Structures of Silver Pyrazolates in Hydrocarbon Solutions via Vapor-Pressure Osmometry

Abstract

Molecular weights of {[3,5-(CF 3) 2Pz]Ag} 3, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, and {[3,5-( i-Pr) 2Pz]Ag} 3 at various solution concentrations have been investigated using vapor-pressure osmometry. Depending on the concentration, the trinuclear {[3,5-(CF 3) 2Pz]Ag} 3 either dissociates into mono- and dinuclear moieties or remains trinuclear or aggregates to hexanuclear species in toluene. In contrast, {[3-(C 3F 7),5-( t-Bu)Pz]Ag} 3, which has a bulky and relatively electron-rich pyrazolate, retains the trinuclear form even at low concentrations in toluene. Both {[3,5-(CF 3) 2Pz]Ag} 3 and {[3,5-( i-Pr) 2Pz]Ag} 3 adopt trinuclear structures in heptane at low concentrations. At higher concentrations, {[3,5-( i-Pr) 2Pz]Ag} 3 forms hexanuclear species. The aggregation-segregation points are rather sharp and are reminiscent of the all-or-none character of phase transitions. Remarkably, at higher concentrations, the aggregation states of these silver pyrazolates are similar to those expected based on solid-state data.

Silver Pyrazolates as Coordination‐Polymer Luminescent Metallomesogens

“…[26] The MALDI-TOF mass spectra showed several peaks corresponding to fragments with a stoichiometry of [Ag n + 1 pz 3 ] peak, a finding that further supports the polymeric character of the silvercontaining materials. Attempts to characterize the coordination polymers by gel permeation chromatography only gave a signal with a similar retention time to that of the pyrazole ligand.…”

“…In contrast, only one recent work by Dias et al. concerned the reversibility of silver pyrazolates, which behaved as single mono‐, di‐, or polynuclear species in a vapor‐pressure osmometry study on [Ag(μ‐(3,5‐(CF 3 ) 2 pz))] 3 , although the authors did not propose an equilibrium between open‐chain oligomers 26…”

The use of DOSY experiments to determine the solution structures of coinage metal pyrazolates: The case of {[3,5‐(CF3)2Pz]Ag}3

“…One of us has used vapor‐pressure osmometry (VPO) to determine the structure in solution of (12Ag) 3. 43 In heptane they observed only the trimer but in toluene on increasing the concentration (between 2 and 43 mmol·kg −1 , 43 being the limit of solubility) they observed the monomer, the dimer, the trimer and the hexamer (i.e., likely dimer of trimers). It is expected that some of these species (monomers) are stabilized by the solvent coordination.…”

Dinuclear and Trinuclear Complexes of Copper(I) and Silver(I) Supported by a Highly Fluorinated Pyrazolate [3,5‐(CF3)2Pz]– and N‐Heterocycles

“…There is significant current interest in copper(I) and silver(I) pyrazolate complexes due to their diverse structures, cuprophilic and argentophilic d 10 ‐d 10 interactions, π‐acid/π‐base chemistry, and fascinating photo‐physical properties . Homoleptic pyrazolates of these metal ions often adopt trinuclear structures with varying degrees and types of inter‐trimer interactions featuring metallophilic contacts , . For example, {[3,5‐(CF 3 ) 2 Pz]Cu} 3 forms columnar structures of nine‐membered, Cu 3 N 6 rings with somewhat long inter‐trimer Cu ··· Cu contacts (closest at 3.813 Å), while adducts like {[3,5‐( i Pr) 2 Pz]Cu} 3 form strongly interacting dimers of trimers with short Cu ··· Cu (closest at 2.989 Å) contacts .…”

“…An area of research activity in our laboratory concerns the chemistry of copper, silver and gold complexes of highly fluorinated pyrazolates , , , . For example, we have reported convenient routes to the synthesis of trinuclear {[3,5‐(CF 3 ) 2 Pz]M} 3 (M = Cu, Ag, Au) complexes (Figure , 1–3 ), and their remarkable photophysical properties .…”