with the formation of thianthrene (Th). Decomposition of 4a (1,2-(5,10-thianthreniumdiyl)-2-methylpropane diperchlorate) and 4a', the corresponding dihexafluorophosphate, was studied in depth and extensively with (1)H and (13)C NMR spectroscopy. Decomposition of 4a was found to involve the solvent itself as well as water in the solvent, remaining from incomplete drying, and gave, apart from Th, successively, the perchlorate salts of 2,4,4-trimethyl-2-oxazoline (6) and 2-amino-2-methylpropyl acetate (7). These salts, 6-HClO(4) and 7-HClO(4), respectively, were prepared and used in understanding the reactions of 4a as well as the relationships among 6, 7, and 2-(acetylamino)-2-methyl propanol (8) in acidified MeCN solution. Decompositions of 4a-d in MeCN and other nitriles (RCN) containing an added alcohol (R'OH) led to new products, 5-[(1-alkoxyalkylidene)ammonio]alkylthianthrenium diperchlorates (5a-u). These compounds were identified with (1)H and (13)C NMR spectroscopy and, in part, with X-ray crystallography and elemental analysis. The mechanisms of formation of 5-7 are discussed.

Toward a general strategy for the synthesis of heterobimetallic coordination complexes for use as precursors to metal oxide materials: synthesis, characterization, and thermal decomposition of Bi(2)(Hsal)(6).M(acac)(3) (M = Al, Co, V, Fe, Cr).

Bismuth(III) salicylate, [Bi(Hsal)(3)](n), reacts readily with the trivalent metal beta-diketonate compounds M(acac)(3) (acac = acetylacetonate; M = Al, V, Cr, Fe, Co) to produce trinuclear coordination complexes of the general formula Bi(2)(Hsal)(6).M(acac)(3) (M = Al, V, Cr, Fe, Co) in 60-90% yields. Spectroscopic and single crystal X-ray diffraction experiments indicate that these complexes possess an unusual asymmetric nested structure in both solution and solid state. Upon standing in dichloromethane solution, Bi(2)(Hsal)(6).Co(acac)(3) eliminates Bi(Hsal)(3) to give the 1:1 adduct Bi(Hsal)(3).Co(acac)(3). The 2:1 heterobimetallic molecular compounds undergo facile thermal decomposition on heating in air to 475 degrees C to produce heterometallic oxide materials, which upon annealing for 2 h at 700 degrees C form crystalline oxide materials. The synthetic approach detailed here represents a unique, general approach to the formation of heterobimetallic bismuth-based coordination complexes via the coordination of M(acac)(3) complexes to bismuth(III) salicylate.