Synthesis, crystal structure, luminescence, and density functional theory calculation of rare earth complexes based on 1-phenyl-3-methyl-4-benzoyl-5-pyrazolinone

A series of mononuclear rare earth complexes [Ln(pmbp)(3)(dmbipy)]center dot C2H5OH, where Ln=Tb (1-Tb), Ho (1-Ho), Er (1-Er) and Tm (1-Tm), were synthesized by using 1-phenyl-3-methyl-4-benzoyl-5-pyrazolinone (Hpmbp) and 4,4'-dimethyl- 2,2'-bipyridine (dmbipy) as ligands. Structure characterizations show that the complex is composed of one Ln(3+) ion, three pmbp-ions, one dmbipy molecule, and one free ethanol molecule, yielding the [LnO(6)N(2)] type structure. The continuous shape measurement (CShM) analyses show that the Ln(3+) centers exhibit a distorted triangular dodecahedral geometry. Luminescence measurements showed that all of the complexes exhibit characteristic emission peaks of the corresponding rare earth ions. And it was found that the ligand could sensitize Ho3+ and Er3+ well, while the sensitization of Tb3+ and Tm3+ was weak. In addition, the HOMO and LUMO of Hpmbp ligands, dmbipy ligands, and rare earth complexes were calculated and analyzed by the density functional theory method. It is found that for Tb, Ho, and Tm complexes with an odd number of electrons in the center metal atom, the bond lengths between metal ions and coordination atoms are shorter with the increasing number of electrons in metal ions, while the bond lengths of Er-O and Er-N of 1-Er are between those of 1-Ho and 1-Tm. For 1-Tb, 1-Ho, and 1-Tm, the orbital energy of HOMO and LUMO decreases with increasing electron number, which is consistent with the rule of bond length. For 1-Tb, 1-Ho and 1-Er, the HOMO-LUMO gap increases with the increase of electron number. In addition, the HOMO-LUMO energy gaps of the four complexes are lower than that of the ligands. CCDC: 2181993, 1-Tb; 2181994, 1-Ho; 2181995, 1-Er; 2181996, 1-Tm.