Polyhedral Oligomeric Silsesquioxane (POSS) cages with

Polyhedral Oligomeric Silsesquioxane (POSS) cages with
endohedral metal hydrides
Polyhedral Oligomeric Silsesquioxane (POSS)
cages are of major interest as building blocks for
nano-structured hybrid materials and
nanocomposites [1-3]. POSS molecules may be
employed to increase the interfacial area and to
tune domain distances in solar cells based on
conjugated polymers and fullerenes [1].
In this contribution, we investigate encapsulation
of metal hydrides as a means to alter the
energetic and electronic properties of three basic
POSS cages ( Tn with n = 8, 10, 12) in a controlled
way. As an additional benefit, POSS cages with
internal metal hydrides might prove to be
efficient as novel media of hydrogen storage.
AlH3 , a light metal-hydride
Xiqiao Wang, John Corn, Frank Hagelberg
Department of Physics and Astronomy
East Tennessee State University
Johnson City, TN 37614
The interaction between metal hydride cores and POSS
cages was explored by using various ab initio and
density functional theory (DFT) techniques [5], with ab
initio procedures ranging from HF (Hartree-Fock) to MP2
(Moeller-Plesset perturbation theory at second order).
PtH4 within T12
Optimization performed
using frequency analysis at
the B3LYP/CEP-31G level
A variety of metal-hydrides could be stored in T12 cages.
However, the more
conventional T8 cage is more easily fabricated.
ΔE [Hartree]
[email protected] MP2/CEP-121G
-0.024 ~ -0.030
[email protected] MP2/CEP-121G
[email protected] MP2/CEP-121G
[email protected] MP2/CEP-121G
For MHm molecules inside the T8 and T10 cages, no
stability was found for m>2 . For m=2, cage symmetry
change associated with elongation along the MH2 axis
was found to occur in T8 cage.
Some common structures of [email protected] complexes
Due to the size restriction associated with T8, no systems of
the form [email protected] with m > 2 were found to converge.
Some periodic arrangements of T8 and [email protected] were
included and proven to be stable:
FeH2 within T8
Results were found at the
HF/CEP-121G level. Geometric
optimizations were confirmed
using MP2 and B3LYP.
(left: Al crystals, right: AlH3 crystals)
Fullerene Cages
L.Gagliardi performed a computational study of
metal-hydrides encapsulated in within fullerenes,
such as ZrH16 @ C60 and 2TiH16 @ C114 [4].
Equilibrium structures were obtained for systems of the
[email protected] [(SiO3/2H)n],
with m = 2, 3, 4, n = 8, 10, 12, and M = transition metal
elements in Group IVB, VIB, VIII, IIB.
The potential surface inside the less studied T12 cage
turned out to be relatively flat, and equilibrium
geometries were obtained for a wide range of large
metal hydrides.
Support by TN-SCORE (NSF EPS 1004083)
is gratefully acknowledged.
Zero-point corrected stabilization energies ΔE for T10
based systems were found to be negative, corresponding
to an exothermal encapsulation process, in 4 cases:
• A wide variety of POSS cages with enclosed metal hydrides
were shown to be stable by ab initio computation. For RuH2,
PdH2, OsH2 , PtH2 encapsulation into T10 was found to be an
exothermal process.
• An effort to analyze POSS polymers with endohedral metal
hydrides was initialized.
[1] F.Wang, X.Lu, C.He, J.Mat.Chem. 21, 2775 (2011)
[2] D. Hossain, F.Hagelberg, C.Pittman, S.Saebo, J.Inorg.
Org.Pol.Mat. 20, 1574 (2010)
[3] D. Hossain, C. Pittman Jr., F. Hagelberg, S. Saebo,
J.Phys.Chem.C, 112, 16070 (2008)
[4] L.Gagliardi, J.Chem.Theo.Comp. 1, 1172 (2005)
[5] M.J.Frisch et al. Gaussian, Rev. B.01, Gaussian Inc.,
Wallingford, CT (2004)

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