Modulating Two Pairs of Chiral Dy^III Enantiomers by Distinct β-Diketone Ligands to Show Giant Differences in Single-Ion Magnet Performance and Nonlinear Optical Response

Abstract

Using Dy(dbm)₃(H₂O) and Dy(btfa)₃(H₂O)₂ to react with enantiopure <i>N</i>-donors, (-)/(+)-4,5-pinenepyridyl-2-pyrazine (L_<i>R</i>/L_<i>S</i>), respectively, two pairs of chiral Dy^III enantiomers, Dy(dbm)₃L_<i>R</i>/Dy(dbm)₃L_<i>S</i> (<b><i>R</i>-1-Dy</b>/<b><i>S</i>-1-Dy</b>) and Dy(btfa)₃L_<i>R</i>/Dy(btfa)₃L_<i>S</i> (<b><i>R</i>-2-Dy</b>/<b><i>S</i>-2-Dy</b>) were obtained, wherein one of the benzene rings of dbm^- (dibenzoylmethanate) in <b><i>R</i>-1-Dy</b>/<b><i>S</i>-1-Dy</b> is displaced by the -CF₃ group of btfa^- (4,4,4-trifluoro-1-phenyl-1,3-butanedionate) in <b><i>R</i>-2-Dy</b>/<b><i>S</i>-2-Dy</b>. Interestingly, this substitution results not only in giant differences in their single-ion magnetic (SIM) performances but also in their completely different nonlinear optical (NLO) responses. <b><i>R</i>-1-Dy</b> presents a large effective energy barrier (<i>U</i>_eff = 265.47 K) under zero applied field, being more than 4 × <b><i>R</i>-2-Dy</b> (61.40 K). The discrepancy on their magnetic performances has been further elucidated by <i>ab initio</i> calculations. Meanwhile, <b><i>R</i>-1-Dy/<i>S</i>-1-Dy</b> display the strongest third-harmonic generation responses (35/33 × α-SiO₂) among the known lanthanide NLO-active coordination compounds (CCs). On the contrary, <b><i>R</i>-2-Dy/<i>S</i>-2-Dy</b> exhibit moderate second-harmonic generation responses (0.65/0.70 × KDP). These results not only give the first example of the CCs with both SMM/SIM behavior and a THG response but also provide an efficient strategy for achieving the function regulation and switch in multifunctional CCs.