Self-assembled Transition Metal Coordination Frameworks of ...

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magnetism of polynuclear complexes containing magnetic metal ions, often called
molecular nano magnets, has captured the imagination of chemists and physicists
alike. Synthesis and structural characterization of novel materials are of special
interest in the chemical arena. One of the characteristic features of molecular
magnetism is its deeply interdisciplinary character, bringing together organic,
organometallic and inorganic synthetic chemists as well as theoreticians fi"om both the
chemistry and physics communities, and materials and life-science specialists [6].
Another important impetus for investigating polynuclear manganese clusters lies in
their biological relevance. It has become accepted that the water-oxidizing complex of
photosystem II contains a tetranuclear manganese aggregate [7,8]. The role of
manganese in biological systems is related to its ability to yield polynuclear
complexes where various oxidation levels, involving single atom oxidation states in
the range II-IV, are accessible [9]. In the design of nanoscale materials, grid structures
are of special interest because a two-dimensional, precise grid like configuration of
metal centers suggests applications in information storage and processing technology.
Moreover, depending on the packing such assemblages of grids have the potential to
exhibit either long-range order or single molecule magnetic behavior.
Manganese complexes of thiosemicarbazones are infrequently reported [10­
I6]. Ferromagnetic and antiferromagnetic cubane like Mn(H) complexes of di-2­
pyridyl ketone in the gem-diol form are reported [17]. Self-assembled [3x3] Mn(H)
grid complexes are reported to exhibit well defined electrochemical and magnetic
properties, and solution studies indicate that groups of metal ions within the grid can
be selectively oxidized from Mn(H) to Mn(lII) [18] and possible to isolate mixed
valence complexes, molecular devices. A self-assembled Mn(H) square grid
[Mn4L4](ClO4)8 where L is a bis-tridentate (two N, N, N pockets) ligand is reported as
having four octahedral coordination centers [19], this complex decomposes
completely in DMF. Compared to other transition metal molecular square grids there
are only few reports for Mn(II). There was no previous report of self-assembled
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