The role of structure and the metal ion in the fluorescence sensing of nitro compounds for a series of lanthanide(iii) 9,10-anthracene dicarboxylate coordination polymers

Abstract

Twenty-eight lanthanide coordination polymers (CPs) containing 9,10-anthracene dicarboxylate (ADC) linkers have been synthesized and characterized. For the earlier class of lanthanides La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Eu³⁺, Gd³⁺ and Tb³⁺, the 3D pcu net was generated from dimethylformamide (DMF) while a 2D hcb net was formed using dimethylacetamide (DMA). Similarly for the later class of lanthanides, Dy³⁺, Ho³⁺, Er³⁺, Tm³⁺, Yb³⁺ and Lu³⁺, a 2D hcb net was formed when dimethylacetamide (DMA) was used. However, the formation of a crystalline product with DMF was possible only when DMSO was added together for these lanthanides, and they yielded 2D structures despite the usage of DMF. Only the single crystal structures of Er³⁺ and Ho³⁺ have been determined and the rest of the structures were confirmed by PXRD studies. These compounds have been used to sense various nitro compounds. In particular, they are the most sensitive to Brady's reagent, 2,4-dinitrohydrazobenzene. There was no difference in the quenching extent between the 3D and 2D early lanthanide CPs. For the later lanthanides which adopt 2D structures, the quenching efficiency is higher when DMA instead of DMSO is coordinated suggesting the solvent effect in emission quenching.