Exploring supramolecular assembly and luminescent behavior in a series of RE-p-chlorobenzoic acid-1,10-phenanthroline complexes

Eleven new rare earth (RE) p-chlorobenzoic acid-1,10-phenanthroline complexes have been hydrothermally synthesized and structurally characterized via single-crystal and powder X-ray diffraction. This series builds on four previous single complex studies to analyze the structural, supramolecular and luminescent properties of the set of binuclear molecular complexes that are formed with all members of the lanthanide series and yttrium (La-Y). All complexes discussed herein feature a bidentate phenanthroline ligand, p-chlorobenzoic acid ligands exhibiting multiple bind modes, chelating-bridging bidentate, bridging bidentate, bidentate and monodentate, and for the larger Ln(3+) ions (La-Nd) a bound water molecule. Supramolecular assembly yields 2D sheets for all the binuclear species with Cl-pi, pi-pi and hydrogen bonding interactions simultaneously present in structure type I, pi-pi and hydrogen bonding assembling the binuclear tectons in structure type II and a combination of Cl-pi and pi-pi interactions stitching together the dimer units of structure type III. Visible luminescence experiments were performed on the Pr, Sm, Dy and Tm materials and the results ranged from complete sensitization for Sm and Dy to incomplete energy transfer in the Tm complex, and a complete absence of luminescence in the Pr material.