Oligomeric Rods of Alkyl- and Hydridogallium Imides
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- 作者：Bethany L. Kormos ; Jolin A. Jegier ; Paul C. Ewbank ; Udo Pernisz ; Victor G. Young ; Jr. ; Christopher J. Cramer ; and Wayne L. Gladfelter
- 刊名：Journal of the American Chemical Society
- 出版年：2005
- 出版时间：February 9, 2005
- 年：2005
- 卷：127
- 期：5
- 页码：1493 - 1503
- 全文大小：389K
- 年卷期：v.127,no.5(February 9, 2005)
- ISSN：1520-5126
文摘
Reaction of [RGa(NMe2)2]2, where R = Me, Et, Bu, and Hx, with ammonia at 150 
C in anautoclave produced insoluble white powders formulated as oligomers of [RGaNH]n. The analogous reactionbetween NH3 and MeGa[N(SiMe3)2]2 at low temperature (<25 C) formed an isolable intermediate, [MeGa(
-NH2)N(SiMe3)2]2, that was characterized using single-crystal X-ray diffraction. Infrared spectroscopy andX-ray diffraction of the oligomers were consistent with a rodlike structure comprised of six-membered,[RGaNH]3 rings stacked perpendicular to the long axis of the rod. The method of synthesis, formula, anddiffraction results suggested a structural similarity between the alkyl, [RGaNH]n, and the previously reportedhydride, [HGaNH]n. The structural and electronic properties of rods having the general formula H3[(HXYH)3]nH3 (XY = GaN, GeC; n = 1-9) were investigated using density functional theory. Atomicelectronegativity differences between the group 13/15 and 14/14 systems were found to play importantroles in the geometrical structures of the two rods and also caused significant differences in the electronicstructures. Energetically, it was found to be increasingly favorable to add additional cyclotrigallazane ringsto the GaN rods, while for the GeC rods, there was a roughly constant energy cost associated with eachadditional ring. The electric dipole moments of the GaN rods increased substantially with length; in theGeC rods, charge separation occurred to a much smaller extent and had a polarization opposite to thatfound in GaN. In addition, increased dipole moments correlated with smaller electronic excitation energies,as predicted by time-dependent density functional theory. All of the powders exhibited luminescence in thevisible spectrum at room temperature. Structure observed in the photoluminescence spectra of [HGaNH]nand [MeGaNH]n was interpreted as arising from rods of different length.
C in anautoclave produced insoluble white powders formulated as oligomers of [RGaNH]n. The analogous reactionbetween NH3 and MeGa[N(SiMe3)2]2 at low temperature (<25 C) formed an isolable intermediate, [MeGa(-NH2)N(SiMe3)2]2, that was characterized using single-crystal X-ray diffraction. Infrared spectroscopy andX-ray diffraction of the oligomers were consistent with a rodlike structure comprised of six-membered,[RGaNH]3 rings stacked perpendicular to the long axis of the rod. The method of synthesis, formula, anddiffraction results suggested a structural similarity between the alkyl, [RGaNH]n, and the previously reportedhydride, [HGaNH]n. The structural and electronic properties of rods having the general formula H3[(HXYH)3]nH3 (XY = GaN, GeC; n = 1-9) were investigated using density functional theory. Atomicelectronegativity differences between the group 13/15 and 14/14 systems were found to play importantroles in the geometrical structures of the two rods and also caused significant differences in the electronicstructures. Energetically, it was found to be increasingly favorable to add additional cyclotrigallazane ringsto the GaN rods, while for the GeC rods, there was a roughly constant energy cost associated with eachadditional ring. The electric dipole moments of the GaN rods increased substantially with length; in theGeC rods, charge separation occurred to a much smaller extent and had a polarization opposite to thatfound in GaN. In addition, increased dipole moments correlated with smaller electronic excitation energies,as predicted by time-dependent density functional theory. All of the powders exhibited luminescence in thevisible spectrum at room temperature. Structure observed in the photoluminescence spectra of [HGaNH]nand [MeGaNH]n was interpreted as arising from rods of different length.