One-pot synthesis and X-ray studies on cyclic oligobipyridines and one of their dinuclear ruthenium complexes

Abstract

A one-pot synthesis of three new macrocycles containing two, three or four 2,2'-bipyridine units is described; the X-ray analysis of the bis-bipyridine ligand reveals a cyclophane type structure; the X-ray structure of one of the diastereoisomers of the dinuclear ruthenium complex is also described and shows two metal centres held in close proximity.

Efficient Stereospecific Syntheses of Chiral Ruthenium Dimers

“…The other two dinuclear complexes, Λ,Λ- 4 and Λ,Δ- 4 , were obtained similarly by condensing appropriate dione and diamine species. 1 H and 13 C NMR spectra of the diastereomers Δ, Δ- 4 and Δ,Λ- 4 are indistinguishable, probably because the large distance between Ru centers (∼12.7 Å);2a however, circular dichroism (CD) data clearly identify the diastereomers and enantiomers. The Δ,Λ- 4 meso diastereomer is not optically active 17 whereas the enantiomers, Δ,Δ- 4 and Λ,Λ- 4 , show equal but opposite molar ellipticities (shown in Figure ), as expected.…”

“…Relatively little attention, however, has been paid to the absolute stereochemistry of these supermolecules in cases where substitutionally inert, octahedral tris chelate [Ru(L-L) 3 ] z + complexes are used as molecular building blocks. Supramolecular species, such as dimers, trimers, dendrimers, and polymers, constructed from these tris(bidentate) complexes are usually assembled via ligand displacement reactions with little direct control for the product stereochemistry. As a consequence of the chirality of these building blocks (Δ or Λ), the products consist of complicated mixtures of enantiomers and diastereomers which are difficult, if not impossible, to further purify .…”

“…Formation of the phenazine ring has been optimized and occurs in nearly quantitative yield, which is essential for the practical synthesis of higher nuclearity species. Previously, various phenazine compounds formed via this type of condensation reaction were obtained in yields ranging from 30 to 94%, most commonly around 80%. 2ab,,11ab, While all of these reactions were performed in nonaqueous solvents, we have found that aqueous or mixed aqueous solvents at reflux give isolated yields of 95−98% for the synthesis of 4 . The resulting aromatic bridge is symmetrical and rigid, is formed irreversibly, and provides an electronic conduit between redox centers.…”

Supramolecular Isomerism in Coordination Compounds: Nanoscale Molecular Hexagons and Chains

“…The hexagon represents a discrete planar species of which only a few examples have been reported. , The zigzag polymer has been widely encountered, whereas the helix remains quite rare in the context of coordination polymers. , A suitable molecular component that might serve as a building block in this context is 1,3-benzenedicarboxylic acid, H 2 bdc, 5-substituted forms of which can self-assemble into molecular hexagons 8a,19,23 or bdc, which can serve as a bifunctional ligand . In this contribution, we report the synthesis and structural characterization of a nanoscale, neutral, planar hexagon, 1 , and its supramolecular isomeric zigzag chain, 2 , each resulting from modular self-assembly of 5-NO 2 -bdc and Cu(II) (Figure ) .…”

Dinuclear ruthenium(II) bipyridine complexes having non-symmetric α,α′-diimine based neutral bridging ligands.

“…Introduction ligands to bring together different ruthenium-bipyridine fragments in the polynuclear array. Although mononuclear Since the discovery of the important photo-redox activi-systems are extensively studied, current interest is now II 21 ty of [Ru (bpy) ] (bpy52,29-bipyridine) complexes, primarily focused on the supramolecular assemblies of 3 there has been continuous research activity in the direction molecular components having well-defined structures and of developing new and effective redox catalysts and properties [15][16][17][18][19][20][21][22][23][24][25][26][27][28]. Photo-induced energy and electron photosensitizing devices involving the ruthenium-transfer processes in supramolecular systems can be exbipyridine moiety [1][2][3][4][5][6][7][8][9][10][11][12][13][14].…”