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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. January 2004, Volume 3, Number 1, 1-10 |
Interconversion of Singlet Indium Subhydride Isomers: Theoretical Study
Jerzy Moc and Maria Wierzejewska
Internet Electron. J. Mol. Des. 2004, 3, 1-10
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Abstract:
The recent matrix isolation infrared (IR) studies by Downs
and co-workers reported the detection of some indium
subhydride In2H2 isomers.
The dibridged isomer 1 and trans
isomer 3 were identified, whereas the experimental IR
spectra did not provide any indication of other plausible
singlet isomers: branched 2 and monobridged 4. In order to
shed more light on the rearrangement barrier heights and
related kinetic stability of various forms of In2H2 we have
undertaken quantum-chemical study of the isomerization and
dissociation pathways and IR spectra of this elusive
main-group heavy metal hydride. Density functional theory (DFT)
with B3LYP functional and ab initio second-order
Møller-Plesset (MP2) perturbation theory were used for structure
determination, whereas energetics was evaluated by means of
coupled-cluster singles and doubles method incorporating a
perturbative correction for triples (CCSD(T)). For indium,
Wadt and Hay (WH), Stevens, Basch, Krauss and Jasien
(SBKJ) and Stuttgart-Dresden-Bonn (SDB) relativistic
effective core potentials (ECP) were employed in conjunction
with the appropriate valence basis sets to examine the effect
of the ECP/basis on the results. The reaction pathways for the
interconversion of the four isomers 1-4
of In2H2 have been
calculated and the results compared with the experimental
data. The lowest energy rearrangement of the most stable
dibridged isomer 1 into the branched 2 and trans 3 isomers
occurs via the two step mechanism with the monobridged
species 4 involved as the intermediate and the corresponding
energy barriers lying in the range ca. 16-20 kcal/mol relative
to 1.
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