Synthesis, supramolecular isomerism, and photoluminescence of scandium(III) complexes with a tetrafluoroterephthalate ligand.

Here we present a new family of seven Sc(III) complexes with a tetrafluoroterephthalate ligand (tFBDC²⁻), having non-polymeric and polymeric 2D and 3D structures. These complexes are characterized by SC XRD, PXRD, FT-IR, elemental analysis, and TGA. Among these complexes, 3D coordination polymers [Sc(H₂O)(tFBDC)_1.5]·H₂O (1), [Sc₂(H₂O)₂(tFBDC)₃]·2H₂O (2), and [Sc(H₂O)(tFBDC)_1.5]·4H₂O (3) are supramolecular isomers. Complex 1 is obtained as a phase pure material, while 2 and 3 are found as admixtures. The reaction of Sc(CF₃SO₃)₃ with H₂tFBDC in the presence of NH₃ as a base produces layered coordination polymer [Sc(H₂O)(OH)(tFBDC)] (4). Complexes (NH₄)[Sc(H₂O)₄(tFBDC)₂]·5H₂O (5), [K(H₂O)₂Sc(H₂O)₄(tFBDC)₂]·3H₂O (6) and [Cs(H₂O)₄Sc(H₂O)₄(tFBDC)₂]·0.5H₂O (7) based on the same [Sc(H₂O)₄(tFBDC)₂]⁻ anionic unit are obtained by precipitation with NH₃, KOH or CsOH. Coordination polymers 1 and 4 are stable in an aqueous solution in the range of pH 2–12. Solid complexes 1, 4–7 show ligand-centred purple/blue photoluminescence, with 1 and 4 having high quantum yields of 28 and 34% at room temperature. [ABSTRACT FROM AUTHOR]