Solid-state luminescence properties, Hirshfeld surface analysis and DFT calculations of mononuclear lanthanide complexes (Ln = EuIII, GdIII, TbIII, DyIII) containing 4′-phenyl-2,2′:6′,2″-terpyridine

Abstract

Four mononuclear lanthanide complexes containing 4′-phenyl-2,2′:6′,2″-terpyridine (ptpy), [Ln(NO3)3(ptpy)(H2O)] (Ln = Eu (1), Gd (2), Tb (3), Dy (4)), were solvothermally synthesized and characterized via elemental analysis, infrared spectroscopy, thermogravimetric analysis, single-crystal X-ray diffraction, and powder X-ray diffraction. Hirshfeld surfaces and the solid-state luminescence properties of the complexes were investigated. The 3-D Hirshfeld surface and 2-D fingerprint plots show that the main interactions are the O⋯H/H⋯O intermolecular interactions in 1–4. Solid-state luminescence investigation reveals that GdIII complex 2 displays a ligand-centered emission and the EuIII, TbIII and DyIII complexes 1, 3 and 4 show the characteristic lanthanide-centered luminescence upon UV excitations. The EuIII and TbIII complexes exhibit red (CIE: 0.6549, 0.3447) and green (CIE: 0.3760, 0.5412) luminescence in the solid state with quantum yields of 16.8% and 0.8% and lifetimes of 0.545 and 0.043 ms, respectively. Density functional theory (DFT) calculations were conducted to unravel the HOMO–LUMO energy gaps of the structures of ptpy and complexes 1 and 3.