Four new Cu I /Ag I -based coordination compounds containing 2-mercapto-5-methyl-1,3,4-thiadiazole: Synthesis, crystal structures and fluorescence properties

Effectively constructing Cu I /Ag I -based coordination polymers containing Hmthd ligands is a challenging work, here, four new coordination compounds [Cu(Hmthd) 2 Cl] n ( 1 ), [Cu 3 (mthd) 2 Br] n ( 2 ), [Ag(mthd)] n ( 3 ) and [Ag 2 (mthd)I] n ( 4 ) have been obtained by reactions of the corresponding metal salts and 2-mercapto-5-methyl-1,3,4-thiadiazole (Hmthd) ligand under solvothermal conditions. All the compounds were fully characterized by single-crystal X-ray diffraction, elemental analysis, IR spectrum, thermalgravimetric analysis and powder X-ray diffraction. Compound 1 is a mononuclear coordination compound, in which two neutral Hmthd molecules and CuCl unit are coplanar. In compound 2, the anionic [CuBr(mthd)] 2 2– units and one-dimensional coplanar cationic {[Cu 2 (mthd)] + } n chains are connected to each other to form a two-dimensional layered structure. In compound 3, two different one-dimensional puckered [Ag(mthd)] n chains are connected to each other to form a two-dimensional irregular layered structure, in which a (AgS) n chain constructed by staggered Ag 3 S 3 rings is observed. Compound 4 is a two-dimensional double layer coordination framework containing a two-dimensional inorganic (Ag 2 IS) n double layer. Compound 4 shows the apparent yellow emission with the maximum at 551 nm while exciting at 333 nm, and displays sensitive luminescence quenching response to nitrobenzene with quenching constant (K sv ) of 5.07 × 10 3 M −1 and detection limit of 5.33 × 10 −6 M. This research provides a new strategy to construct the Cu I /Ag I -based coordination compounds containing Hmthd ligands with extended structures through the synergistic effect of (mthd) - and halide ions.