Until now it has been a tremendous and ongoing challenge to initiate a variety of chemical reactions at well-defined positions even of the same and structurally well-defined nanoobject, especially if significant property changes or novel functionalities are intended. [1] This aim has now been achieved for giant ring-shaped molybdenum oxide based clusters of the type {Mo 154 } and {Mo 176 } which can be obtained in related crystalline salts in a facile high-yield synthesis and exhibit nanosized cavities, a variety of sites with different well-defined functional groups, and overall are comparable to a nanostructured landscape. [2,3] Here we report the incorporation of paramagnetic metal centers, that is, Cu 2 ions, in cavities of these ringsÐwhich are spanned by four O atoms and have the corresponding appropriate sizeÐaccording to a basic type of self-assembly process leading to nanoobjects all of which have the ring topology. Important in this context is that this allows a variety of deliberate concomitant modifications under alterable boundary conditionsÐsuch as the pH, temperature, and/or presence of different substratesÐcorresponding to the different sites. [4] The procedure opens perspectives not only for a new type of nanochemistry but also for an understanding of a basic reaction type of material organization (see below).
The reduction of an acidified aqueous polymolybdate solution with copper powder leads to the crystalline black compound 1, which was characterized by elemental analyses (NH 4 ) 26 [(H 4 Cu II 5 Mo V 28 Mo VI 114 O 432 (H 2 O) 58 ] ´% 300 H 2 O 1
(including cerimetric titration to determine the formal number of Mo V centers), thermogravimetry (to determine the amount of crystal water), spectroscopy (UV/Vis/NIR, infrared (IR), resonance-Raman, ESR), single-crystal X-ray structure analysis, [5] and bond valence sum (BVS) [6] calculations (to determine the positions of the H 2 O molecules and to