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A Simple Chemical Tuning of the Effective Concentration: Selection of Single‐, Double‐, and Triple‐Stranded Binuclear Lanthanide Helicates
Author(s) -
Terazzi Emmanuel,
Guénée Laure,
Bocquet Bernard,
Lemonnier JeanFrançois,
Dalla Favera Natalia,
Piguet Claude
Publication year - 2009
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200902026
Subject(s) - lanthanide , crystallography , ligand (biochemistry) , chemistry , intermetallic , stereochemistry , organic chemistry , receptor , ion , biochemistry , alloy
The replacement of terminal 2‐benzimidazol‐6‐carboxypyridine (two internal rotational degrees of freedom) with 2‐benzimidazol‐8‐hydroxyquinoline (one internal rotational degree of freedom) into segmental bis‐tridentate ligands in going from L2 and [ L3 ‐2 H] 2− to [ L12 b ‐2 H] 2− does not significantly affect the structures of the resulting binuclear lanthanide triple‐stranded helical complexes [Ln 2 ( L2 ) 3 ] 6+ , [Ln 2 ( L3 ‐2 H) 3 ], and [Ln 2 ( L12 b ‐2 H) 3 ] (palindromic helices, intermetallic contact distance≈9 Å, helical pitch≈1.4 nm per turn). However, their thermodynamic assemblies are completely different in solution, as evidenced by the spectacular decrease of the effective concentrations by two orders of magnitude for [ L12 b ‐2 H] 2− . This key parameter in the [Ln 2 ( L12 b ‐2 H) n ] ( n =2, 3) complexes is further abruptly modulated along the lanthanide series (Ln=La to Lu), which provides an unprecedented tool for 1) tuning the number of ligand strands in the final helicates, 2) selectively coordinating lanthanides in the various complexes, and 3) controlling the ratio of lanthanide‐containing polymers over discrete assemblies.