Crystalline Phase Induction Strategy for the Design of Luminescent Lanthanide Coordination Polymers: Toward Plastic...

Reactions in water between a lanthanide chloride and the disodium salt of tetrachloro-phthalate (tcpa^2-) lead to a family of isostructural coordination polymers with the general chemical formula [Ln₂(tcpa)₃(H₂O)₄]_∞ with Ln = La-Pr (Family 2, F2). The crystal structure was solved based on the La-derivative. It crystallizes in the monoclinic system, space group P2₁/n (n°14) with the following cell parameters: a = 6.2491(3) Å, b = 17.5805(6) Å, c = 32.1537(14) Å, β = 90.098(2)°, V = 3532.5(3) ų, and Z = 4. However, this series does not host coordination polymers based on lanthanides that are luminescent in the visible region. These lanthanide ions lead to compounds that crystallize in a previously reported structural family with the general chemical formula [Ln₂(tcpa)₃(H₂O)₆]_∞ with Ln = Eu-Lu (Family 1, F1). Accordingly, we used a "phase induction strategy" to force Tb³⁺-, Eu³⁺-, and Sm³⁺ -containing molecular alloys to crystallize in F2, and we demonstrate that luminance was optimized when compared with those of F1 despite similar intermetallic energy transfers. This observation was rationalized by theoretical calculations that suggest that the greater rigidity of the crystal structure F2 could be responsible for this notable difference in the luminescence properties.