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Formation of Novel Dinuclear Lanthanide Luminescent Samarium(III), Europium(III), and Terbium(III) Triple‐Stranded Helicates from a C 2 ‐Symmetrical Pyridine‐2,6‐dicarboxamide‐Based 1,3‐Xylenediyl‐Linked Ligand in MeCN
Author(s) -
Comby Steve,
Stomeo Floriana,
McCoy Colin P.,
Gunnlaugsson Thorfinnur
Publication year - 2009
Publication title -
helvetica chimica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.74
H-Index - 82
eISSN - 1522-2675
pISSN - 0018-019X
DOI - 10.1002/hlca.200900213
Subject(s) - chemistry , lanthanide , samarium , terbium , europium , fluorescence , ligand (biochemistry) , metal , pyridine , crystallography , naphthalene , luminescence , stereochemistry , inorganic chemistry , medicinal chemistry , organic chemistry , receptor , ion , biochemistry , physics , optoelectronics , quantum mechanics
The synthesis of the C 2 ‐symmetrical ligand 1 consisting of two naphthalene units connected to two pyridine‐2,6‐dicarboxamide moieties linked by a xylene spacer and the formation of Ln III ‐based (Ln=Sm, Eu, Tb, and Lu) dimetallic helicates [Ln 2 ⋅ 1 3 ] in MeCN by means of a metal‐directed synthesis is described. By analyzing the metal‐induced changes in the absorption and the fluorescence of 1 , the formation of the helicates, and the presence of a second species [Ln 2 ⋅ 1 2 ] was confirmed by nonlinear‐regression analysis. While significant changes were observed in the photophysical properties of 1 , the most dramatic changes were observed in the metal‐centred lanthanide emissions, upon excitation of the naphthalene antennae. From the changes in the lanthanide emission, we were able to demonstrate that these helicates were formed in high yields ( ca. 90% after the addition of 0.6 equiv. of Ln III ), with high binding constants, which matched well with that determined from the changes in the absorption spectra. The formation of the Lu III helicate, [Lu 2 ⋅ 1 3 ], was also investigated for comparison purposes, as we were unable to obtain accurate binding constants from the changes in the fluorescence emission upon formation of [Sm 2 ⋅ 1 3 ], [Eu 2 ⋅ 1 3 ], and [Tb 2 ⋅ 1 3 ].