3,3 -Bridged-2,2 -bipyridines

Bridged bipyridines and terpyridines, fused systems with several pyridine rings or with indole and pyridine fragments simultaneously, rigid pyridino-phanes 91T6851. 

Kanomata N, Suzuki J, Kubota H, Nishimura K, Enomoto T (2009) Synthesis of planar-chiral bridged bipyridines and terpyridines by metal-mediated coupling reactions of pyridinophanes. Tetrahedron Lett 50 2740-2743... 

The Lehn group synthesised the trinuclear copper(I) complex of the substituted 2,2 -bipyridyl/ether derivative 29 and confirmed its helical structure by X-ray diffraction (Figure 6.15). A dinuclear copper(I) complex of 30 (Figure 6.15) was also synthesised and subsequently the corresponding dimeric ethane-bridged bipyridine and phenanthroline ligands were also demonstrated to yield similar di-helicate copper(I) species. These results thus indicate that helicate formation is tolerant towards minor modification of ligand structure. ... 

Ihniguchi, L, Toyosawa, K., IVunaguchi, M., Yasukouchi, K., Voltammetric Response of Horse Heart Cytochrome C at a Gold Electrode in the Presence of Sulphur-Bridged Bipyridines , J. Elec-troanal. Chem. Interfac. Electrochem. 140 (1982) 187-193. 

With free acetylene, coupling at both termini is readily achieved as illustrated by the preparation of ethynyl-bridged bipyridine 235 (Scheme 88). . This is an example of a... 

Figure 8 Schanatic drawing of the ruthenium(II) complex with styryl-bridged bipyridine ligand.

In continuation of our research on design of novel catalysts for selective organic transformations, we have synthesized more flexible, expanded PNN-type pincer ruthenium complexes (18-20). However, only modest catalytic activity and selectivity was observed with these bridged-bipyridine-based PNN-Ru(II) complexes in amide hydrogenation (25-65% yields) and other reactions [70]. This is likely a result of cyclometalation of the active species 21 and 22, which is detrimental to the catalysis (Scheme 8 Fig. 10). The low stability of the expected dearomatized complex (20a) formed by deprotonation of 20 was also detrimental to catalysis. 

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