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

Abstract

<p>Two new isostructural dinuclear complexes, Ln₂(4-cpa)₆(phen)₂ (Ln = Eu (<b>1</b>); Tb (<b>2</b>), 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 <b>1</b> and <b>2</b>, respectively. Each metal is nine-coordinate and exhibits a distorted tricapped trigonal prismatic geometry. Both <b>1</b> and <b>2</b> 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 <b>2</b>. 4-Chlorophenylacetate, <b>1</b> and <b>2</b> have been screened for their phytogrowth-inhibitory activities against <i>Brassica napus</i> L. and <i>Echinochloa crusgalli</i> L., and the results are compared with the activity of quizalofop-P-ethyl.</p