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

Abstract

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.

Rational Design of a Coordination Cage with a Trigonal‐Bipyramidal Shape Constructed from 33 Building Units

“…[11] These units then react with each other with loss of H 2 bar; this type of reaction has been confirmed under ESI conditions, again with M = Cu 2+ (see Figure 5 b). [11] Linkage of three and four of these units with accompanying loss of H 2 bar leads to the open trigonal pyramid and the coordination cage 2, respectively (see Figure 5 c). The subsequent introduction of two more triangular units would then lead to the formation of the trigonal bipyramid 1.…”

“…[5] The replacement of these hydrogen atoms with bulkier Br atoms should prevent the formation of the octahedral cage. Therefore, we allowed tris(5-bromo-2-hydroxybenzyl)triaminoguanidinium chloride, [H 6 Br 3 L]Cl, [11] to react with PdCl 2 and NaHbar under similar conditions. Dark red plates of (Et 3 NH) 6 -(Et 4 N) 6 [{Pd 3 (Br 3 L)} 6 (m-bar) 9 ] (1) formed; the result of the X-ray structure analysis is shown in Figure 3.…”

Derivatives of the triaminoguanidinium ion, 6. Aminal-forming reactions with aldehydes and ketones

“…1) are readily accessible, simple building blocks for organic synthesis, which due to their C 3 -symmetric topology and functional group presence offer diverse opportunities for the preparation of other ionic or neutral guanidine derivatives and of nitrogen heterocycles [1,2]. By reaction with aldehydes or ketones, the three NH 2 groups in 1 allow the straightforward conversion into tris(imines) (or (tris(hydrazones)) 2 [2][3][4][5][6], some of which were employed as ligands with multiple coordination sites in transition metal complexes showing remarkable three-dimensional architectures [2,5,7,8].…”

Derivatives of the Triaminoguanidinium Ion, 2. Prototropic Tautomerism, Crystal and Molecular Structure of N,N´,N´´-Tris(propan- 2-iminyl)guanidine [1, 2]

“…Deprotonated forms of tris(2-hydroxybenzylidenamino)guanidinium [6 -9] and tris[α-(hydroxyimino)alkylidenamino]guanidinium salts [10] have recently been identified as triangular ligands for transition-metal complexes with novel architectures. The solid-state structures of a few tris(2-hydroxybenzylidenamino)guanidinium salts [6,7] have been determined; they show a planar C(NNC) 3 core with phenyl rings moderately tilted against this plane. To our knowledge, no crystal structures have been reported for neutral triaminoguanidine-derived trishydrazones.…”