Page 298 - Academic Press Encyclopedia of Physical Science and Technology 3rd InOrganic Chemistry

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Encyclopedia of Physical Science and Technology EN010H-470 July 16, 2001 16:53

Nanosized Inorganic Clusters 307

n t
Ag 114 Se 34 (Se Bu) 46 P Bu 3
14
t
P Bu 3
n
Ag(C 11 H 23 CO 2 ) + BuSeSiMe 3
dppp

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Ag 172 Se 40 (Se Bu) 92 (dppp) 4
SCHEME 3 Synthetic route to the Ag 114 and the Ag 172 clusters.

III. FROM BUILDING BLOCKS
VIA CLUSTERS TO SOLIDS

The one-pot synthesis of ring-shaped and spherical poly-
oxometalates, based on a set of structurally conserved
building blocks, has been another highly successful route
to clusters of nanoscopic dimensions containing cavities
and, in principle, pores. Such syntheses have been found
to be based upon a building block principle with units that
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FIGURE 5 Se skeleton in [Ag 90 Se 38 (Se Bu) 14 (PEt 3 ) 22 ]. Se are suggested to have intrinsic properties (variable charge
and flexible coordination modes) that facilitate the self-
atoms are shown by the horizontally hatched spheres and
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the Se atoms of the Se Bu groups as diagonally hatched assembly of clusters containing many thousands of atoms
in solution (Fig. 9). In this respect, the use of pentagonal-
spheres.
type building groups, with different symmetries, plays a
key role in the formation of these systems as pentagonal
units allow the construction of clusters with curvature that
in turn prevents immediate growth to bulk materials.

n
n
FIGURE 6 Molecular structure of [Ag 114 Se 34 (Se Bu) 46 FIGURE 7 Molecular structure of [Ag 172 Se 40 (Se Bu) 92 (dppp) 4 ].
t
(P Bu 3 ) 14 ]. Ag atoms are shown as empty spheres, Se atoms Ag atoms are shown as empty spheres and Se atoms depicted
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depicted as horizontally hatched spheres, and the Se atoms of as horizontally hatched spheres, the Se atoms of the Se Bu as
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the Se Bu groups as diagonally hatched spheres. diagonally hatched spheres, and the P atoms as black spheres.