A New Ligand for the Formation of Triangular Building Blocks in Supramolecular Chemistry

In this article we describe the synthesis, characterisation and metal binding properties of tris(5‐bromo‐2‐hydroxybenzylidene)triaminoguanidinium chloride [H 6 Br 3 L]Cl ( 1 ), which can be seen as a triangular building block for supramolecular chemistry. 1 crystallises either in a triclinic ( 1a ) or a rhombohedral ( 1b ) system depending on the used solvent . The pure ligand adopts a conformation unfavourable for the coordination of metal centres, but in the presence of a base or a basic metal salt, a change in the conformation can be observed. The reaction of 1 with (NH 4 ) 6 [Mo 7 O 24 ] in the absence of further base results in the formation of small, red crystal needles with the formula [Mo(O) 2 (OH 2 )(H 3 Br 3 L)]·2 DMF ( 2 ), while the reaction of 1 with CuCl 2 , sodium 5,5‐diethylbarbiturate (NaH bar ) and Et 3 N leads to the formation of dark red‐black crystals with the formula (Et 4 N) 2 [{Cu(H bar )} 3 Br 3 L] ( 3 ). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)