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 L^2- 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 fluorescent 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.