Structural characterization and excited-state properties of luminescent Tris-(? -3-methyl-5- trifluoromethylpyrazolato)trigold(I)

Abstract

Tris-(μ-(3-methyl-5-trifluoromethylpyrazolato)-κN:κN′)triangulo-trigold(I), (3,5-tfmpz)3 Au3, has been synthesized and exhibits a planar nine-member ring containing a central gold triangle with an average intramolecular Au–Au distance of 3.3455(8) A. The complex crystallizes in the monoclinic space group Cc with a = 12.998(2) A, b = 22.910 (3) A, c = 7.217(1) A, and β = 104.781(1)∘. The solid-state structure consists of sheets of (3,5-tfmpz)3Au3 units stacked in an “offset” fashion along the c axis such that one gold atom in each Au3 unit (Au1) lies approximately over the midpoint of the Au1–Au3 edge of the triangle in the layer below it. The intermolecular Au–Au distances are between 3.880(1) and 4.023(1) A, which are too long for there to be significant intertrimer bonding interaction suggesting that any supramolecular organization may be due to hydrogen-fluorine and fluorine-fluorine interactions between the molecules. The complex exhibits excitation-dependent emission at room temperature in the solid state. The structured higher energy emission (λem = 468, 517, and 556(sh) nm) is believed to be a ligand-centered π → π* transition with a lower energy unstructured emission (λem = 658 nm) assigned to the classical Au–Au excited state transition.