Structural and selectivity of 18-crown-6 ligand in lanthanide–picrate complexes

摘要: Abstract The selectivity factor in the separation of lanthanide could be associated with coordination behaviour. Thus, we observed study solid phase to understand pattern Ln(III) 18-crown-6 (18C6) ligand. Good rigid 18C6 ligand toward depends on gradually smaller their ionic radii complexes formation presence picrate anion (Pic−), i.e. contraction and steric effects as clearly shown series [Ln(Pic)2(18C6)]+(Pic)− {Ln = La, Ce, Pr, Nd, Sm, Gd} [Ln(Pic)3(OH2)3] · 2(18C6) · 4H2O {Ln = Tb, Ho} complexes. La–Gd crystallized an orthorhombic space group Pbca, while Ho complex triclinic P 1 ¯ . lighter lanthanides [La–Sm] had a 10-coordination number from two picrates, forming bicapped square-antiprismatic geometry. Meanwhile, middle [Gd] nine-coordination tricapped trigonal prismatic heavier [Ho] is rather unique, since Ho(III) coordinated nine oxygen atoms three picrates water molecules opposite direction whereas surrounded inner sphere, effective controlling molecular geometry bonding Ln–O can use crystal engineering approach. No dissociation bonds solution was NMR studies conducted at different temperatures. photoluminescence spectrum Pr has typical 4f–4f emission transitions, 3P0 → 3F2 (650 nm), 1D2 → 3F2 (830 nm) 1D2 → 3F4 (950 nm).