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groups so that no interactions can occur and the rod can be

easily shifted with respect to each other.

From structure to function

The compounds discussed in this report should illustrate that

sulfate anions and their derivatives are very suitable to construct

different structural architectures with unusual co-ordination types

or linkages. The question that arises from these investigations is

how special properties or functions can be addressed or tailored

by using these ligands. Some ideas should be mentioned:

a) Defining co-ordination geometries: The disulfate examples

[M(S

2

O

7

)

3

]

2-

and Pd(S

2

O

7

) show that S

2

O

7

2-

ions are capable

of stabilising unusual electronic configurations (high spin d

8

for

Pd

2+

) and co-ordinations (octahedral surrounding of Si

4+

);

b) Tailoring linkage: By choosing the appropriate reaction

conditions and by using the suitable anions as linkers, the

dimensionality of a given structure can be determined. Thus,

the distances of metal atoms with respect to each other are

adjustable, a key issue for influencing phenomena like co-

operative magnetism and luminescence; and

c) Precursors: The sulfates and sulfate derivatives are often

thermally quite labile compounds. Their decomposition

might be a suitable way for the preparation of new

compounds in different shapes (particle, layers etc.). It has

turned out that the typical decomposition products are

oxides, sulfides or even oxide-sulfides. In many cases, the

compounds obtained from the decomposition can hardly be

obtained using other methods, so the compounds under

investigation are useful precursors.

Outlook

Sulfates and their derivatives are only a small part of the large

group of oxoanions. Besides these tetrahedral species, other

anions are of interest, for example the trigonal planar carbonates

(CO

3

2-

) and nitrates (NO

3

-

) or pyramidal anions like SeO

3

2-

. In any

case, the first part of the investigations must be the development

of suitable preparative routes. In the case of carbonates and

nitrates this is difficult because the corresponding acids are

unstable (H

2

CO

3

) or only moderately stable (HNO

3

). Moreover,

nitrates and carbonates are thermally labile, so high temperature

methods cannot be applied. For nitrates we have already

conducted a number of experiments using fuming nitric acid or

even its anhydride, N

2

O

5

.We could successfully prepare a number

of anhydrous nitrates, especially of the noble metals. Several

selenites could also be prepared, mainly by solid state reactions

using SeO

2

as an initial compound but also by high temperature

techniques using selenic acid, H

2

SeO

4

. Carbonates, however, are

underexplored to a large extent. For example, up to now no

carbonate of a noble metal has been reported, and there is no

suitable route for their preparation in sight. Thus, a lot of work has

to be done for a full understanding of oxoanionic compounds.

Professor Mathias SWickleder

Inorganic Functional Materials

Institute of Inorganic andAnalytical Chemistry

Justus Liebig University, Gießen, Germany

tel :

+49 641 99 34100 / 34101

mathias.wickleder@anorg.chemie.uni-giessen.de www.uni-giessen.de/cms/fbz/fb08/Inst/iaac/wickleder www.horizon2020projects.com

H O R I Z O N 2 0 2 0 P R O J E C T S : P O R TA L

I S S U E S E V E N

61

P R O F I L E

C H E M I S T R Y

Fig. 9 Chain structure of Zr(CF

3

SO

3

)

4