Self-assembled Transition Metal Coordination Frameworks of ...

pp g _g _4_,_ C0pper(II) complexes
refluxed for 1 h and allowed to stand at room temperature. Dull brown colored mass
separated out was filtered, washed with methanol and ether and dried over P4010 in
vacuo. Yield: 0.260 g (56.0%). Elemental Anal. Found (Calc.): C, 40.90 (40.76); H,
3.23 (2.77); N, 13.37 (l3.58)%. Molar conductivity (AM, l0'3 M DMF): 28 Q" cmz
mol".
[Cu;(HL6)Br;]Br (19)
A solution of CuBr2 (0.271 g, 1.2 mmol) in 10 ml of methanol was added to a
solution of H2L° (0.291 g, 0.6 mmol) in 70 ml boiling methanol and refluxed for ‘/2 h
and allowed to stand at room temperature. Yellow brown colored solid separated out
was filtered, washed with methanol and ether and dried over P4010 in vacuo. Yield:
0.269 g (48.9%). Elemental Anal. Found (Calc.): C, 34.94 (34.35); H, 2.24 (2.06); N,
11.60 (11.45)%. Molar conductivity (AM, 10-3 M DMF): 63 Q" cmz mol".
4.3. Results and discussion
All the copper complexes, except 8, were synthesized by the reaction between
1:2 ratios of corresponding ligand to metal salts under neutral conditions. All the
complexes, except 8, 9 and 13, are found to be bimetallic within the coordination
pockets of respective ligands. For all complexes the respective ligands coordinate
either by monodeprotonated or by dideprotonated forms. The solvents used were
methanol, ethanol or methanol chloroform mixture mainly with a view to dinuclear
complexes [17]. So far and in the present study, the Cu(Il) species are found reluctant
to fomi molecular squares with carbohydrazones and thiocarbohydrazones. According
to the thermodynamic analysis of self-assembly macrocyclization, desired
macrocyclic products exist as major species only within a limited range of
concentration under certain reaction conditions. ln order to accomplish self-assembly
already at low concentration, the coordinative bonds should exhibit considerable
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