Item – Theses Canada

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OCLC number
1032908551
Link(s) to full text
LAC copy
Author
Yuan, Lina.
Title
Host-guest complexation based on cucurbiturils.
Degree
Queen's University, 2008
Publisher
Kingston : Queen's University, 2008.
Description
1 online resource
Notes
Includes bibliographical references.
Abstract
This thesis deals with the effects of host-guest complexation, based on cucurbit[n]uril (CB[n], n = 6, 7 and 8) host molecule, on the chemical, electrochemical and spectroscopic properties of the included guests. Both CB[6] and CB[7] form 1:1 complexes with [CH3bpy(CH2)6bpyCH]4+3, encapsulating the central hexamethylene chain. With its relatively larger cavity, a second CB[7] host will include one of the viologen units, forcing, through steric and electronic repulsions, the first CB[7] to abandon the inclusion of the central chain and move to the other viologen unit, thus forming a [3]pseudorotaxane. The inclusion of the two enantiomers of protonated N-benzyl-1-(1-naphthyl)ethylamine in the achiral CB[7] results in a five-fold increase in the molar optical rotation of {BNEAH���CB[7]}+ and significant changes in the longer wavelength band in the circular dichroism spectra, attributed to a restricted rotation of the naphthyl group about the chiral center upon inclusion of the benzyl portion of the guest in the CB[7] cavity. The effects of host-guest complexation of the (trimethylammonio)- methylferrocene(+/2+) couple (FcTMA+/2+) by CB[7] on the kinetics of its electron self-exchange and electron transfer reactions were investigated. The slow exchange of the ferrocene guest, allows for the simultaneous monitoring of the 1H NMR line-broadening for both the FcTMA++ and {FcTMA���CB[7]} species in the presence of the paramagnetic FcTMA2+; The electron self-exchange rate constant increases moderately upon inclusion of both reduced and oxidized species, while the rate constants for the oxidation of ferrocenes by the bis(2,6-pyridinedicarboxylato)cobaltate(III) ion (which does not bind to CB[7]), were significantly reduced a result of reduced thermodynamic driving forces and steric hindrance to close approach of the oxidant to the encapsulated ferrocenes. This work was extended to investigations of the inclusion of bis(ferrocene) guests, demonstrating that a sufficiently long linker is required to accommodate a CB[7] host on each ferrocene unit. The formation of stable host-guest complexes of the bent titanocene, TiCp2+(H22O)2, with both CB[7] and CB[8] were characterized in aqueous solution. The CB[8] formed a more stable complex than CB[7], contrary to the order observed with ferrocene guests, attributable to the larger radius of the bent titanocene guest.
Other link(s)
qspace.library.queensu.ca
Subject
cucurbiturils.