Cryptands neodymium

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). 

The ratio of the size of the metal ion and the radius of the internal cavity of the macrocyclic polyether determines the stoichiometry of these complexes. The stoichiometry of these complexes also depends on the coordinating ability of the anion associated with the lanthanide. For example, 12-crown-4 ether forms a bis complex with lanthanide perchlorate in acetonitrile while a 1 1 complex is formed when lanthanide nitrate is used in the synthesis [66]. Unusual stoichiometries of M L are observed when L = 12 crown-4 ether and M is lanthanide trifluoroacetate [67]. In the case of 18-crown-6 ligand and neodymium nitrate a 4 3 stoichiometry has been observed for M L. The composition of the complex [68] has been found to be two units of [Nd(18-crown-6)(N03)]2+ and [Nd(NCh)<--)]3. A similar situation is encountered [69] when L = 2.2.2 cryptand and one has [Eu(N03)5-H20]2- anions and [Eu(2.2.2)N03]+ cations. It is important to note that traces of moisture can lead to polynuclear macrocyclic complexes containing hydroxy lanthanide ions. Thus it is imperative that the synthesis of macrocyclic complexes be performed under anhydrous conditions. 

Faulkner, S., Beeby, A., Carrie, M.-C., et al. (2001) Time-resolved near-lR Itrminescence from ytterbirrm and neodymium complexes of the Lehn cryptand. Inorganic Chemical Communications, 4, 187. 

Although not particularly designed to be a pH-sensitive luminescent probe, Beeby et al. described a phenanthridine-carrying water-soluble Yb complex, in which the photosensitisation mechanism is switched as a functi(m of pH [93], A crown ether-modified neodymium(III) cryptand was proposed for barium ion detection [94], but as with many prototype cation sensors, the probe only works in acetonitrile. Moreover, the complex necessitates ultraviolet excitation, which removes one of the main advantages of using NIR luminescent lanthanide complexes. 

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