Structural Systematics for Lanthanide(III) Systems: Lattice Interactions in Salts [CoL3][Ln(dipic)3]·nH2O (L = N,N′‐Aromatic Bidentate Ligand; dipic = Dipicolinate = pyridine‐2,6‐dicarboxylate) Containing Complex Ions of D3 Symmetry

Structural characterisation of a number of hydrated solids containing chiral, kinetically inert [Co(A–A)₃]³⁺ cations (A–A = 2,2′‐bipyridine, 1,10‐phenanthroline, 4,4′‐dimethyl‐2,2′‐bipyridine) and chiral, kinetically labile [Ln(dipic)₃]^3– anions (Ln = La, Eu, Tb, Ho, Er, Lu, Y, though not for all cobalt cations; dipic = dipicolinate = pyridine‐2,6‐dicarboxylate) show a remarkable range of associations between the lattice components, though all are racemic arrays. Analysis of the structures in terms of short interatomic contacts between the components shows that, whereas numerous contacts of the heteroaromatic ligands do occur, very few define an arrangement which could be truly termed “π‐stacking” where the rings are closely parallel and atom overlaps in projection are substantial. Water is important in the highly hydrated lattice structures, not only because of hydrogen‐bonding interactions with itself and carboxylate‐O atoms but also because of its interactions with the aromatic units. The family [Co(bipy)₃][Ln(dipic)₃]·~13H₂O are essentially isomorphous for the full range of Ln plus Y (triclinic, Pbar{1} , a = 12.3, b = 14.3, c = 16.5 Å, α = 94, β = 94, γ = 108 ?, Z = 2). Among the heavier lanthanides, the potential symmetry of the anion/cation combination is realised in the trigonal space group Pbar{3} , both species lying together as an ion‐pair, disposed on the trigonal axis for [Co(phen)₃][Ln(dipic)₃]·22H₂O (Ln = Eu, Er; a = 15.2, c = 16.8 Å, Z = 2).