New multidentate ligands for supramolecular coordination chemistry: doubleand triple helical complexes of ligands containing pyridyl and thiazolyl donor units
Cr. Rice et al., New multidentate ligands for supramolecular coordination chemistry: doubleand triple helical complexes of ligands containing pyridyl and thiazolyl donor units, J CHEM S DA, (5), 2001, pp. 550-559
Citations number
48
Categorie Soggetti
Inorganic & Nuclear Chemistry
Journal title
JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
Four new multidentate N-donor ligands L-1-L-4 have been prepared which cont
ain a combination of pyridyl and thiazolyl donor units. The syntheses of th
ese ligands are facile and high-yielding, being based on reaction of an alp
ha -bromoacetyl unit with a thioamide to form the thiazolyl ring. The exten
ded 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 l
inear oligopyridines, although these new ligands are much easier to make an
d have significantly different geometric coordination properties because th
e presence of the 5-membered thiazolyl rings results in natural breaks of t
he ligand backbone into distinct bidentate or terdentate domains. Thus, the
tetradentate ligand L-1 partitions into two bidentate domains to give dinu
clear triple helicates [M-2(L-1)(3)](4+) with six-coordinate first-row tran
sition metal dications (M=Co, Cu, Zn). The hexadentate ligand L-2 partition
s 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 bi
dentate binding sites, resulting in four-coordinate Cu(II) centres and a no
n-coordinated pyridyl residue in the centre of each of the two ligand stran
ds. 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 m
etal ions are only four-coordinate, with each ligand having its central bip
yridyl unit non-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 mult
inuclear helicates.