Coordination sphere lanthanides

It is well known, that in aqueous solutions the water molecules, which are in the inner coordination sphere of the complex, quench the lanthanide (Ln) luminescence in result of vibrations of the OH-groups (OH-oscillators). The use of D O instead of H O, the freezing of solution as well as the introduction of a second ligand to obtain a mixed-ligand complex leads to either partial or complete elimination of the H O influence. The same effect may be achieved by water molecules replacement from the inner and outer coordination sphere at the addition of organic solvents or when the molecule of Ln complex is introduced into the micelle of the surfactant. 

For elimination of intramolecular energy losses, we have synthesized ligands with high hydrophobisity - perfluoro-P-diketones R -CO-CH -CO-R, (R = CgF j or CgF R = phenyl or a-thienyl), that without second ligand eliminate completely water molecules from the inner coordination sphere. These ligands we have used in analysis at determination of Sm, Eu, Nd, Yb microamounts in high-purity lanthanide and yttrium oxides. 

The coordination chemistry of ancillary amidinate ligands with a pyridine functionality has been described. Magnesium, aluminum, zirconium, and lanthanum complexes have been prepared in which the amidinate anions act as tridentate, six-electron-donor ligands Amidinate ligands containing quinolyl substituents were constructed in the coordination sphere of lanthanide... 

On the other hand, lanthanides with 100% isotopical purity such as terbium or holmium are preferred to simplify the operation and minimize decoherence in spin qubits. In this respect, the existence, for some lanthanides, of a manifold of electronuclear states can provide additional resources for the implementation of multiple qubit states within the same molecule [31]. All atoms in the first coordination sphere should be oxygen, and the sample should be deuter-ated if the compound contains hydrogen, to avoid interaction with other nuclei spins. Again, POM chemistry has been shown to provide ideal examples of this kind. 

Figure 2. Dy(P30io)2 is a lanthanide shift reagent commonly used in biological 7Li NMR experiments. The Dy3+ ion has a coordination number of nine with two P3O10 moieties, acting as tetradentate ligands, and one molecule of H2O coordinated in the first coordination sphere up to seven Li+ ions can bind in the second coordination sphere.

Although no single crystal X-ray work has been done on the cyclopentadienide complexes of the trivalent actinides, it is clear that they have structures similar to those of the known homologous lanthanides. Both the trivalent lanthanides and actinides behave as Lewis acids and form adducts to complete their coordination spheres. An optimum formal coordination number of ten is indicated and their structures seem to be dictated by a maximization of electrostatic interactions within the steric constraints of the ligands. 

An approach other than steric hindrance has been used to overcome the previously mentioned instability of the actinide homoalkyls. It was found that the inclusion of jT-bonding ligands in the coordination sphere considerably enhanced the stability of the alkyl complex. Recently, the same line of reasoning has also yielded a new series of 7r-cyclopentadienyl lanthanide alkyls (C5H5)2LnR where Ln =Gd, Er, Yb and R = C=C, and CH3 120,121). The infrared data for these complexes are consistent with u-bonded structures and the room temperature magnetic susceptibilities are very close to the free ion values. The actinide complexes (75,... 

Recently, tris-p-diketiminate lanthanide complexes [LnL3 ] (X = Cl, L Ln = Pr 111, Nd 112, Sm 113 X = H, L Ln = Nd 114 X = Me, L Ln = Nd 115) (Scheme 12) displaying a high activity in producing PLAs under mild conditions via ROP of L-lactide have been reported. This reactivity may be attributed to the crowded coordination sphere around the central metal, which incidentally affords an activated Ln-N(p-diketiminate) bond. The activity depends on the central metals, and the active trend of Sm < Nd < Pr is consistent with the sequence of the ionic radii [113]. 

The effect of additives on Shibasaki s lanthanide-BINOL catalysts has been investigated by Inanaga and coworkers. From a variety of additives, triphenylphosphine oxide turned out to be the best one improving, for example, the obtained ee for the chalcone epoxide from 73% to 96% (Table 16) . The explanation for the positive effect of the additive was the disruption of the oligomeric structure of the catalyst by coordination of the phosphine oxide. As a consequence, epoxidation takes place in the coordination sphere of the ytterbium where the reaction site might become closer to the chiral binaphthyl ring due to the phosphine oxide ligand with suitable steric buUdness. In contrast to the Shibasaki... 

Recently, a series of derivative ligands, [L19]4-—[L23]4-, has been reported (32,62), where the acetophenone chromophore in [L18]4- is replaced by a dipyrazolylpyridine chromophore. These form lanthanide complexes that are stable in aqueous solution, and which possess very promising photophysical attributes. The europium and terbium complexes of all these ligands have long lifetimes (1.3-1.4 ms for europium and 2.3-2.8 ms for terbium) in water that are largely unchanged by solvent deuteration, indicating the effective exclusion of solvent from the primary coordination sphere. 

It is believed that the presence of small concentrations of water in the sulfuric acid solutions corresponds to a solution structure in which the H20 molecules are not in the first coordination sphere around the lanthanide ions. A further increase in the water, however, changes the structure of the solution. It is thought that the H2S04 in the first coordination sphere... 

In this section are discussed hydrates of lanthanide salts where the water molecules form a majority of the coordination sphere and where there is evidence concerning the number or... 

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