Construction of two lanthanide complexes based on N- and O-donors: synthesis, luminescence, and biological activities

Abstract

Two new isostructural dinuclear complexes, Ln₂(4-cpa)₆(phen)₂ (Ln = Eu (1); Tb (2), 4-cpa^– = 4-chlorophenylacetate, phen = 1,10-phenanthroline), have been hydrothermally synthesized and characterized by IR spectroscopy, elemental analysis, thermogravimetric analysis, powder X-ray diffraction, and single-crystal X-ray diffraction. The lanthanides are bridged by two bidentate and two tridentate carboxylato groups to give centrosymmetric dimers with Ln···Ln separations of 3.967(2) and 3.937(3) Å for 1 and 2, respectively. Each metal is nine-coordinate and exhibits a distorted tricapped trigonal prismatic geometry. Both 1 and 2 emit characteristic, intense luminescence at room temperature with lifetimes up to 0.890 ms (at 611 nm) and 0.995 ms (at 543 nm). Poor luminescence efficiency is observed for 2. 4-Chlorophenylacetate, 1 and 2 have been screened for their phytogrowth-inhibitory activities against Brassica napus L. and Echinochloa crusgalli L., and the results are compared with the activity of quizalofop-P-ethyl.

Graphical Abstract

Keywords:

• Lanthanide complexes
• Hydrothermal synthesis
• Crystal structures
• Luminescent properties
• Biological activities

Funding

This work was partially supported by Natural Science Research Foundation of Zhaoqing University, China [grant number 201003]; Educational Research Foundation of Zhaoqing University, China [grant number JY201154]; Foundation for Distinguished Young Talents in Higher Education of Guangdong Province [grant number 2012LYM_0134]; Science and Technology Planning Project of Zhaoqing City [grant number 2012G013]; China Natural Science Fund [grant number 81202461]; and the China Postdoctoral Science Foundation [grant number 2013M531906].