Structures of Rare Earth Homodinuclear Macrocyclic Complexes with the Polyamine Polycarboxylic Ligand 1,4,7,10,14,17,20,23-Octaazacyclohexacosane-1,4,7,10,14,17,20,23-octaacetic Acid (H8OHEC) in the Crystal and in Solution

Rigid MIIL2Gd2III (M = Fe, Ru) Complexes of a Terpyridine-Based Heteroditopic Chelate: A Class of Candidates for MRI Contrast Agents

“…Putting two gadolinium(III) ions in close neighborhood may influence the electronic relaxation parameters of the complex: the intramolecular vicinity of two Gd III ions can induce an increase of the transverse electronic relaxation rates, 1/ T 2e , and, consequently, a decrease in the relaxivity of the whole complex . The crystallographic X-ray structure of Na 2 [Gd 2 (OHEC)(H 2 O) 2 ]·12H 2 O (Figure ) lead to a Gd−Gd distance of 6.5 Å, and therefore a r 1 of only 3.5 mM -1 s -1 has been measured at 20 MHz and 37 °C for this complex . We previously mentioned that the electronic relaxation rates mainly depend on ZFS.…”

Being Excited by Lanthanide Coordination Complexes: Aqua Species, Chirality, Excited-State Chemistry, and Exchange Dynamics

“…Concerted arm rotation is also believed to be the salient dynamic process occurring in lanthanide complexes of expanded polyazamacrocyclic-substituted ligands. Thus, with the dimeric Y 3+ complex of the octa(aza-acetate), OHEC (Chart 3), 1 H-ROESY studies indicated an interconversion between a centrosymmetric major isomer and an asymmetric minor isomer (Δ G 300 65 kJ mol -1 ) that may well involve rotation of the acetate groups …”

“…While the variation of ligand O-Ln and N-Ln distances faithfully follow the ionic radius change, 23 the Ln-OH 2 distances do not (Figure 6). The Ln-OH 2 distances were found to vary with the crystal form 21 2.815(6) twisted square antiprism RUHMIQ 22 2.66 (8) twisted square antiprism CIQYOQ(A) 24 2.650(6) twisted square antiprism KINDEQ(A) 25 2.634(6) square antiprism CIQYOQ(B) 24 2.625(6) twisted square antiprism KINDEQ(B) 25 2.626(6) square antiprism HAMZOK 26 2.597(6) tricapped trigonal prism ZEQVUM(A) 27 2.596(3) distorted tricapped trigonal prism ZEQVUM(B) 27 2.546(3) distorted tricapped trigonal prism ZAXZED 28 2.535(3) distorted tricapped trigonal prism LESPUU 29 2.534(2) distorted tricapped trigonal prism CEOVAV 30 2.526(6) irregular polyhedron HAMZAW 26 2.516( 4…”

“…Thus, with the dimeric Y 3+ complex of the octa(aza-acetate), OHEC (Chart 3), 1 H-ROESY studies indicated an interconversion between a centrosymmetric major isomer and an asymmetric minor isomer (∆G 300 65 kJ mol -1 ) that may well involve rotation of the acetate groups. 114 The situation with acyclic ligands (e.g., DTPA and its substituted variants) is more complex and less well-defined. Two recent reviews have summarized our current understanding.…”

Unusual seeding mechanism for enhanced performance in solid-phase magnetic extraction of Rare Earth Elements

“…The majority of structurally characterized complexes of REE with amino carboxylate ligands, however, have been produced at elevated pH (in the range 8.5–10), featuring chelation with involvement of amino groups into complexation383940. It is thus surprising that very little has been studied so far about adsorption by nanomaterials under different pH conditions.…”