Helical Frameworks

Copper(I)and Silver(I) Complexes with Helical Frameworks 

The number of one-dimensional infinite single-helical copper(I) and silver(I) complexes is rather limited. They are characterized by a single strand of ligands twisting around the helical axis defined by metal ions [Fig. 2(a)]. It may be left-handed or right-handed. When ligand Li reacted with two equivalents of [Cu MeCN)4]BF., in a mixture of 

Schematic views of copper and silver helical arrangements (a) infinite single strand (b) 3-D single helical copper(I) complex with mixed ligands (c) dinuclear double helicate (d) trinuclear double helicate (e) infinite double helicate (f) infinite chiral double helicate of copper(II) with arginine and m-phthalate (g) triple helicate of silver(I). 

Tetrahedral coordination of the metal ion is not an essential requirement for formation of this t3qje of helical structure. Two-coordinate silver(I) ion plays an important role in the formation of a helical framework, that is, the stereoconformation of the ligand itself is maintained on coordination to Ag(I) and arranged in a onedimensional helical chain. Reaction of the bidentate optically active ligands (4R,5R)- and (4S,5S)-4,5-bis(2-(2-p3rridyl)ethyl)-l,3-dioxolane (Rfi-La or SjiS-Ls) with silver(I) trifluoromethanesulfonate in metha- 

Double helicates constitute the most abundant species among the copperd) and silverlD helical complexes. In the presence of the tetrahedral Cud) and Agd) ions, two oligopyridines can wrap around each 

CoPPER(I) AND SlLVER(I) COMPLEXES WITH HELICAL FRAMEWORKS 

Copper(I) and silver(I) complexes derived from odd-numbered oligo-pyridines present a different situation. Quinquepyridine (LlB) in dinuclear helicates usually involves a rotation about an interannual 

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X-Ray analyses of bridged [7]thiaheterohelicenes 59a-c and 60 indicate that the dihedral angles between terminal thiophene rings of the helical framework vary significantly from 22° for helicene 60 to 59° for helicene 59c. This represents as increase of 37° or 168% <2002JOC1795>. 

In some reactions, there may be more than one possible reaction site. Typical Mitsunobu reaction partners in such reactions include pyridones, sulfahydantoins, etc. A few examples are shown below. Quinoline 254 was prepared from the corresponding pyridone in good yield reduction of the nitro group to the aniline was followed by condensation with another quinoline derivative to prepare quinoline based oligomers that form helical frameworks. ... 

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