New multidentate ligands for supramolecular coordination chemistry: double and triple helical complexes of ligands containing pyridyl and thiazolyl donor units

Abstract

Four new multidentate N-donor ligands L 1 -L 4 have been prepared which contain a combination of pyridyl and thiazolyl donor units. The syntheses of these ligands are facile and high-yielding, being based on reaction of an α-bromoacetyl unit with a thioamide to form the thiazolyl ring. The extended linear sequence of ortho-linked N-donor heterocycles (four for L 1 , six for L 2 ; five for L 3 ; and six for L 4 ) is reminiscent of the well-known linear oligopyridines, although these new ligands are much easier to make and have significantly different geometric coordination properties because the presence of the five-membered thiazolyl rings results in natural breaks of the ligand backbone into distinct bidentate or terdentate domains. Thus, the tetradentate ligand L 1 partitions into two bidentate domains to give dinuclear triple helicates [M 2 (L 1 ) 3 ] 4+ with six-coordinate first-row transition metal dications (M = Co, Cu, Zn). The hexadentate ligand L 2 partitions into two terdentate domains to give dinuclear double helicates [M 2 (L 2 ) 2 ] 4+ with six-coordinate metal ions (M = Cu, Zn). In the double helicate [Cu 2 (L 3 ) 2 ] 4+ the pentadentate ligand L 3 only uses its two terminal bidentate binding sites, resulting in four-coordinate Cu() centres and a non-coordinated pyridyl residue in the centre of each of the two ligand strands. These pendant pyridyl residues are directed towards each other to give a potentially two-coordinate cavity between the metal ions in the centre of the helicate. Similarly, in the double helicate [Cu 2 (L 4 ) 2 ] 4+ the metal ions are only four-coordinate, with each ligand having its central bipyridyl unit un-coordinated. This results in a potentially four-coordinate cavity between the two metal ions in the centre of the helicate. These easy-to-prepare ligands offer a great deal of scope for the development of multinuclear helicates.

Self‐assembly of anion‐binding supramolecular cage complexes

“…These ligands are all tetradentate, and accordingly, reaction with metal cations that prefer an octahedral coordination geometry requires 1.5 ligands per metal ion to provide the necessary six donor atoms (assuming that noncoordinating anions are used). The simplest stoichiometry that can occur is therefore M 2 L 3 , as commonly found in dinuclear triple helicates based on octahedral metal ions and bis-bidentate bridging ligands [19,20]. (Fig.…”

Totalsynthese von Nosiheptid

“…Imidazolen, [271] 1,2,4-Triazolen, [272] Tetrazolen [273] oder Thiazolen, [274] genutzt werden. [275] Die …”

Hydrothermal synthesis and crystal structure of a metal–organic coordination polymer with double-helical structure: [Fe(phen)(ipt)]n (ipt=isophthalate, phen=1,10-phenanthroline)

“…Each Fe(II) center displays a distorted octahedral coordination geometry, being coordinated by two nitrogen atoms of one phen ligand and four oxygen atoms from three different carboxylate groups of three ipt ligands. The average Fe-N bond length is 2.1891 (19) A A, and the Fe-O bond lengths vary from 2.0469(15) to 2.3182 (14) A A. The ipt ligand exhibits an interesting connection mode with metal ions.…”

“…This is because the nonlinear flexible or V-shaped dicarboxylate ligands can produce the helicity or flexuosity of the polymeric chains and aromatic bidentate chelate ligands can prevent the forming of high dimensional expanded structure [16,17] and provide potential supramolecular recognition for intermolecular p-p stacking interaction [18,19]. Based on the above synthesis strategy, we choose V-shaped dicarboxylate ligand ipt, bidentate chelate ligand phen and metal ion with appropriate geometry as the study system to explore potential charming helical structures.…”