Conformational Change of Ligand Chain

It is thus expected that the conformation of the polymer-ligand chain will influence the reactivity of a metal complex. The influence of the conformational change of a poly(N-vinyl-2-methylimidazole)(PVMI 3) ligand has been studied in the electron-transfer reaction of a Co(III) complex in aqueous-alcoholic solvents87.  

3 O rate constant for reaction between [Co(III)(en)2(PNVl)CllCl2 and Fe(ll)edta, A rate constant for reaction between monomeric [Co(IIlXen)2(NEI)CllCli and Fe(II)edta, intrinsic viscosity of PVMI-Co complex solution, PVNI = poly(N-vinyl-2-methylimidazole), 

The higher reactivity of the PVMI-Co(III) complex is attributed to the electrostatic domain of the polymer complex, as in the above PVP system. When the PVMI chain contracts, the charge density in the polymer domain increases and the reaction rate also increases. On the other hand, when the polymer chain expands, the electrostatic domain is weakened, which produces a fall in reactivity. These results confirm that the conformation of the polymer complex is closely related to the strength of its electrostatic domain and to the reaction rate. The effects of the polymer chain on reactivity are to be understood not only in terms of static chemical environment but also as dynamic effects which vary with the solution conditions, e.g. pH, ionic strength, solvent composition, temperature, and so on. 

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