Oligopyridine ligands

Of particular importance are oligopyridine ligands such as 2,2 6, 2",2" 6", 2""-pentapyridine. These molecules allow synthesis of helical, inter-finked and knotted molecular arrays.1 7 Similar species with interlocking rings are the catenands and torands.m Some examples of oligopyridines are (9-XVIII) and (9-XIX). Other nitrogen heterocycles are the following ... 

Baca, S.G, Adams, H., Sykes, D., et al. (2007) Three-component coordination networks based on [Ru(phen)(CN)4] anions, near-infrared luminescent lanthanide(lll) cations, and ancillary oligopyridine ligands structures and photophysical properties. Dalton Transactions, 2419. 

Using the longer oligopyridine ligand 2,2 6, 2" 6",2" 6", 2""-sexipyridine (spy) (4), Constable et al. have shown that some metal ions can induce the formation of double-helical aggregates. In particular, (4) was allowed to complex with six different metal ions and the resultant structure of each aggregate was determined [16]. 

Armspach D, Constable E C, Diederich F, Housecraft C E and Nierengarten J-F 1996 Bucky-ligands fullerene-substituted oligopyridines for metallosupramolecular chemistry J. Chem. Soc., Chem. Commun. 2009-10... 

Oligopyridine two-dimensional ligands connected by alkyne spacers with 1-4 ethynyl groups as photoactive conductors of molecular size 96CC1707. 

SCHEME 36. Divalent /J-D-galactopyranosides built on oligopyridine metal ligand scaffolds.275... 

S. Orlandi, R. Annunziata, M. Benaglia, F. Cozzi, and L. Manzoni, Synthesis of some oligopyridine-galactose conjugates and their metal complexes A simple entry to multivalent sugar ligands, Tetrahedron, 61 (2005) 10048-10060. 

Bicyclo(4.4.1 Jundecapentaene complexes with group VI B metals, 12 237 Bidentate ligands, reactions with tetracyano complexes containing oxo or nitrido ligands, 40 310-313 Bidentate oligopyridines, 30 72-73 Bidentate polysulfide complexes, bond lengths, 31 114... 

Bridging ligands, 32 56 Fe—S clusters, 38 172 Bridging oligopyridines, 30 72-73 Bridging tetrazadiene, in transition metal complexes, 30 43, 48, 49... 

Suitably substituted diazines also form chelate complexes, e.g. 2,3,5,6-tetrakis(a-pyridyl)pyrazine yields red tridentate complexes with Fe11. In the fast development of metallosupramolecular chemistry, many other polydentate ligands, based on 2,2 -bipyridyl units, have been obtained and studied (94CI(L)56). Thus, two molecules of oligopyridine (58) interact with various metal ions (Fe2+, Co2+, Cu2+ etc.) to form a double-helical [M2L2]4+ complex in which each metal is bonded to a tridentate region from each ligand. 

Exodentate multitopic ligands are used to link transition metal ions into building blocks. Some examples of such ligands are 2,4,6-tris(4-pyridyl)-l,3,5-triazine, oligopyridines, and 3- and 4-pyridyl-substituted porphyrins. 

The strain introduced into the ligand will be even higher in complexes of the higher oligopyridines, and it was at one time suggested that they could not exhibit their maximum denticity in monodentate complexes. It is now clear that quaterpyridine may act as a quaterdentate ligand, albeit with very unsymmetrical M—N distances. 

Terpyridine is the simplest oligopyridine capable of forming a double-stranded helicate, but early attempts to interact this ligand with copper(I) led to air-unstable products that readily oxidised to the well known octahedral bis(terpyridine)cop-... 

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