²_∞[Bi₂Cl₆(pyz)₄]: A 2D-Pyrazine Coordination Polymer As Soft Host Lattice for the Luminescence of the Lanthanide Ions Sm³⁺, Eu³⁺, Tb³⁺, and Dy³⁺

The 2D-coordination polymer 2∞[Bi2Cl6(pyz)4] was synthesized from BiCl3 and a self-consuming melt of pyrazine (pyz). It proves to be a suitable soft host lattice for in situ co-doping of the lanthanide ions Sm3+, Eu3+, Tb3+, and Dy3+ during network formation. The series of luminescent networks 2∞[Bi(2–x)LnxCl6(pyz)4] obtained exhibits an efficient antenna effect on the lanthanide ions. Emission is almost exclusively observed from the lanthanide centers at room temperature, whereas cooling to 77 K reveals a bismuth–pyrazine metal-to-ligand charge transfer related phosphorescence, which is also present without lanthanide participation. All parts of the coordination polymer can function for light uptake. Partial substitution is achieved by statistic replacement of bismuth with lanthanides and can range up to 25 at. % for trivalent europium.