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

Abstract

Effectively constructing CuI/AgI-based coordination polymers containing Hmthd ligands is a challenging work, here, four new coordination compounds [Cu(Hmthd)2Cl]n (1), [Cu3(mthd)2Br]n (2), [Ag(mthd)]n (3) and [Ag2(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)]22– units and one-dimensional coplanar cationic {[Cu2(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 Ag3S3 rings is observed. Compound 4 is a two-dimensional double layer coordination framework containing a two-dimensional inorganic (Ag2IS)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 (Ksv) of 5.07 × 103 M−1 and detection limit of 5.33 × 10−6 M. This research provides a new strategy to construct the CuI/AgI-based coordination compounds containing Hmthd ligands with extended structures through the synergistic effect of (mthd)- and halide ions.