Novel Configurational Structures of Sodium Tetrakis(3-heptafluorobutylryl-(+)-camphorato) Ln(III) Complexes with a Trapped Na⁺ by Na⁺···FC Interactions in the Solid State and in Solution

Abstract

For newly prepared sodium tetrakis(3-heptafluorobutylryl-(+)-camphorato) Ln(III) complexes, the X-ray crystal analysis revealed an unprecedented pseudo-achiral dodecahedron (DD-8 (D(2d))), whereas in CHCl3 solution, the exciton CD and 19F NMR spectra showed a novel chiral Delta-SAPR-8 (C4) configuration which is stereospecifically formed by a trapped Na+ ion with Na+...FC (fluorocarbon) interactions.

Stereochemistry and solid-state circular dichroism spectroscopy of eight-coordinate chiral lanthanide complexes

“…Up to now, such research has been just focused on 4-to 9-coordinate complexes [2][3][4][5][6][7][8][9][10][11][12][13] , and this doesn't match well with the extensive attentions to the structures and applications for 7-to 12-coordinate lanthanide complexes. In relation to the kinetic liability of most lanthanide complexes, investigation of their chiral-at-metal configurations and kinetic stability basing on the spectra-absolute configuration correlation methods is of great importance to elucidation of diagnosis and treatment mechanisms of chirality discrimination and chirality sensing in life science [4,[10][11][12][13] . Therefore, how to determine the absolute configurations of chiral complexes with higher coordination number (CN) remains to be a challenge in polyhedral stereochemistry of chiral lanthanide complexes.…”

“…In the above-mentioned examples, Kaizaki [4,6,9] and Parker et al [12] made full use of different chromophores in the eight-coordinate complexes and then made rational selection of special regions for the solution CD measurements. For example, both the exciton splitting (insensitive to metal types) [1,4] arising from the π-π* transition of β-diketones in the UV region and the Cotton effects (sensitive to metal types) [9] originated from the f-f chromophores in the vis-NIR region are useful in investigating the absolute configurations of chiral β-diketone lanthanide complexes.…”

“…For example, both the exciton splitting (insensitive to metal types) [1,4] arising from the π-π* transition of β-diketones in the UV region and the Cotton effects (sensitive to metal types) [9] originated from the f-f chromophores in the vis-NIR region are useful in investigating the absolute configurations of chiral β-diketone lanthanide complexes. In addition, in the SAP structured Eu or Tb complexes with very low symmetry, the metal-centered chirality is homology with the f-f chromophores, resulting in large dissymmetry factors (g = Δε ext /ε max ) and enhancement of the f-f transition CD signals in the visible range which should be very weak under high symmetry of the coordination sphere around lanthanide ions.…”

Absolute Chiral Structures of Inorganic Compounds

“…78 Also, chiral tetrakis chelate complexes with four 3-heptafluorobutyryl-( þ )-camphorates (( þ )-hfbc), Na[Ln(( þ )-hfbc) 4 ] Á CH 3 CN, takes D-SAPR-8 configuration. 79,80 This complex is stabilized by interaction of the fluorocarbon moiety with the Na ion in CHCl 3 . The structure was determined on the basis of the exciton CD (see below), although the X-ray structure analysis showed only one pseudo-enantiomer with "pseudo-achiral D 2d configuration."…”

“…The structure was determined on the basis of the exciton CD (see below), although the X-ray structure analysis showed only one pseudo-enantiomer with "pseudo-achiral D 2d configuration." 79,80 There have also been a number of compounds formed with tetra-azo-cyclododecane-based ligands such as the tetraphosphinate complex shown in Figure 5.23. These complexes have approximate C 4 symmetry.…”