Abstract
Creating optically pure metal assemblies is a hot research topic in the realms of chiral supramolecules. Here, three new triple-stranded europium(iii) helicates Eu(2)L(3)(L')(2) [L = 4,4'-bis(4,4,4-trifluoro-1,3-dioxobutyl)diphenyl sulphide; L' = 1,10-phenanthroline (Phen) or R/S-2,2'-bis(diphenylphosphinyl)-1,1'-binaphthyl (R/S-BINAPO)] were synthesized in order to investigate the effects of ancillary ligands on controlling the stereoselective self-assembly of lanthanide helicates. X-ray single crystal structure analysis showed that Eu(2)L(3)(Phen)(2) crystalized in an achiral space group P1̄ with the equivalent amount of P and M helicates in one single cell. The isolated Eu(2)L(3)(S-BINAPO)(2) and Eu(2)L(3)(R-BINAPO)(2) were verified to be enantiopure by (1)H, (19)F, (31)P NMR and DOSY NMR analyses. Additionally, the mirror-image CD spectra also demonstrated the successful syntheses of the enantiomers and the presence of an effective chirality transformation from BINAPO to achiral L. Furthermore, the perfect mirror-image circularly polarized luminescence (CPL) spectra of Eu(2)L(3)(S-BINAPO)(2) and Eu(2)L(3)(R-BINAPO)(2) indicated the existence of the excited state chirality of the Eu(3+) center associated with |g (lum)| values reaching 0.112. In addition, the photophysical properties of three helicates were also discussed.