Syntheses, crystal structures, luminescence properties and Hirshfeld surface analyses of two mononuclear 2,2′:6′,2′’-terpyridine lanthanide complexes with different β-diketones

Six ternary lanthanide complexes with different β-diketones as primary “antenna” ligand and 2,2’:6’,2’’-terpyridine as neutral ancillary ligand, namely [Ln(hfac) 3 (tpy)] [Ln(III) = Eu ( 1 ), Gd ( 2 ), Tb ( 3 ); hfac  =  hexafluoroacetylacetone; tpy = 2,2’:6’,2’’-terpyridine] and [Ln(btfa) 3 (tpy)] [Ln(III) = Eu ( 4 ), Gd ( 5 ), Tb ( 6 ); btfa = 4,4,4-trifluoro-1-phenyl-1,3-butanedione], were synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, single crystal X-ray diffraction and powder X-ray diffraction. The three-dimensional Hirshfeld surface map and two-dimensional fingerprint analysis reveal that the substitution of hfac with btfa result in the decrease of the H···F/F···H and F···F interactions and the increase of the C···H/H···C and H···H interactions. Solid-state luminescence investigations indicate that the Eu(III) complexes ( 1 -Eu and 4 -Eu) and the Tb(III) complexes ( 3 -Tb and 6 -Tb ) display the characteristic lanthanide-centered luminescence upon UV excitations. 1 -Eu and 4 -Eu emit red light at CIE: 0.6827, 0.3172 and CIE: 0.6819, 0.3179 with the quantum yields (QY) of 78.70 % and 68.85 % and the lifetimes ( τ ) of 0.768 and 0.808 ms, respectively. 3-Tb and 6-Tb emit green light at CIE: 0.2677, 0.7221 and CIE: 0.2680, 0.7217 with the QY values of 7.56 % and 1.38 % and the τ values of 0.076 and 0.022 ms, respectively. For the Eu(III) complexes, the substitution of hfac by btfa makes the QY value lower from 78.70 % to 68.85 % and slightly prolong the τ value from 0.768 to 0.808 ms, while for the Tb(III) complexes, both of the QY and τ values decrease. The results suggest that the structures of the primary β-diketone ligands could affect the luminescence performances such as QY and τ values of the Eu(III) and Tb(III) complexes.