Solid-state luminescence properties, Hirshfeld surface analysis and DFT calculations of mononuclear lanthanide complexes (Ln = Eu, Gd, Tb, Dy) containing 4'-phenyl-2,2':6',2″-terpyridine.

Four mononuclear lanthanide complexes containing 4'-phenyl-2,2':6',2″-terpyridine (ptpy), [Ln(NO)(ptpy) (HO)] (Ln = Eu (), Gd (), Tb (), Dy ()), 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 -. Solid-state luminescence investigation reveals that Gd complex displays a ligand-centered emission and the Eu, Tb and Dy complexes , and show the characteristic lanthanide-centered luminescence upon UV excitations. The Eu and Tb 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 and .