AUTHOR=Deiters Emmanuel , Eliseeva Svetlana V., Bünzli Jean-Claude G.

TITLE=Self-assembly of a helical zinc-europium complex: speciation in aqueous solution and luminescence

JOURNAL=Frontiers in Chemistry

VOLUME=1

YEAR=2013

URL=https://www.frontiersin.org/journals/chemistry/articles/10.3389/fchem.2013.00015

DOI=10.3389/fchem.2013.00015

ISSN=2296-2646

ABSTRACT=<p>Two new tridentate(NNO)-bidentate(NN) compartmental ligands, HL<sup>5</sup> and HL<sup>6</sup>, are synthesized from pyridine and benzimidazole synthons. They react in aqueous solution under physiological conditions with Zn<sup>II</sup>, Ln<sup>III</sup>, or a mixture thereof, to yield complexes of different stoichiometries, 1:3, 2:2, 2:3, 1:1:3, the speciation of which is established by UV-visible titrations and ESI mass spectrometry. Photophysical studies of the Eu<sup>III</sup>-containing solutions in Tris-HCl 0.1 M (pH = 7.4) show that lanthanide luminescence arises from a unique N<sub>6</sub>O<sub>3</sub> coordination site with pseudo <italic>D</italic><sub>3</sub> symmetry. Relevant parameters such as crystal field splitting, lifetime, radiative lifetime, and intrinsic quantum yield perfectly match those reported for dinuclear 4f-4f helicates in which the Eu<sup>III</sup> ion has the same coordination environment.</p>