Trinuclear to dinuclear: A radii dependence lanthanide(III) self-assembly coordination behavior of an amide-type tripodal ligand

摘要

Lanthanide nitrate complexes with the heptadentate ligand L (6-[2-(2-(diethylamino)-2-oxoethoxy)ethyl]-N,N,12-triethyl-11-oxo-3,9-diox a-6,12-diazatetradecanamide), [Ln(2)L(NO3)(6)] (Ln = La, Nd, Sm, Eu, Ho), have been prepared and characterized. The X-ray crystallographic studies show that, in [La2L(NO3)(6)(H2O)].H2O (1), two complex cations [LaL(H2O)](3+) are linked by a hexanitrato anion [La(NO3)(6)](3-) and form a trinuclear cation. In [Nd2L(NO3)(6)(H2O)].CHCl3.1/2CH(3)OH.1/2H(2)O (2), one complex cation [NdL(H2O)](3+) and a hexanitrato complex anion [Nd(NO3)(6)](3-) are linked by a bridging NO3- to form a dinuclear complex. In both complexes, the bridging nitrate is an unusual tetradentate ligand. The metal ions are 12-coordinated in hexanitrato anions and 10-coordinated in complex cations. The chainlike supramolecular structures of La3+ complex are parallel and have no hydrogen bonds in between, while, in the Nd3+ complex, a chiral cavity is formed by hydrogen bonds between two adjacent supramolecular chains. These influences are further investigated by assessing the separation efficiency of L and H-1 NMR spectra of its lanthanide nitrate mixtures in solution. [References: 25]