Syntheses, crystal structures and properties of three compounds based on the dicarboxylate ligand with S-S flexible linkage

Abstract

Three new compounds, [MnL(2,2΄-bipy)2]n·1.5nH2O (1), Co(4,4ˊ-bipy)(H2O)4·2HL (2) and 2HL·(4,4ˊ-bipyH)·2H2O (3) (H2L = 2,2΄-dithiosalicylic acid, 2,2΄-bipy = 2, 2΄-bipyridine, 4,4΄-bipy = 4,4΄-bipyridine), have been synthesized by hydrothermal and evaporation methods. Structural determination reveals that compound 1 shows a one-dimensional chain structure with L2- ligands adopting bridging coordination modes, compound 2 features a mononuclear structure with uncoordinated HL- anions, balancing the charges, compound 3 is a new inclusion compound of HL- anions and 4,4ˊ-bipyH cation with π-π stacking interactions. In compounds 1-3, the flexible S-S linkages can make H2L ligands present different conformations of dihedral angles between the terminal benzene rings. The S-O hypervalent bonds can stabilize the conformations. Thermogravimetric analyses and fluorescence measurements of compounds 1 and 2 have been performed. Compounds 1 and 2 exhibit broad blue fluorescent emission bands at 420 nm and 424 nm, respectively.