Tuning facial-meridional isomerisation in monometallic nine-co-ordinate lanthanide complexes with unsymmetrical tridentate ligands

Dalton Transactions : an International Journal of Inorganic Chemistry
Thierry Le BorgneClaude Piguet

Abstract

The unsymmetrical tridentate benzimidazole-pyridine-carboxamide units in ligands L1-L4 react with trivalent lanthanides, Ln(III), to give the nine-co-ordinate triple-helical complexes [Ln(Li)3]3+ (i = 1-4) existing as mixtures of C3-symmetrical facial and C1-symmetrical meridional isomers. Although the beta13 formation constants are 3-4 orders of magnitude smaller for these complexes than those found for the D3-symmetrical analogues [Ln(Li)3]3+ (i = 5-6) with symmetrical ligands, their formation at the millimolar scale is quantitative and the emission quantum yield of [Eu(L2)3]3+ is significantly larger. The fac-[Ln(Li)3]3+ <--> mer-[Ln(Li)3]3+ (i = 1-4) isomerisation process in acetonitrile is slow enough for Ln = Lu(III) to be quantified by 1H NMR below room temperature. The separation of enthalpic and entropic contributions shows that the distribution of the facial and meridional isomers can be tuned by the judicious peripheral substitution of the ligands affecting the interstrand interactions. Molecular mechanics (MM) calculations suggest that one supplementary interstrand pi-stacking interaction stabilises the meridional isomers, while the facial isomers benefit from more favourable electrostatic contributions. As a result...Continue Reading

References

Feb 19, 2002·Chemical Reviews·Claude PiguetGérard Hopfgartner
Jun 13, 2002·Chemical Reviews·Jean-Claude G Bünzli, Claude Piguet
Jun 13, 2002·Chemical Reviews·Koen Binnemans, Christiane Görller-Walrand
Jul 18, 2002·Chemical Communications : Chem Comm·Nicolas AndréJean-Claude G Bünzli
Jan 30, 2003·Journal of the American Chemical Society·Marcel UtzFotios Papadimitrakopoulos
Jun 12, 2003·Journal of the American Chemical Society·Arnold B TamayoMark E Thompson
Jun 18, 2003·Chemical Communications : Chem Comm·Stéphane SuárezJean-Claude G Bünzli
Dec 16, 2003·Chemical Society Reviews·Jérôme Lacour, Virginie Hebbe-Viton

❮ Previous
Next ❯

Citations

Sep 6, 2012·Inorganic Chemistry·Patrick E RyanClaude Piguet
Sep 5, 2015·Inorganic Chemistry·Nail M ShavaleevJean-Claude G Bünzli
Jun 30, 2007·Chemistry : a European Journal·Thomas B JensenJean-Claude G Bünzli
Sep 18, 2009·Dalton Transactions : an International Journal of Inorganic Chemistry·Natalia Dalla FaveraClaude Piguet
Oct 22, 2009·Chemistry : a European Journal·Thomas Riis-JohannessenClaude Piguet
Feb 16, 2008·Dalton Transactions : an International Journal of Inorganic Chemistry·Thomas B JensenJean-Claude G Bünzli
Oct 18, 2012·Dalton Transactions : an International Journal of Inorganic Chemistry·C Allen ChangYeou-Guang Tsay
Jan 7, 2010·Inorganic Chemistry·Jean-François LemonnierClaude Piguet
Nov 20, 2014·Inorganic Chemistry·Lilit Aboshyan-SorghoClaude Piguet

❮ Previous
Next ❯

Related Feeds

Anthelmintics

Anthelmintics or antihelminthics are a group of antiparasitic drugs that expel parasitic worms (helminths) and other internal parasites from the body by either stunning or killing them and without causing significant damage to the host. Discover the latest research on anthelmintics here.