Barium cryptates

C20H35CaCl2NsOi8f Calcium perchlorate - diacetamide (1 5), 42B, 575 C20H3 8BaN, 07S2, Barium cryptate, 39B, 520... 

In order to accommodate the small, highly charged calcium ion, the cryptand adopts an unsymmetrical conformation in which two of the chains are pushed apart to allow coordination of a water molecule and the N N distance is reduced to 5.44 A (42). In the corresponding barium complex, the structural unit consists of two cryptates, two water molecules, and four thiocyanate anions, two of which (9) are bound through nitrogen to the metal, (43). 

Ligand 131 contains both cryptate and crown ether binding units. It reacts with neodymium triflate to give a 1 1 cryptate [Nd c 131]3+ exhibiting NIR luminescence upon excitation at 355 nm. The lifetime of the Nd(4F3/2) level is 347 and 711 ns in methanol and methanol-, respectively, which translates to MeOH 0 using eq. (10b). When barium ions are added to a solution of this complex in acetonitrile, the intensity of the 1.06 pm emission band is reduced substantially, while the lifetime of the Nd(4F3/2) level remains unchanged at about 470 ns. The Ndm ion is therefore not displaced from the cryptand cavity, while its luminescence is modulated by the presence of the Ba2+ ions bound by the crown ether (Coldwell et al., 2006). 

Table 2 Structural parameters for cryptate complexes of calcium and barium...

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