Electrochemically induced structural

This study clearly demonstrates that by using the differencing technique, sufficient sensitivity is achieved to permit the study of electrochemically induced structural changes in thin surface films. The results obtained indicate that it should be possible to study films of about 100-A thickness fairly easily with a small, fixed anode X-ray source, with such a system probably requiring less than 24 hours of data acquisition time. The study of adsorbed monolayers clearly will be more difficult. Such investigations will benefit from the use of high-surface-area electrodes, e.g., platinum black, and/or the use of the Laue geometry. 

An example of electrochemically induced trans— cis isomerization is given by the macrocyclic complex rra j-[MnnI(cyclam)Cl2]+, the molecular structure of which is illustrated in Figure 9.9... 

Although the redox reactions in Sch. 12 have not been achieved electrochemically, they illustrate another type of redox-induced structural change in a dimolybdenum compound with a sulfur-rich coordination sphere. In this case, Mo2(/r-S)2 ring opening in 18 (cleavage of Mo—Mo and Mo—S bonds) is associated with the exposure of vacant coordination sites, and the uptake of two carbonyl ligands in 17 [7, 53]. 

The kinetics of Hg UPD in acetate media is clearly slower than in the previous media, as voltammetric and chronoamper-ometric measurements have revealed [26]. A delicate interplay between the presence of the strongly interacting anions and kinetics and structure of electrochemically induced phase transitions has been shown. 

Figure 13.26 Structure formula of rotaxane 294+ and the electrochemically induced shuttling of the cyclophane along the dumbbell-shaped component (CH3CN, 298 K).

Kochi s book from 1978 [la] helped to establish electron-transfer and radical reactions as a crucial part of mainstream organometallic chemistry. The importance of such reactions is evident from Astruc s book [lb], still the most comprehensive and authoritative book in the area, and from several reviews and review collections [2] on aspects of organometallic electron-transfer reactivity. This chapter will be fully devoted to the use of electrochemical techniques to obtain bond-energy data for organometallic complexes, a topic that has not been previously reviewed. Aspects of the energetics of redox-induced structural changes and isomerizations, a thoroughly pursued topic, has been reviewed [2o] and will not be included here. 

P. C. Eklund, J. M. Holden, and A. M. Rao, Springer Ser. Solid-State Sci., 1997,124 (Relaxations of Excited States and Photo-Induced Structural Phase Transitions), 256. D. M. Guldi, M. Maggini, S. Mondini, G. Scorrano, and M. Prato, Proc. -Electrochem. Soc., 1996, 96 (Recent Advances in the Chemistry and Physics of Fullerenes and Related Materials, Vol. 3),%9. 

BusSnH-mediated intramolecular arylations of various heteroarenes such as substituted pyrroles, indoles, pyridones and imidazoles have also been reported [51]. In addition, aryl bromides, chlorides and iodides have been used as substrates in electrochemically induced radical biaryl synthesis [52]. Curran introduced [4-1-1] annulations incorporating aromatic substitution reactions with vinyl radicals for the synthesis of the core structure of various camptothecin derivatives [53]. The vinyl radicals have been generated from alkynes by radical addition reactions [53, 54]. For example, aryl radical 27, generated from the corresponding iodide or bromide, was allowed to react with phenyl isonitrile to afford imidoyl radical 28, which further reacts in a 5-exo-dig process to vinyl radical 29 (Scheme 8) [53a,b]. The vinyl radical 29 then reacts in a 1,6-cyclization followed by oxidation to the tetracycle 30. There is some evidence [55] that the homolytic aromatic substitution can also occur via initial ipso attack to afford spiro radical 31, followed by opening of this cyclo-... 

Many electrochemically dopant-induced structure-property changes in conducting polymers have been described for use in, for example, electrochromic windows and displays, electrochemically controlled chemical separation and delivery systems, redox capacitors, electromechanical actuators, etc.,32. Some of these are apparently close to commercial application. Polypyrrole capacitors are already in conunercial production,27. 

These probes were, however, found to be very effective for high-resolution mapping of topographical and structural changes of a substrate immersed in fluid, in response to a local chemical perturbation (induced electrochemically). In particular, the probes were used to electrochemically induce dissolution from a specific region of... 

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