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

Flexible director: A flexible multidentate linker containing picolinate chromophores directs the selective formation of luminescent 1D lanthanide‐based polymers. Partial protonation significantly decreases the preorganization of the linker, thus leading to supramolecular 1D and 2D isomers (see scheme). The lanthanide‐containing 1D polymers undergo reversible structural modification in the hydration/dehydration process, which is also associated with significant differences in the luminescence emission. magnified image Four picolinate building blocks were implemented into the multidentate linker N,N′,N′‐tetrakis[(6‐carboxypyridin‐2‐yl)methyl]butylenediamine (H4tpabn) with a linear flexible spacer to promote the assembly of lanthanide‐based 1D 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 Htpabn3− and tpabn4− ions. The tpabn4− ion leads to the desired 1D polymer {[Nd(tpabn)]H3O⋅6 H2O}∞ (12). The Htpabn3− ion leads to the assembly of TbIII and ErIII ions into 1D zigzag chains of the general formula {[M(Htpabn)]⋅x H2O}∞ (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 EuIII ion (i.e., {[Eu(Htpabn)]⋅10 H2O}∞ (7)), and both supramolecular isomers (1D and 2D) are obtained by the TbIII ion. The high flexibility of the polymeric chains results in a dynamic behavior with a solvent‐induced reversible structural transition. The TbIII‐ and EuIII‐containing polymers display high‐luminescence quantum yields (38 and 18 %, respectively). A sizeable near‐IR luminescence emission is observed for the ErIII‐ and NdIII‐containing polymers when lattice water molecules are removed.