Trinuclear Copper(I) and Silver(I) Adducts of 4-Chloro-3,5-bis(trifluoromethyl)pyrazolate and 4-Bromo-3,5-bis(trifluoromethyl)pyrazolate

Syntheses, structural, and photoluminescence properties of {[4-X-3,5-(CF3)(2)Pz]M}(3) (X = Cl or Br, M = Cu or Ag) containing a heavier halide at the pyrazolyl ring 4-positions are reported. The Cu2O and Ag2O react with [4-Cl-3,5-(CF3)(2)Pz]H or [4-Br-3,5-(CF3)(2)Pz]H to form the corresponding metal pyrazolates, which are trinuclear adducts of the type t[4-X-3,5-(CF3)(2)Pz]M}(3) with a nine-membered M3N6 metallacyclic core. They also feature relatively short M center dot center dot center dot Cl or M center dot center dot center dot Br intertrimer separations (similar to 3.6 angstrom) leading to supramolecular aggregates in the solid state. Distinct from the 4-H analogues {[3,5-(CF3)(2)Pz]M}(3), none of the four complexes described herein exhibits short intertrimer metal-metal interactions (as closest such M center dot center dot center dot M separations are at a distance greater than 5.0 angstrom). The {[4-X-3,5-(CF3)(2)Pz]M}(3) adducts exhibit bright photoluminescence even at room temperature. The photophysical data suggest that the {[4-X-3,5-(CF3)(2)Pz]Cu}(3) complexes emit from an associative excited state, and the drastic Stokes shift suggests a significant change to the ground state structure of the trinuclear moiety and/or intermolecular interactions upon photoexcitation. The {[4-X-3,5-(CF3)(2)Pz]Ag}(3) complexes emit from a ligand-centered excited state affected by silver and the heavier halogens. Thin films of {[4-X-3,5-(CF3)(2)Pz]Cu}(3) trimers are promising for volatile organic compound (VOC) sensor applications as they exhibit luminescence color change upon exposure to vapors of benzene and its alkylated derivatives.