Rate constants cyclophane

Fig.6Tcmpcr tufe dependence of fcorieouiionalraie constants Fjj.7 Temperature dependence of reorientational rate constants of HNMA ID PMMA. (—) e-ftlaxanoo (dielectric relaxation) cyclophane in PMMA.(—) P-relaxation (dielectric relaxation) f—) y-relaxation ( CP / MAS CNMR) For cotnparisoo. For comparison, the relaxation frequencies of these data have the reluation frequencies of these dau have been shifted been shifted by an appropriate amount along the ordinate, by an appropriate amount along tbe ordinate. 

Sufllce it to state that in contrast to 22a the imidazolyl-substituted cyclophanes 22b and 22 c indeed catalyze the hydrolysis of aliphatic carboxylic activated esters, 22 c being a little more effective. The efficiency as represented by the ratio of pseudo first order rate constants of the catalyzed versus the uncatalyzed reaction k Jk a displayes a sharp maximum with the ester of tetradecanoic acid [22c] 100), whereas... 

Supramolecular assemblies/architectures represent an alternative approach to electrically connecting redox proteins with electrodes. For example, bis-bipyridinium cyclophane has been threaded onto a molecular wire assembled on an electrode by the formation of an intermediary pdonor-acceptor bond with the bis-imine-benzene site of the molecular wire [4]. The wire was then stoppered by an adamantane stopper unit to form a supramolecular assembly. The charged cyclophane could then be moved along the wire by electrochemi-cally changing its oxidation state. Reduction of the cyclophane to the bis-radical cation removed the electron acceptor properties of the threaded ring, and the reduced acceptor was electrostatically attracted by the electrode. This resulted in translocation of the reduced cyclophane to the electrode with a rate constant corresponding to k = 320 s. Oxidation of the reduced cyclophane reversed the direction of movement. 

Alternatively, NMR or UV-Vis spectroscopy can be used to determine association and dissociation rate constants, and thence estimate association constants, as in the study of the threading of L1074 through L1058 [194]. Kinetic and equilibrium characteristics of association have also been monitored for model systems in which 1,4-disubstituted benzenes interact with the ubiquitous cyclophane LI058 (1951. 

---