Unusual nitro-coordination of europium(iii) and terbium(iii) with pyridinyl ligands

Abstract

A new ligand family based on picoline, bipyridine and terpyridine containing a nitro moiety has been synthesized and its coordination and sensitization ability for lanthanide ions has been studied. Three new complexes were characterized by X-ray single crystal diffraction and all three show uncommon coordination of the nitro moiety to the lanthanide ion. 5cTb, a terpyridine-nitro derivative with Tb(NO₃)₃, crystallizes in the orthorhombic space group Pbca with a = 15.125(3), b = 13.776(3), c = 18.716(4) Å, and V = 3899.8(13) ų and is isostructural with its Eu(III) analog (5cEu) with cell parameters a = 15.1341(4), b = 13.7070(4), c = 18.8277(5) Å. 6Eu, a tripodal amine with a nitro-derivatized pyridine with Eu(CF₃SO₃)₃, crystallizes in the triclinic space group P with a = 11.067(2), b = 11.633(2), c = 12.772(3) Å, α = 110.94(3), β = 97.49(3), γ = 91.42(3)° and V = 1518.1(5) ų. Finally, ligand 5a, a bipyridine-nitro derivative, crystallizes in the orthorhombic space group P2₁/n with a = 3.7128(3), b = 11.7806(8), c = 19.9856(14) Å, β = 92.925(2)° and V = 873.01(11) ų. All four ligands show sensitization of Eu(III) and Tb(III) luminescence.