Polymeric CuX coordination compounds assembled from acetylenic thioether ligands RSCH2CCCH2R (R = C6H11, t-Bu): effect of the RS-group, halide and stoichiometry on the network architecture and the luminescence properties

Abstract

A series of coordination polymers (CPs), some of them featuring an unusual architecture, have been constructed by treatment of RSCH₂CCCH₂SR (R = C₆H₁₁L1, t-Bu L2) with CuX (X = Cl, Br, I) and CuX₂. The outcome of the reaction of L1 with CuI depends on the metal-to-ligand ratio. Treatment of CuI with L1 in a 2 : 1 ratio affords the luminescent 2D CP [Cu₄I₄(μ-L1)₂]_n (CP1), whose grid-shaped network is built upon Cu₄(μ₃-I)₄ cubane-like clusters as secondary building units (SBUs), interconnected via bridging L1 ligands. The use of a 1 : 1 ratio gives a material, whose particularity is the coexistence of two topological isomers within the unit cell. The first one, [{Cu(μ₂-I)₂Cu}(μ-L1)₂]_n (CP2), consists of 1D ribbons. The second isomer having a 0D topology, [{Cu(μ₂-I)₂Cu}(μ-L1)₂] D1, is built upon discrete molecular complexes, whose dinuclear [Cu(μ₂-I)₂Cu] rhomboid-shaped core is spanned by two bridging L1 ligands. Mixing CuBr with L1 in MeCN solution leads to an isostructural material incorporating both 0D [{Cu(μ₂-Br)₂Cu}(μ-L1)₂] complex D2 along with the 1D isomer [{Cu(μ₂-Br)₂Cu}(μ-L1)₂]_n (CP3). However, only the 1D CP [{Cu(μ₂-Cl)₂Cu}(μ-L1)₂]_n (CP4) results from complexation of L1 with CuCl. A stoichiometry-dependence is also noticed upon treatment of CuI with L2. Conducting the reaction in a 2 : 1 ratio yields the luminescent 2D CP [Cu₄I₄(μ-L2)₂]_n (CP5), whereas mixing equimolar amounts of the reactants produces 2D CP [{Cu(μ₂-I)₂Cu}(μ-L2)₂]_n (CP6). Structurally similar 2D CPs [{Cu(μ₂-X)₂Cu}(μ-L2)₂]_n (CP8 and CP9) result from complexation of L2 on CuBr or CuCl, respectively. Treatment of L2 with an excess of CuBr or CuBr₂ in refluxing acetonitrile led to the transfer of Br to the acetylenic triple bond, generating an olefinic halogenated dithioether ligand Bu L3 that coordinates to CuBr to generate a 1D network [{Cu(μ₂-Br)₂Cu}(CH₃CN)(μ-L3)]_n (CP9). Using different conditions (propionitrile at 293 K), the reaction of L2 and excess CuBr led to the formation of a 2D network [{Cu(μ₂-Br)₂Cu}(μ-L2)(μ-L3)]_n (CP10) incorporating both L2 and L3 in an alternating manner as assembling ligands. An isostructural chloro-analogue 2D [{Cu(μ₂-Cl)₂Cu}(μ-L2)(μ-L4)]_n (CP11) was obtained using CuCl or CuCl₂. The crystallographic work is completed by thermal analyses and investigation of the luminescence properties of CP1 and CP5 at 77 and 298 K.