Measurement of the Dissociation of Eu^II-Containing Cryptates Using Murexide

Abstract

Dissociation rates of five Eu II -containing cryptates in water were measured using UV-visible spectroscopy and murexide at pH 6.5, 7, 7.5, 8, and 9. Murexide was used as a coordinating dye for Eu II . Results for a known cryptate were within experimental error of the value obtained using other methods, and enabled measurement of other cryptates. This validation of the use of murexide to study the dissociation of Eu II -containing cryptates enables use with other complexes of Eu II .

Rational Design of High‐Relaxivity EuII‐Based Contrast Agents for Magnetic Resonance Imaging of Low‐Oxygen Environments

“…For complexes 1 and 3 , the longest Eu II −O bond involves a catecholic oxygen atom. The Eu II −OH 2 distances in 1 are 2.562(3) and 2.578(3) Å, which are also consistent with other observations [22b, 23d] . The internuclear distance between the two Eu II ions in 1 is 9.748 Å.…”

Expanding the Coordination of f-Block Metals with Tris[2-(2-methoxyethoxy)ethyl]amine: From Molecular Complexes to Cage-like Structures

“…Coordination of thiocyanate in place of triflate ions changes the geometry from a sphenocorona to a staggered dodecahedron (Shape analysis: Table S64). The ten-coordinate Eu II -cryptates formed in the presence of nitrate, triflate, or thiocyanate anions are in contrast to the reported nine-coordinate cryptates of Eu II , and Eu II -containing nitrogenous cryptates, ,,,− showcasing that chelation of Eu II by 1 leaves two open coordination sites that can be filled by counterions or solvent molecules, with the overall coordination number being dependent on the size of the counterions or solvent molecules.…”

“…Although the analogous oxygen atom in nine-coordinate Eu II 1 cryptates lies on the hexagonal plane containing the two nitrogen donors and three of the remaining five oxygen atoms of 1, in Eu II 2, one of the oxygen atoms (OCH 3 ) is in a trigonal plane. In all [Eu II 2X(S)] + cations (X = Cl, Br, or I; S = CH 3 OH or THF), one halide ion fills the vacancy typically occupied by the second nitrogen donor of 48 and consistent with Eu in the divalent oxidation state. Eu−O (ether) and Eu−N (amine) distances are, on average, similar across all nine-and ten-coordinate complexes of Eu II 2 (Table 1) and within the same order of ] 0.17 and other reported cryptates of Eu II 1.…”

Solid-state and solution-phase characterization of SmII-aza[2.2.2]cryptate and its methylated analogue

“…The blue-shifted absorptions of [Sm 2 ]I 2 relative to [Sm 1 I]I are consistent with reported spectra of [Eu 1 I]I 2 and [Eu 2 ]I 2 in methanol that show similar trends. 27–29 Thus, it is likely that the observed blue-shifted UV-visible absorptions of [Sm 2 ]I 2 are a result of differences in geometry between [Sm 1 I]I and [Sm 2 ]I 2 in solution, similar to [Eu 1 I]I and [Eu 2 ]I 2 . 34 Altogether, the UV-visible data suggest similar coordination environments for [Sm 2 ]I 2 in both solvent media.…”

“…One such group of Ln II complexes that have been the subject of extensive investigation with regard to their structural, photophysical, and electrochemical properties is the Ln II -cryptates. 2,[26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] In many studies, cryptands such as 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo [8.8.8]hexacosane (222) and 5,6-benzo-4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo [8.8.8]hexacos-5-ene are used to encapsulate Ln II ions, [26][27][28][29][30][31][32][37][38][39][40][41][42] and reported Ln II -cryptates have luminescence and electrochemical properties that are useful in applications including light-emitting diodes, imaging, and catalysis. 2,35,43 The luminescence and electrochemical properties of Ln II -cryptates are dependent on both the Ln II ion and the type of donor atoms in the cryptand.…”