Europium-directed self-assembly of allyl bis(triazolyl)pyridine (btp) ligands.

Two allyl-appended 2,6-bis(1,2,3-triazol-4-yl)pyridine (btp) ligands 1 and 2 were synthesised and characterised, the latter a mannose-derivative. Both form luminescent europium(III) complexes with quantum yields 5.4% and 1.9%. Despite reporting previously the ability of ligand 1 to form self-templated [2]catenanes under ring-closing metathesis conditions (and 2 doing so in lower yields), attempts to form Eu(III)-centred catenanes from allyl-appended complexes were not successful due to geometrical and structural constraints. Self-assembly of both ligands with Eu(III) in acetonitrile was studied by UV-Vis absorbance and emission titrations, and for chiral carbohydrate-derivative 2, complementary circular dichroism titrations were also analysed. Stability constants were determined as log β1:3 = 20.9 and 22.6 respectively, for complexes [Eu·(btp)3]3+.