“…Scandium(III) is the smallest among rare earths: its ionic radius of 0.74 Å is 0.12 Å smaller than that of lutetium(III) (Shannon, 1976). The large difference in ionic radius between scandium and other rare earths leads to special properties and reactivity of scandium complexes (Moeller et al, 1965;Zimmermann and Anwander, 2010). This is best illustrated by the product from the co-condensation of scandium metal and 1,3,5-t-Bu3C6H3 (Cloke et al, 1991).…”
Rare earth chemistry has witnessed remarkable advances in recent years. In particular, ancillary ligands other than cyclopentadienyl derivatives have been introduced to the organometallic chemistry and their complexes exhibit distinct reactivity and properties compared to the metallocene or half-sandwiched analogues. The present chapter reviews arene-bridged rare earth complexes with an emphasis on those compounds obtained by reduction reactions. A particular emphasis is placed on rare earth complexes supported by 1,1′-ferrocenediyl diamides since they show the most diverse chemistry with arenes: fused arenes, such as naphthalene and anthracene, formed inverse-sandwiched complexes, in which the arene is dianionic; weakly conjugated arenes, such as biphenyl, p-terphenyl, and 1,3,5-triphenylbenzene, were unexpectedly reduced by four electrons and led to 6-carbon, 10- electron aromatic systems; on the contrary, (E)-stilbene, which has a carbon-carbon double bond between the two phenyl rings, could only be reduced by two electrons, which were located on the carbon-carbon double bond instead of the phenyl rings.
“…Scandium(III) is the smallest among rare earths: its ionic radius of 0.74 Å is 0.12 Å smaller than that of lutetium(III) (Shannon, 1976). The large difference in ionic radius between scandium and other rare earths leads to special properties and reactivity of scandium complexes (Moeller et al, 1965;Zimmermann and Anwander, 2010). This is best illustrated by the product from the co-condensation of scandium metal and 1,3,5-t-Bu3C6H3 (Cloke et al, 1991).…”
Rare earth chemistry has witnessed remarkable advances in recent years. In particular, ancillary ligands other than cyclopentadienyl derivatives have been introduced to the organometallic chemistry and their complexes exhibit distinct reactivity and properties compared to the metallocene or half-sandwiched analogues. The present chapter reviews arene-bridged rare earth complexes with an emphasis on those compounds obtained by reduction reactions. A particular emphasis is placed on rare earth complexes supported by 1,1′-ferrocenediyl diamides since they show the most diverse chemistry with arenes: fused arenes, such as naphthalene and anthracene, formed inverse-sandwiched complexes, in which the arene is dianionic; weakly conjugated arenes, such as biphenyl, p-terphenyl, and 1,3,5-triphenylbenzene, were unexpectedly reduced by four electrons and led to 6-carbon, 10- electron aromatic systems; on the contrary, (E)-stilbene, which has a carbon-carbon double bond between the two phenyl rings, could only be reduced by two electrons, which were located on the carbon-carbon double bond instead of the phenyl rings.
“…However, these chelators have extremely high affinity for Tb 3ϩ and other lanthanide ions (stability constants Ͼ10 15 M Ϫ1 ) (14). It is not feasible to achieve the desired Tb 3ϩ concentrations in the presence of any of these Ca 2ϩ chelators.…”
Section: Although Lanthanide Ions Including Tbmentioning
Small conductance Ca 2؉ -activated K ؉ (SK) channels sense intracellular Ca 2؉ concentrations via the associated Ca 2؉ -binding protein calmodulin. Structural and functional studies have revealed essential properties of the interaction between calmodulin and SK channels. However, it is not fully understood how the binding of Ca 2؉ to calmodulin leads to channel opening. Drawing on previous biochemical studies of free calmodulin using lanthanide ions as Ca 2؉ substitutes, we have used the lanthanide ion, Tb 3؉ , as an alternative ligand to study the activation properties of SK channels. We found that SK channels can be fully activated by nanomolar concentrations of Tb 3؉ , indicating an apparent affinity >100-fold higher than Ca 2؉ . Competition experiments show that Tb 3؉ binds to the same sites as Ca 2؉ to activate the channels. Additionally, SK channels activated by Tb 3؉ demonstrate a remarkably slow deactivation process. Comparison of our results with previous biochemical studies suggests that in the intact SK channel complex, the N-lobe of calmodulin provides ligand-binding sites for channel gating, and that its ligand-binding properties are comparable to those of the N-lobe in isolated calmodulin.lanthanide ͉ EF hand ͉ gating ͉ calcium-activated potassium channel
“…We suggest that the oxygen-species formed on the SWNTs in the latter case are responsible for the residual metal. Rare earth metal ions coordinate preferentially to oxygen donors rather than to nitrogen donors [34]. This will lead to competition for the catalyst metals between the aminocarboxylic acid ligands and the grafted functional groups on SWNTs.…”
Section: Cydta Is Larger Than That In the S A M P L E P U R I F I E Dmentioning
A method for the non-destructive purification of single-walled carbon nanotubes (SWNTs) using classical coordination chemistry to remove the metal catalyst has been developed. In preliminary tests, the conductivity of fi lms based on the resulting SWNTs was markedly better than that of fi lms prepared from SWNTs purifi ed by treatment with oxidizing acid solutions. The transparent and conducting SWNT fi lms have potential applications in optoelectronic devices.
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