Manganese sites

It is interesting to note that these complexes are mixed-valent MnmMnIV complexes. Based on the relative structural data [the bond distances of the MnA atom are shorter than those of MnB], it has been concluded that in [Mn202(bipy)4]3+ one of the manganese ions is in the oxidation state IV [Mn(B)] and the other in the oxidation state III [Mn(A)]. Hence, the complex would have to be classified as a mixed-valent derivative with localized charge (Robin-Day Class I). Conversely, the two manganese sites are identical in [Mn202(phen)4]" +, from which one can infer that the charge is delocalized over the two centres (Robin-Day Class III). 

In the absence of suitable crystals for an X-ray structural study, combinations of FTIR, RR, XAS, EPR, ENDOR, XANES, and ESEEM spectroscopies were used to characterize the manganese site in the OEC. Vibrational spectroscopy, particularly low-frequency FT infrared and... 

VIII. OTHER BIOLOGICAL MANGANESE SITES VIII.A. Thiosulfate Oxidizing Enzyme... 

Several attempts have been made to stabilize the layered LiMn02 phase by substitution of manganese ions with small amounts of chromium and aluminum by conventional solid state reaction and the introduction of cobalf and nickel on the manganese sites via the chimie douce reaction. Although these substituted layered compounds resulted in improvements in capacity retention in comparison to pure LiMn02, they have been found to be thermodynamically unstable with respect to their transformation to the less desired spinel structure. 

The outputs of some mixed potential-type chemical sensors correlate with the type of electronic defect (i.e., n-type versus p-type), so the response has been attributed to the semiconducting behavior of the electrode material [314]. LaFeO3, which has been used as a semiconductor-type gas sensor ] 315, 316], has also been used as an electrode with YSZ [255, 263, 317] or NASICON ]317, 318] electrolytes for potentiometric NO, sensors. Strontium (i.e., (La,Sr)FeO3 ]255, 256, 284]) or strontium and cobalt (i.e., (La, Sr)(Co,Fe)O3 ]275, 280, 309]) have been added to LaFeO3 to improve electrode performance. (La,Ca)MnO3 doped with either cobalt or nickel on the manganese site has been used as the electrode for N O, sensors ]319]. The outputs of some NO, sensors with perovskite electrodes are shown in Figure 13.26 ]255, 256, 264, 275, 309, 312]. 

Fig. 29a-c. Schematic representations of the Mn and Cu sites in Mn Cup, PS3 (x = 0.13) a) XRD-averaged site b) manganese site c) copper site. The centre to sulfur distance of 2.83 A is calculated with the assumption that the three types of sites, [MnS6], XRD-averaged octahedron and [S3CU. .. CUS3] are homothetic... 

I. The photolysis of co-ordinated water in [ MnL-H2O) 2][C10j2 (L = dianion of tetradentate 02N2-donor Schiff bases). A model for the manganese site in photosystem II of green plant photosynthesis, J. Chem. Soc., Dalton Trans., p. 1391. 

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