Self-assembled Transition Metal Coordination Frameworks of ...

q H _ Manganesefll) complexes
[Mn2(H;L6)HL6]2(ClO4)6~ 31120 (23)
Mn(ClO4)2- 6H2O (0.256 g, 0.70 mmol) in 10 ml of methanol was added to a
boiling solution of HZL6 (0.169 g, 0.35 mmol) in 20 ml methanol with a drop of
HCIO4 and refluxed for 1 h and allowed to stand at room temperature. The yellow
powder precipitated was filtered, washed with methanol and ether and dried in vacuo
over P40“). Yield: 0.180 g (88%). Elemental Anal. Found (Calc.): C, 43.36 (43.08); H,
3.14 (2.93); N, 14.43 (14.35)%.
5.3. Results and discussion
The carbohydrazones and thiocarbohydrazones having well defined and
appropriately separated two coordination pockets, using the bridging mode of sulfur
or oxygen, in principle have a better chance of control over the outcome of a self­
assembly process to produce the predefined square grids of metals. The synthesis of
complex 19 was done in neutral medium, while the others were carried out in acidic
medium. The formation of these kind of materials are hard to prove with common
physico-chemical techniques as the formation of multinuclear manganese complexes
of thiocarbohydrazones and carbohydrazones are not reported previously, and
especially when the Mn(II) complexes lacks stability compared with those of other
divalent 3d metals. Unfortunately, all attempts to crystallize any of the complexes
went in vain. The MALDI MS spectra revealed sensible fragmentation peaks of the
fonnation of tetranuclear structures for all complexes except 20, which was assigned
to be a dinuclear complex. This can be attributed to the fonnation of
thermodynamically controlled single product and the square grids 19, 21, 22 and 23
have a sufficient thermodynamic advantage over the other possible species under the
reaction conditions. The complexes 21, 22 and 23 were formed in the 1:1 ratios even
though we used a 1:2 ratios of respective ligand to metal salt for syntheses. The
structure and stability of coordination complexes under ionization conditions are
dependent on various factors like the ligand itself, metal ions, counter ions, solvent,
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