Synthesis, Structures, and Luminescence Properties of Lanthanide Complexes with Structurally Related New Tetrapodal Ligands Featuring Salicylamide Pendant Arms

To explore the relationships between the structures of ligands and their complexes, we have synthesized and characterized a series of lanthanide complexes with two structurally related ligands, 1,1,1,1-tetrakis{[(2′-(2-benzylaminoformyl))phenoxyl]methyl}methane (L^I) and 1,1,1,1-tetrakis{[(2′-(2-picolyaminoformyl))phenoxyl]methyl}methane (L^II). A series of zero- to three-dimensional lanthanide coordination complexes have been obtained by changing the substituents on the Pentaerythritol. Our results revealed that, complexes of the L^I ligand, {Ln₄L^I₃(NO₃)₁₂·nC₄H₁₀O}_∞ (Ln = Nd, Eu, Tb, Er, n = 3 or 6)] show the binodal 3,4-connected three-dimensional interpenetration coordination polymers with topology of a (8³)₄(8⁶)₃ notation. Compared to L^I, complexes of L^II present a cage-like homodinuclear [Ln₂L^II₂(NO₃)₆·2H₂O]·nH₂O (Ln = Nd, Tb, Dy, n = 0 or 1) or a helical one-dimensional coordination {[ErL^II(NO₃)₃·H₂O]·H₂O}_∞ polymer. The luminescence properties of the resulting complexes formed with ions used in fluoroimmunoassays (Ln = Eu, Tb) are also studied in detail. It is noteworthy that subtle variation of the terminal group from benzene to pyridine not only sensibly affects the overall molecular structures but also the luminescence properties as well.