of molybdenum and oxygen atoms, the most important of which are collected in
Table 14.1, show the following characteristics:
. All listed clusters contain the fundamental pentagonal {(Mo)Mo 5 } building
block, comprising a central pentagonal bipyramidal {MoO 7 } group with six surrounding edge-sharing {MoO 6 } octahedra. These can occur in very different
environments.
. The units are, for example, central to the construction of spherically shaped
entities with positive curvatures. (Note that even the famous so-called bucky-ball
{C 60 } fullerene molecule contains 12 pentagonal ‘units’.) However, for the generation of more complex patterns, including negative as well as positive curvatures, that is showing symmetry breaking, a rather large number of negative and
positive vertices with polygons of different kinds, for example including heptagons, is necessary [4].
The highly symmetric [(pent) 12 (link) 30 ] type spherical clusters, such as the {Mo 132 }
type nanospheres (Figure 14.2, right), are comprised of 12 pentagonal {(Mo)Mo 5 }
groups (pent) connected by 30 {Mo 2 } groups acting as linkers (link) [3]. The
cluster type {Mo 132 } also has an interesting stoichiometric aspect in the sense that
it can be formally written as {Mo 132 } 1 {Mo 11 } 12 1 {(Mo)Mo 5 Mo 5
0 } 12 [5] (see below). The number twelve, an emblem of icosahedral symmetry, is significant in the
context of two Platonic solids: the icosahedron and dodecahedron, the latter having
12 faces, the former 12 vertices. Interestingly, the aforementioned {Mo 11 } unit, like
its smaller counterpart {(Mo)Mo 5 }, also shows a five-fold symmetry axis which is
necessary for the construction of spherical entities with icosahedral symmetry, be it
a {Mo 132 } type nanosphere or a spherical virus. The presence of the related 14 and
16 {Mo 11 } groups in wheel-shaped {Mo 154 } (1 {Mo 11 } 14 ) and {Mo 176 } (1 {Mo 11 } 16 )
type clusters (Table 14.1), respectively, also reveals the central role of the pentagonal building blocks. The two different types of {Mo 11 } building blocks can be distinguished easily as a lower symmetry (that is, C s ) is observed in the wheel-shaped
clusters resulting from the displacement of one of the {MoO 6 } octahedra (see Figures 14.3 and 14.4).
The structure of the {Mo 368 } type cluster [4], the largest inorganic species known
to date and also obtained from a special type of molybdenum blue solution, presents us with a paradigm shift with respect to symmetry breaking and changing
curvatures in the nanocosmos. The phenomenon of symmetry breaking is visible
at the surface due to the abundance of different large local symmetry areas as well
as the presence of negative curvatures in between positive curvatures (see Figures
14.5 and 14.6). The structure of this cluster can be considered as a hybrid between
the wheel- and ball-type clusters. The hybrid character is, in the terminology of ref.
[5], manifested by the occurrence of 24 C 5 -type {Mo 11 } groups of the ball-type
clusters together with the related 16 C s -type {Mo 10 } groups of the wheel-type clusters
which correspond to the abundant {Mo 11 } groups with only one MoO 6 octahedron
less (see [4]).
14 Oxomolybdates: From Structures to Functions in a New Era of Nanochemistry
454
Table 14.1, show the following characteristics:
. All listed clusters contain the fundamental pentagonal {(Mo)Mo 5 } building
block, comprising a central pentagonal bipyramidal {MoO 7 } group with six surrounding edge-sharing {MoO 6 } octahedra. These can occur in very different
environments.
. The units are, for example, central to the construction of spherically shaped
entities with positive curvatures. (Note that even the famous so-called bucky-ball
{C 60 } fullerene molecule contains 12 pentagonal ‘units’.) However, for the generation of more complex patterns, including negative as well as positive curvatures, that is showing symmetry breaking, a rather large number of negative and
positive vertices with polygons of different kinds, for example including heptagons, is necessary [4].
The highly symmetric [(pent) 12 (link) 30 ] type spherical clusters, such as the {Mo 132 }
type nanospheres (Figure 14.2, right), are comprised of 12 pentagonal {(Mo)Mo 5 }
groups (pent) connected by 30 {Mo 2 } groups acting as linkers (link) [3]. The
cluster type {Mo 132 } also has an interesting stoichiometric aspect in the sense that
it can be formally written as {Mo 132 } 1 {Mo 11 } 12 1 {(Mo)Mo 5 Mo 5
0 } 12 [5] (see below). The number twelve, an emblem of icosahedral symmetry, is significant in the
context of two Platonic solids: the icosahedron and dodecahedron, the latter having
12 faces, the former 12 vertices. Interestingly, the aforementioned {Mo 11 } unit, like
its smaller counterpart {(Mo)Mo 5 }, also shows a five-fold symmetry axis which is
necessary for the construction of spherical entities with icosahedral symmetry, be it
a {Mo 132 } type nanosphere or a spherical virus. The presence of the related 14 and
16 {Mo 11 } groups in wheel-shaped {Mo 154 } (1 {Mo 11 } 14 ) and {Mo 176 } (1 {Mo 11 } 16 )
type clusters (Table 14.1), respectively, also reveals the central role of the pentagonal building blocks. The two different types of {Mo 11 } building blocks can be distinguished easily as a lower symmetry (that is, C s ) is observed in the wheel-shaped
clusters resulting from the displacement of one of the {MoO 6 } octahedra (see Figures 14.3 and 14.4).
The structure of the {Mo 368 } type cluster [4], the largest inorganic species known
to date and also obtained from a special type of molybdenum blue solution, presents us with a paradigm shift with respect to symmetry breaking and changing
curvatures in the nanocosmos. The phenomenon of symmetry breaking is visible
at the surface due to the abundance of different large local symmetry areas as well
as the presence of negative curvatures in between positive curvatures (see Figures
14.5 and 14.6). The structure of this cluster can be considered as a hybrid between
the wheel- and ball-type clusters. The hybrid character is, in the terminology of ref.
[5], manifested by the occurrence of 24 C 5 -type {Mo 11 } groups of the ball-type
clusters together with the related 16 C s -type {Mo 10 } groups of the wheel-type clusters
which correspond to the abundant {Mo 11 } groups with only one MoO 6 octahedron
less (see [4]).
14 Oxomolybdates: From Structures to Functions in a New Era of Nanochemistry
454