Electrochemistry of the inclusion complexes formed between the cucurbit[7]uril host and several cationic and neutral ferrocene derivatives.
We have investigated the formation of inclusion complexes between the host cucurbit[7]uril (CB7) and three cationic and four neutral ferrocene-containing guests: (ferrocenylmethyl)trimethylammonium (2(+)), butyl(ferrocenylmethyl)-dimethylammonium (3(+)), (ferrocenylmethyl)heptyldimethylammonium (4(+)), hydroxymethylferrocene (5), (((methoxy)-ethoxy)ethoxy)methylferrocene (6), 1,1'-di(hydroxymethyl)ferrocene (7), and 1,1'-di((((methoxy)ethoxy)ethoxy)methyl)ferrocene (8). The formation of highly stable inclusion complexes (K > 10(7) M(-1)) was verified in all cases using NMR spectroscopic techniques. From cyclic voltammetric experiments, we observed that CB7 complexation of the cationic guests (2(+)-4(+)) leads to significant anodic shifts on the ferrocene oxidation half-wave potentials, while the measured potential shifts were smaller in the case of the neutral guests (5-8). Encapsulation of all guests resulted in a substantial decrease of the standard rate constant for heterogeneous electron transfer. However, inclusion complexation of the neutral guests led to quasi-reversible voltammetric behavior, in which the anodic peak potential is more sensitive to scan rate than the corresponding cathodic peak potential, suggesting a minor degree of structural rearrangement in the neutral inclusion complex after oxidation.
Cui
Lu
L
Center for Supramolecular Science and Department of Chemistry, University of Miami, Coral Gables, Florida 33124-0431, USA.
Gadde
Suresh
S
Li
Wei
W
Kaifer
Angel E
AE
D001952:Bridged-Ring Compounds / Q000737:chemistry*; D055664:Electrochemical Techniques; D005296:Ferrous Compounds / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry*; D046911:Macromolecular Substances / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D000075163:Metallocenes; D015394:Molecular Structure; D010084:Oxidation-Reduction; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils
D001952:Bridged-Ring Compounds; D005296:Ferrous Compounds; D007093:Imidazoles; D046911:Macromolecular Substances; D000075163:Metallocenes; C456276:cucurbit(7)uril; D047028:Macrocyclic Compounds; D000099246:Cucurbit(n)urils; C004998:ferrocene