Trefoil Knots as Transition Metal Ligands - Specific Kinetic, Electrochemical, and Photochemical Properties

4 Trefoil Knots as Transition Metal Ligands -Specific Kinetic, Electrochemical, and Photochemical Properties 

Although the preparative yields for most of the dicopper(I) trefoil knots described above were modest (0.5 to 8% for the methylene-bridged knots, 30% for the phe-nylene-bridged knot Cu2(K-84)p+) the amounts obtained were sufficient to undertake the study of their specific properties. 

The extensive kinetic studies of their cyanide-assisted demetalation (determination of rates and mechanisms [110]) as well as the study of their electrochemical and photophysical properties [97] enabled us to gain insight into the particular properties of knotted structures which appeared to be strongly determined by both topological and structural (i.e. geometrical) effects. 

If the properties of the various dinuclear complexes investigated appear to be very sensitive to both factors, we can nevertheless discriminate them roughly (and in a somewhat artificial way) by discussing the data obtained for the family of methylene-bridged knots and related unknotted complexes and, separately, those obtained for the phenylene-bridged knots. 

The demetalation process was followed by absorption spectrophotometry (measurement of the decay, as a function of time and cyanide concentration, of the di-copper(I) complexes characteristic metal-to-ligand-charge-transfer (MLCT) bands in the visible region [111]) which gave access to the kinetic parameters, in particular to the second-order dissociation rate constants CN given in Table 1. 

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