A small-molecular europium complex with anion sensing sensitivityElectronic supplementary information (ESI) available. CCDC reference number 891974. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c2dt31607b

• Main Authors: Wang, Jianwei, Wu, Jiang, Chen, Yanmei, Wang, Haiping, Li, Yiran, Liu, Weisheng, Tian, Hao, Zhang, Ting, Xu, Jun, Tang, Yu
• Format: Article
• Language: English
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/c2dt31607b

A novel small-molecular europium( iii ) complex with quinoline derivative has been designed and prepared for anion recognition. This Eu 3+ complex displays striking emission changes at 616 nm in response to NO 3 − and Cl − . What's more, the anion-selective luminescence enhancement is easily detected by the naked eye. UV, luminescence titration experiments and the Job plot analysis revealed that the ligand can form stable 1 : 1 complexes with Eu(NO 3 ) 3 or EuCl 3 in CH 3 CN; log K = 7.10 and 6.76 (295 K), respectively. The crystal structure shows that three oxygen atoms and one nitrogen atom of the ligand are approximately coplanar and wrap around the Eu 3+ ion through a semicircle-shaped coordination structure and some unoccupied sites of the central europium ions are available for guest anions in the complexes. Thus, three nitrate ions are located in the gap of the semicircle. It is supposed that the mechanism of luminescence enhancement is of NO 3 − or Cl − anions squeezing out solvent molecules from the inner coordination sphere. A novel europium complex was designed and synthesized for recognizing NO 3 − and Cl − which may squeeze out the coordinated solvent molecules to enhance the luminescence.