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The characterisation of molecular alkali-metal azides

The characterisation of molecular alkali-metal azides
The characterisation of molecular alkali-metal azides
Matrix isolation infrared (IR) studies have been carried out on the vaporisation of the alkali-metal azides MN3 (M = Na, K, Rb and Cs). The results show that under high vacuum conditions, molecular KN3, RbN3 and CsN3 are present as stable high-temperature vapour species, together with variable amounts of nitrogen gas and the corresponding metal atoms. The characterisation of these molecular azides is supported by ab initio molecular orbital calculations and density functional theory (DFT) calculations, and for CsN3 in particular, by the detection of the isotopomers CS((NNN)-N-14-N-15-N-14) and Cs((NNN)-N-15-N-14-N-14). The IR spectra are assigned to a "side-on" (C-2v) structure by comparison with the spectral features predicted both by vibrational analysis and calculation. The most intense IR features for KN3, RbN3 and CsN3 isolated in nitrogen matrices lie at 2005, 2004.4 and 2002.2cm(-1), respectively, and correspond to the N-3 asymmetric stretch. The N-3 bending mode in CsN3 is identified at 629 cm(-1). An additional feature routinely observed in these experiments occurred at approximately 2323 cm(-1) and is assigned to molecular N-2, perturbed by the close proximity of an alkali-metal atom. The position of this band appeared to show very little cation dependence, but its intensity correlated with the extent of sample thermal decomposition.
alkali metals, azides, ir spectroscopy, matrix isolation, theoretical calculations matrix-isolation, basis-sets, coordination, n-6, vaporization, stability, chemistry, constants, n-5(+), ion
0947-6539
3580-3586
Ogden, J. Steven
5a99fd42-75e7-4f7b-a347-ac2b1717b8b3
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Ferrante, Francesco
5b217df6-ac83-4b5d-85c3-96060e69b89a
Gagliardi, Laura
b20d2c29-eb23-4b27-bef0-9ea53ea717dc
Ogden, J. Steven
5a99fd42-75e7-4f7b-a347-ac2b1717b8b3
Dyke, John M.
46393b45-6694-46f3-af20-d7369d26199f
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Ferrante, Francesco
5b217df6-ac83-4b5d-85c3-96060e69b89a
Gagliardi, Laura
b20d2c29-eb23-4b27-bef0-9ea53ea717dc

Ogden, J. Steven, Dyke, John M., Levason, William, Ferrante, Francesco and Gagliardi, Laura (2006) The characterisation of molecular alkali-metal azides. Chemistry - A European Journal, 12 (13), 3580-3586. (doi:10.1002/chem.200501101).

Record type: Article

Abstract

Matrix isolation infrared (IR) studies have been carried out on the vaporisation of the alkali-metal azides MN3 (M = Na, K, Rb and Cs). The results show that under high vacuum conditions, molecular KN3, RbN3 and CsN3 are present as stable high-temperature vapour species, together with variable amounts of nitrogen gas and the corresponding metal atoms. The characterisation of these molecular azides is supported by ab initio molecular orbital calculations and density functional theory (DFT) calculations, and for CsN3 in particular, by the detection of the isotopomers CS((NNN)-N-14-N-15-N-14) and Cs((NNN)-N-15-N-14-N-14). The IR spectra are assigned to a "side-on" (C-2v) structure by comparison with the spectral features predicted both by vibrational analysis and calculation. The most intense IR features for KN3, RbN3 and CsN3 isolated in nitrogen matrices lie at 2005, 2004.4 and 2002.2cm(-1), respectively, and correspond to the N-3 asymmetric stretch. The N-3 bending mode in CsN3 is identified at 629 cm(-1). An additional feature routinely observed in these experiments occurred at approximately 2323 cm(-1) and is assigned to molecular N-2, perturbed by the close proximity of an alkali-metal atom. The position of this band appeared to show very little cation dependence, but its intensity correlated with the extent of sample thermal decomposition.

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Published date: 2006
Keywords: alkali metals, azides, ir spectroscopy, matrix isolation, theoretical calculations matrix-isolation, basis-sets, coordination, n-6, vaporization, stability, chemistry, constants, n-5(+), ion

Identifiers

Local EPrints ID: 44512
URI: http://eprints.soton.ac.uk/id/eprint/44512
ISSN: 0947-6539
PURE UUID: 83fedd00-2aeb-4332-a744-6a18b5e014cc
ORCID for John M. Dyke: ORCID iD orcid.org/0000-0002-9808-303X
ORCID for William Levason: ORCID iD orcid.org/0000-0003-3540-0971

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Date deposited: 06 Mar 2007
Last modified: 29 Oct 2019 02:11

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Contributors

Author: J. Steven Ogden
Author: John M. Dyke ORCID iD
Author: William Levason ORCID iD
Author: Francesco Ferrante
Author: Laura Gagliardi

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