S. Gould et al., SIZE-SELECTIVE DIFFUSION OF FERROCENES THROUGH MOLECULAR VOIDS CREATED BY PHOTOLYSIS OF COPOLYMERIC FILMS, Journal of physical chemistry, 99(43), 1995, pp. 16052-16058
Photolysis of the copolymeric films poly(x)[Ru(Me(1)bpy)(2)(vpy)(2)](P
F6)(2x), (1 - X)[Ru(vbpy)(3)](PF6)(2-2x) formed by reductive electropo
lymerization on Pt electrodes (surface coverage Gamma = 2 x 10(-9) to
6 x 10(-9) mol/cm(2)) results in loss of the fragment -[-Ru(Me(4)bpy)(
2)](PF6)(2). For x = 0.4-0.6 electrochemical and angle-resolved XPS me
asurements before and after photolysis show that film thickness is una
ffected by photolysis. Diffusion of ferrocene and substituted ferrocen
es through the films was studied by rotated disk voltammetry, from whi
ch values for PDs,pol were derived. D-s,D-pol is the diffusion coeffic
ient of ferrocene through the film, and P is the partition coefficient
within the film. Removal of -[-Ru(Me(4)bpy)(2)](PF6)(2) by photolysis
creates molecular sized voids and increases PDs,pol by factors of 10-
20. The photolyzed films act as size-selective membranes with PDs,pol,
decreasing by as much as 16 as the volume of the ferrocene increases
from 150 to 500 Angstrom(3). The diffusional properties of the films c
an be varied somewhat by adding substituents to the bpy rings of the l
eaving group or by partly filling the molecular voids by coordination
to pyridyl groups released in the photolysis step.