Lanthanide Coordination Polymers with Soft-Base Ditopic Bisthiazolate Ligands.

In order to prepare the first lanthanide coordination polymers (CPs) based on ditopic sulfide ligands, benzo[1,2-:4,5-']bisthiazole-2,6(3,7)-dithione (HL) was used as a linker. The reactions of lanthanide silylamides Ln[N(SiMe)] (Ln = Nd, Gd, Er, and Yb) with HL result in the formation of soluble dimethyl sulfoxide (DMSO) ionic salts [Ln(DMSO)][L] [Ln = Nd (), Gd (), Er (), and Yb ()]. Due to the lack of coordination of anionic ligands, compounds , , and do not show sensitized metal-centered photoluminescence (PL), while Gd compound shows weak phosphorescence at 77 K. It was found that the heating of in a 1:9 DMSO/1,4-dioxane mixture leads to the formation of large crystals of 2D CP [Nd(DMSO)L·0.5diox] (), where deprotonated dithione HL plays the role of a ditopic linker. This linker acts as an "antenna" in compound , providing an intense near-infrared (NIR) PL of Nd ion upon near-UV and blue-light excitation. The application of a synthetic protocol similar to that of compounds - led to the formation of amorphous compounds [Ln(DMSO)L·0.5diox] [Ln = Gd (), Er (), and Yb ()], whose PL properties significantly differ from those of the parental ionic salts. In the case of Yb polymer , the PL excitation spectra are shifted to the red region due to a low-energy ligand-to-metal charge-transfer state. The synthesized compounds - are the first examples of lanthanide CPs using soft-base ditopic linkers in their structures.