Two pairs of chiral Yb^III enantiomers presenting distinct NIR luminescence and circularly polarized luminescence performances with giant differences in second-harmonic generation responses

By introducing enantiomerically pure mono-bidentate N-donor ligands (L-R/L-S) into Yb(btfa)(3)(H2O)(2) and Yb(dbm)(3)(H2O), respectively, two pairs of chiral Yb-III enantiomers, namely Yb(btfa)(3)L-R/Yb(btfa)(3)L-S (D-1/L-1) and [Yb(dbm)(3)L-R][Yb(dbm)(3)(C2H5OH)]/[Yb(dbm)(3)L-S][Yb(dbm)(3)(C2H5OH)] (D-2/L-2) were isolated, where btfa(-) = 3-benzoyl-1,1,1-trifluoroacetonate, dbm(-) = dibenzoylmethanate, and L-R/L-S = (-)/(+)-4,5-pinenepyridyl-2-pyrazine. D-1/L-1 possess mononuclear structures in which the Yb-III ions are eight-coordinated, while D-2/L-2 show cocrystal structures containing Yb(dbm)(3)(L-R/L-S) and Yb(dbm)(3)(C2H5OH) moieties in which the two Yb-III ions are eight and seven-coordinated, respectively. They not only feature different molecular structures but also present distinct linear and nonlinear optical performances. Chiral mononuclear D-1 has better near infrared photo-luminescence (NIR-PL) and circularly polarized luminescence (CPL) performances than chiral cocrystal D-2. More remarkably, D-1/L-1 show large second-harmonic generation (SHG) responses (up to 1.25/1.28 x KDP) 18/16 times those of D-2/L-2 (0.07/0.08 x KDP). In addition, D-2/L-2 represent the first examples of lanthanide cocrystal complexes with NIR-PL, NIR-CPL and SHG properties.