Complexation, electrochemically induced

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... 

The Archetype Electrochemically Induced Ring Gliding Motions in a Two-Geometry Copper-Complexed Catenanes... 

A recent development31 is the preparation of metal polymer complexes directly on the electrode via the electrochemically induced polymerization of the metal complex. Ruthenium(II) and osmium(II) complexes with ligands containing aromatic amines, e.g. 3- or 4-aminopyridine or 5-amino-1,10-phenanthroline, are electrochemically polymerized to yield a film of the metal polymer on the electrode surface. The polymerization involves free radicals, which are formed via the initial oxidation of the metal complex to a radical cation and subsequent reaction of the radical cation with a base to yield the free radical. 

Fig. 10 Principle behind electrochemically induced molecular motion in a copper(l) complex pseudorotaxane. The stable, four-coordinate, monovalent complex is oxidized to an intermediate tetrahedral, divalent species. This compound undergoes a rearram gementto afford the stable, five-coordinate...

The electrochemical behavior of 14+ is particularly clean and interesting, since only the 4- and the 5-coordinate geometries can be obtained on translating the metal-complexed ring from the phen site to the terpy site)841 The electrochemically induced molecular motions (square scheme1851), similar to those represented in Figure 10 but now involving stopped compounds, can be monitored by cyclic voltammetry (CV) and controlled potential electrolysis experiments)851... 

An interesting example of sullur-bridged systems is shown in equation (27). The disulftir-bridged dianion does not contain a metal bond. Chemical or electrochemical oxidation generates the neutral species that does have a metal metal bond. This process of electrochemically induced changes in bond order will be discussed below for porphyrin complexes as well. 

Figure 19. Electrochemically induced dethreading/rethreading of the self-complexing compound 28 + (MeCN, 298 K) [36],...

Recently, Schuhmann et al. reported ethanol biosensors by entrapping quinohemoprotein alcohol dehydrogenase and Os-complex-modified poly(vinyl imidazole) during the electrochemically induced deposition of the poly(acrylate)-based resin [80]. The sensor exhibited its efficiency and also sufficient stability for practical applications. Author claims that the reported sensor preparation process is simple, easy to control, oxygen insensitive and can be applicable to other enzyme sensors. 

Electrochemically induced cis-to-trans postitional stereoisomerization of ligands has been found on oxidation-reduction of several types of octahedral complexes of groups VIIB metals [510-519]. The key step is isomerization of cationic cw-intermediates formed by one-electron oxidation. 

Fig. 10. Principle of the electrochemically induced molecular motions in a copper complex rotaxane. The stable 4-coordinate monovalent complex [top left, the black circle represents Cu(I)] is oxidized to an intermediate tetrahedral divalent species [top right, the white circle represents Cu(II)]. This compound undergoes a complete reorganization process to afford the stable 5-coordinate Cu(II) complex [bottom right]. Upon reduction, the 5-coordinate monovalent state is formed as a transient [bottom left]. Finally, the latter undergoes the conformational change which regenerates the starting complex...

Electrochemically Induced Failures. The electrochemical failure mechanisms accelerated by temperature, humidity, and electrical bias that were described in Sec. 57.2.1.3 for printed circuit boards also apply to the remainder of the PCA. The solder used for the interconnects and the metal component terminations and lead frame finishes can also be involved in the reactions. The large number of dissimilar metals increases the complexity of the situation and the possibility of galvanic corrosion in a humid environment. In addition, contaminants introduced during printed circuit assembly such as flux residues can contribute to the failures. 

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