Silver(I) Coordination Polymer Ligated by Bipyrazole Me4bpzH2, [Ag(X)(Me4bpzH2)] (X = CF3CO2- and CF3SO3-, Me4bpzH2 = 3,3',5,5'-Tetramethyl-4,4'-bipyrazole): Anion Dependent Structures and Photoluminescence Properties

Kiyoshi Fujisawa; Yui Kobayashi; Mitsuki Okano; Ryota Iwabuchi; Shiori Kondo; David James Young

doi:10.3390/molecules28072936

Silver(I) Coordination Polymer Ligated by Bipyrazole Me₄bpzH₂, [Ag(X)(Me₄bpzH₂)] (X = CF₃CO₂^- and CF₃SO₃^-, Me₄bpzH₂ = 3,3',5,5'-Tetramethyl-4,4'-bipyrazole): Anion Dependent Structures and Photoluminescence Properties

Molecules. 2023 Mar 24;28(7):2936. doi: 10.3390/molecules28072936.

Authors

Kiyoshi Fujisawa¹, Yui Kobayashi¹, Mitsuki Okano¹, Ryota Iwabuchi¹, Shiori Kondo¹, David James Young²

Affiliations

¹ Department of Chemistry, Ibaraki University, Mito 310-8512, Ibaraki, Japan.
² Faculty of Science and Technology, Charles Darwin University, Darwin, NT 0909, Australia.

Abstract

Coordination polymers of transition metal ions are fascinating and important to coordination chemistry. One of the ligands known to form particularly interesting coordination polymers is 3,3',5,5'-tetramethyl-4,4'-bipyrazole (Me₄bpzH₂). Group 11 metal(I) ion coordination polymers, other than those of copper(I), are relatively easy to handle because of their low reactivity towards dioxygen and moisture. However, the known silver(I) coordination polymers often have poor solubility in common solvents and so cannot be easily analyzed in solution. By using a tetramethyl substituted bipyrazole ligand, we have synthesized more soluble silver(I) complexes that contain the trifluoromethyl group in the coordinated ions CF₃CO₂^- and CF₃SO₃^- in [Ag(CF₃CO₂)(Me₄bpzH₂)] and [Ag(CF₃SO₃)(Me₄bpzH₂)]. We determined both structures by single-crystal X-ray analysis at low temperatures and compared them in detail. Moreover, we investigated the solution behavior of these coordination polymers by ¹H-NMR, IR, Raman, UV-Vis spectroscopies, and their low-temperature, solid-state photoluminescence. The high-energy band at ~330 nm corresponded to ligand-centered (bipyrazole) fluorescence, and the low-energy band at ~400 nm to ligand-centered phosphorescence resulting from the heavy atom effect.

Keywords: bipyrazole ligand; coordination polymer; crystal structure; photoluminescence; silver.

Grants and funding

This research was funded by an Ibaraki University Priority Research Grant and the Joint Usage/Research Center for Catalysis. (Proposal 22DS0143 and 23DS0198).