Silver helicate

Fig. 1. List of organic ligands in copper and silver helical complexes.

Fig. 2. 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).

Figure 18.1 Typical tangle (T) and plaque (P) as visualised by silver impregnation in the cerebral cortex of a case of Alzheimer s disease. The extracellular plaque (10-50 pm diameter) consists of a central core of amyloid surrounded by glial processes and a number of neurites in a ring formation. The intracellular cytoplasmic tangle is composed of helical filaments in a paired format. (Reproduced with permission of Academic Press from Wischik and Crowther 1986)...

Figure 6 Ligands which form silver(I) complexes with helical structures.

A dinuclear silver(i) carbene complex, 22, was also isolated using a pyridyl-bridged biscarbene ligand (Scheme 7).65a,65b Complex 22 possessed a double helical structure with Ag-C bond distances of 2.080(4) and 2.087(4) A and a C-Ag-C angle of 165.5(2)°.65a Weak Ag-Ag interaction could also be observed with an Ag-Ag distance of 3.158 A.65a... 

The glass helices may be purchased from the Scientific Glass Apparatus Company, Bloomfield, N. J., or the American Instrument Company, Silver Spring, Md. Wire helices are readily made from No. 18 B. and S. gauge copper or Nichrome wire, by simultaneously winding two strands side by side on a j-in. steel mandrel. The spirals are cut into single helices by means of a thin emery wheel and then removed from the mandrel. 

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