Spectroscopic Study of the Hydration Equilibria and Water Exchange Dynamics of Lanthanide(III) Complexes of 1,7-Bis(carboxymethyl)-1,4,7,10-tetraazacyclododecane (DO2A)
✍ Scribed by Fabrice Yerly; Frank A. Dunand; E´´va Tóth; Artur Figueirinha; Zoltán Kovács; A. Dean Sherry; Carlos F. G. C. Geraldes; André E. Merbach
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 315 KB
- Volume
- 2000
- Category
- Article
- ISSN
- 1434-1948
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✦ Synopsis
The hydration state of a series of [Ln(DO2A)(H 2 O) n ] + complexes in aqueous solution at pH = 6.4-7.0 was studied by measuring the lanthanide-induced 17 O shifts (LIS) of water [Ln includes elements from Ce to Yb; DO2A = 1,7-bis(carboxymethyl)-1,4,7,10-tetraazacyclododecane]. Their contact contribution, obtained from Reilley plots, indicated a decrease in the inner-sphere water coordination number of the [Ln(DO2A)(H 2 O) n ] + complexes from n = 3 (Ce-Eu), to n = 2 (Tb-Yb). A temperature-dependent UV/Vis absorption study of the 578-582 nm 7 F 0 Ǟ 5 D 0 transition band of [Eu(DO2A)(H 2 O) n ] + in aqueous solution showed that this complex is present in an equilibrium between eight-and nine-coordinate species with n = 2 and n = 3, respectively. The hydration equilibrium parameters (2 o 3), K 2-3 298 = 4.0 ± 0.2, ∆H 2-3 0 = -12.1 ± 1 kJ mol -1 and ∆S 2-3 0 = -28.9 ± 3 J mol - 1 K -1 ,correspond to an average hydration number of 2.65-