TY - JOUR
T1 - Ferrocene encapsulated within symmetric dendrimers
T2 - A deeper understanding of dendritic effects on redox potential
AU - Stone, Diane L.
AU - Smith, David K.
AU - McGrail, P. Terry
PY - 2002/2/6
Y1 - 2002/2/6
N2 - Ferrocene has been encapsulated within a symmetric ether-amide dendritic shell and its redox potential monitored in a variety of solvents. The dendritic effect generated by the branched shell is different in different solvents. In less polar, non hydrogen bond donor solvents, attachment of the branched shell to ferrocene increases its E1/2, indicating that oxidation to ferrocenium (charge buildup) becomes thermodynamically hindered by the dendrimer, a result explained by the dendrimer providing a less polar medium than that of the surrounding electrolyte solution. The effect of electrolyte concentration on redox potential was also investigated, and it was shown that the concentration of "innocent" electrolyte has a significant effect on the redox potential by increasing the overall polarity of the surrounding medium. Dendritic destabilization of charge buildup is in agreement with the majority of reported dendritic effects. A notable exception to this is provided by the asymmetric ferrocene dendrimers previously reported by Kaifer and co-workers, in which the branching facilitated oxidation, and it is proposed that in this case the dendritic effect is generated by a different mechanism. Interestingly, in methanol, the new symmetric ferrocene dendrimer exhibited almost no dendritic effect, a result explained by the ability of methanol to interact extensively with the branched shell, generating a more open superstructure. By comparison of all the new data with other reports, this study provides a key insight into the structure-activity relationships which control redox processes in dendrimers and also an insight into the electrochemical process itself.
AB - Ferrocene has been encapsulated within a symmetric ether-amide dendritic shell and its redox potential monitored in a variety of solvents. The dendritic effect generated by the branched shell is different in different solvents. In less polar, non hydrogen bond donor solvents, attachment of the branched shell to ferrocene increases its E1/2, indicating that oxidation to ferrocenium (charge buildup) becomes thermodynamically hindered by the dendrimer, a result explained by the dendrimer providing a less polar medium than that of the surrounding electrolyte solution. The effect of electrolyte concentration on redox potential was also investigated, and it was shown that the concentration of "innocent" electrolyte has a significant effect on the redox potential by increasing the overall polarity of the surrounding medium. Dendritic destabilization of charge buildup is in agreement with the majority of reported dendritic effects. A notable exception to this is provided by the asymmetric ferrocene dendrimers previously reported by Kaifer and co-workers, in which the branching facilitated oxidation, and it is proposed that in this case the dendritic effect is generated by a different mechanism. Interestingly, in methanol, the new symmetric ferrocene dendrimer exhibited almost no dendritic effect, a result explained by the ability of methanol to interact extensively with the branched shell, generating a more open superstructure. By comparison of all the new data with other reports, this study provides a key insight into the structure-activity relationships which control redox processes in dendrimers and also an insight into the electrochemical process itself.
UR - http://www.scopus.com/inward/record.url?scp=0037028551&partnerID=8YFLogxK
U2 - 10.1021/ja0117478
DO - 10.1021/ja0117478
M3 - Article
C2 - 11817961
AN - SCOPUS:0037028551
SN - 0002-7863
VL - 124
SP - 856
EP - 864
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 5
ER -