Hexadentate chiral ligand

Ward and coworkers reported the synthesis of a chiral C3-symmetric hexadentate tripodal ligand tris[3- 2-(pinene[4,5]pyridyl) pyrazolyl]-... 

Keene and coworkers made the chiral trinuclear ruthenium complex [(Ru(Phen)3(62)] (5.102) by treatment of the hexadentate bridging ligand HAT (62) (HAT = 1,4,5,8,9,12-Hexaazatriphenylene) with three equivalents of the A-/A-[Ru(Phen)2(CO)2] building block (Figure 5.44). Keene and coworkers investigated this approach thoroughly and... 

An order of effectiveness has been established and a mechanism proposed for the removal of iron from ferritin by several 3-hydroxy-4-pyridinone chelators. The removal of iron from ferritin is, as one would expect, considerably slower than from calcein or doxorubicin (cf. above) or from transferrin. Rate constants are between 1.5 x 10 s and 7.5 x 10 s for removal of iron from ferritin by a series of hexadentate ligands each consisting of three substituted A-hydroxypyrimidinone or A-hydroxypyrazinone units, the rate decreasing with increasing substituent bulk. The slowest rate approximates to that for removal of iron from ferritin by desferrioxamine. The influence of chirality on the kinetic barrier provides insight into the detailed mechanism of removal in these systems.Slow removal of iron from ferritin by chelators should be contrasted with rapid reductive removal. ... 

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