2D Near‐Infrared Luminescence Ln–Coordination‐Polymers as an Assistor for Biomedicine

Constructing Near‐Infrared (NIR) lanthanide coordination polymers (Ln‐CPs) is of great importance for biomedicial application, due to low toxicity and high‐resolution transparency of biological tissues. Yb 3+ coordination polymer is researched widely because of its sharp emission at 980 nm could being identified and penetrate tissue easily. In our work, a rigid and highly symmetrical carboxylic acid H 3 L (2,2′‐((5‐carboxy‐1,3‐phenylene)bis(oxy))diacetic acid) was synthesised to build Ln‐CPs. The two‐dimensional (2D) lanthanide coordination polymers (Ln‐CPs)[Ln(L)(Dimethylacetamide)⋅H 2 O]n (Ln=Er, Yb) were obtained by the reaction of Ln(NO 3 ) 3  ⋅ 6H 2 O and H 3 L under 140 °C. Single Crystal X‐ray Diraction (SCXRD) analysis indicates that all the Ln‐CPs present a 2D layer structure formed by lanthanide ions and linkers COO−. The structure of bulk samples were characterized by Powder X‐ray Diffraction (PXRD). The patterns indicate that Yb‐CP and Er‐CP are of excellent phase purity. We also explored the near‐infrared luminescence properties of these coordination polymers at solid‐state. Yb‐CP shows NIR emission at around 980 nm, which can be assigned to the 2 F 5/2 → 2 F 7/2 transition of the Yb 3+ ion.