A series of mononuclear lanthanide complexes featuring 3-D supramolecular networks: synthesis, characterization and luminescent properties for sensing guest molecules

Abstract

A new series of four isostructural mononuclear lanthanide complexes Ln(HPDH)₃(H₂O)₃·H₂O (Ln = Sm(III) 1, Eu(III) 2, Tb(III) 3 and Dy(III) 4; H₂PDH = 6,7-dihydropyrido(2,3-d)pyridazine-5,8-dione) has been prepared and characterized by IR, elemental analysis, XRD and TG-DTA methods. Single crystal X-ray diffraction analysis of both complexes 1 and 3 revealed that the mononuclear discrete complexes form 3-D supramolecular networks via hydrogen bonds and offset stacking (–H⋯π) interactions. The photoluminescence study of the title complexes revealed the photoluminescent potential of the antenna ligand (H₂PDH) toward the concerned lanthanide cations. The luminescence based sensing ability of the partially dehydrated complex Tb(HPDH)₃(H₂O)₃3a towards small solvent molecules, along with its reusability, has been studied. Isopropyl alcohol was found to be an excellent sensitizer, while tetrahydrofuran was a highly quenching solvent with a first order behavior towards the photoluminescence intensity. The photoluminescence intensity was found to decrease with the increase of the dielectric constant and normalized Dimroth–Reichardt E_T parameter values for protic solvents, while reverse behavior was observed for dipolar aprotic solvents.