Lanthanide metal complexes of N,N′-ethylenebis(pyridin-2-one); from chelates to metallacyclic frameworks

Abstract

The ligand N,N′-ethylenebis(pyridin-2-one) (EBP) forms a range of lanthanide (Ln) complexes of types Ln(EBP) 2(NO 3) 3 (Ln = La-Gd), Ln 2(EBP) 3(NO 3) 6·2MeOH (Ln=GdYb and also Y), Ln 2(EBP) 3 (NO 3) 6· nMeCN (Ln=TbYb), representative members of which have been studied by single crystal X-ray diffraction. Crystals of Eu(EBP) 2(NO 3) 3 are monocline, space group C2/ c, a=20.583(3). b = 9.453(2), c = 17.006(2) A ̊ , β = 120.58(2)°, Z = 4 . The compound is mononuclear with each Eu centre having a coordination environment comprising three chelating nitrates and two nine-membered chelate rings formed by the EBP ligands. Crystals of Tb 2(EBP) 3(NO 3) 6·5MeCN are triclinic, space group PĪ, a = 10.504(5), b = 10.854(4), c = 17.145(6) A ̊ , α = 84.23(2), β = 72.68(2), γ = 72.79(2)°, Z = 2 . The EBP ligands bridge the Tb centres forming sheets of contiguous 54-membered rings. The MeCN molecules of solvation are occluded within the lattice, some lying within the metallamacrocyclic rings and some between the sheets. Crystals of &{[Ho(EBP) 2(MeOH)(NO 3) 3]0.5(EBP)&} 0 are triclinic, space group PĪ, a = 8.316(2), b = 10.138(2), c = 15.441(3) A ̊ , α = 92.82(2), β = 92.29(2), γ = 102.99(2)°, Z = 2 . Each Ho atom is coordinated to three chelating nitrate groups, two bridging EBP ligands and one methanol molecule leading to the formation of polymeric chains [Ho(EBP) 2(MeOH)(NO 3) 3] 0. The remaining EBP molecules are non-coordinated but form hydrogen bonds to the methanol ligands and thereby link adjacent chains to form sheets of contiguous 78-membered rings.