Lanthanide-Based Coordination Polymers Assembled by a Flexible Multidentate Linker: Design, Structure, Photophysical Properties, and Dynamic Solid-State Behavior

Four picolinate building blocks were implemented into the multidentate linker N,N',N'-tetrakis[(6-carboxypyridin-2-yl)methyl]butylenediamine (H(4)tpabn) with a linear flexible spacer to promote the assembly of lanthanide-based ID coordination polymers. The role of the linker in directing the geometry of the final assembly is evidenced by the different results obtained in the presence of Htpab(n)(3-) and tpabn(4-) ions. The tpabn(4-) ion leads to the desired 1D polymer {[Nd-(tpabn)]H3O center dot 6H(2)O}(infinity) (12). The Htpabn(3-) ion leads to the assembly of Tb-III and Er-III ions into 1D zigzag chains of the general formula {[M-(Htpabn)]center dot xH(2)O}(infinity) (M=Tb, x=14 (1); M=Tb, x=8 (11); M=Er, x=14 (2) M=Er, x=5.5 (4)), a 2D network is formed by the Eu-III ion (i.e., {[Eu-(Htpabn)]-10H(2)O)(infinity) (7)}, and both supramolecular isomers (ID and 213) are obtained by the Tb-III ion. The high flexibility of the polymeric chains results in a dynamic behavior with a solvent-induced reversible structural transition. The Tb-III- and Eu-III-containing polymers display high-luminescence quantum yields (38 and 18%, respectively). A sizeable near-IR luminescence emission is observed for the Er-III and Nd-III-containing polymers when lattice water molecules are removed.