title: Communications: Chain and double-ring polymeric structures: Observation of Al(n)H(3n+1) (-) (n=4-8) and Al(4)H(14) (-).
abstract: A pulsed arc discharge source was used to prepare gas-phase, aluminum hydride cluster anions, Al(n)H(m) (-), exhibiting enhanced hydrogen content. The maximum number of hydrogen atoms in Al(n)H(m) (-) species was m=3n+1 for n=5-8, i.e., Al(n)H(3n+1) (-), and m=3n+2 for n=4, i.e., Al(4)H(14) (-), as observed in their mass spectra. These are the most hydrogen-rich aluminum hydrides to be observed thus far, transcending the 3:1 hydrogen-to-aluminum ratio in alane. Even more striking, ion intensities for Al(n)H(m) (-) species with m=3n+1 and m=3n+2 hydrogen atoms were significantly higher than those of nearby Al(n)H(m) (-) mass peaks for which m<3n+1, i.e., the ion intensities for Al(n)H(3n+1) (-) and for Al(4)H(14) (-) deviated from the roughly bell-shaped ion intensity patterns seen for most Al(n)H(m) (-) species, in which m ranges from 1 to 3n. Calculations based on density functional theory showed that Al(n)H(3n+1) (-) clusters have chain and/or double-ring polymeric structures.
authors.affiliation: Department of Chemistry and Department of Materials Science, Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: Xiang
authors.initials: X
authors.lastname: Li
authors.forename: Andrej
authors.initials: A
authors.lastname: Grubisic
authors.forename: Kit H
authors.initials: KH
authors.lastname: Bowen
authors.forename: Anil K
authors.initials: AK
authors.lastname: Kandalam
authors.forename: Boggavarapu
authors.initials: B
authors.lastname: Kiran
authors.forename: Gerd F
authors.initials: GF
authors.lastname: Gantefoer
authors.forename: Puru
authors.initials: P
authors.lastname: Jena