Tripodal 1,3,5-benzenetricarboxamide ligand with dipicolinic acid units and its binding with Eu(III) ions

ABSTRACT The synthesis and characterisation of tripodal ligand 1 containing 1,3,5-benzenetricarboxamide core and diethyl 4-(phenylethynyl)pyridine-2,6-dicarboxylate is described. The crystal structure of the intermediate tripodal molecule 7 exhibits an unusual staggered hydrogen-bonded chain motif instead of the anticipated helical assembly. We studied the basic photophysical properties of 1 in solvents of various polarity including CH3OH, CH3CN, DMSO, and CHCl3. The self-assembly experiments between 1 and Eu(CF3SO3)3⋅6H2O confirmed the formation of metal-ligand self-assembly species in the solution of CH3CN. It was also shown that the excitation of the Eu(III)-centred emission in such species occurred through the energy transfer from the ligand acting as an antenna to the metal centre. The binding constant values were evaluated using the nonlinear regression analysis software SPECFIT®, and their values correspond to those previously observed for the assemblies between 2,6-dipicolinic acid derivatives and lanthanide ions. This work describes the synthesis of tripodal 1,3,5-benzenetricarboxamide ligand with dipicolinic acid units and its binding with Eu(III) ions in solution. The photophysical properties of the target tripodal ligand were studied in solvents of various polarity. The self-assembly experiments between the ligand and Eu(III) ions in solution confirmed the formation of luminescent metal-ligand self-assembly species. Graphical abstract