Hydrothermal syntheses, crystal structures and properties of two H2Tiron-bridged rare earth metal dinuclear complexes with 1,10-phenanthroline ligands

Two isostructural rare earth metal compounds, [RE2(H2Tiron)3(phen)2] (RE = Ho (1), Lu (2)) (Na2H2Tiron = 4,5-dihydroxy-1,3-benzenedisulfonic acid disodium salt, phen = 1,10-phenanthroline), have been synthesized by hydrothermal methods and characterized by single-crystal X-ray diffraction, elemental and thermogravimetric analyses. Compounds 1 and 2 occur in the same triclinic crystal system and P-1 space group, where three H2Tiron2- ligands show the same bridged coordination mode. The dinuclear centers show double-capped triangular prismatic and dodecahedral geometries, respectively. The dinuclear compounds are stitched together via π-π stacking interactions to form 1 D chain structures. Compounds 1 and 2 have good thermal stability, which may be attributed to the introduction of phen auxiliary ligands. The emission spectrum of 1 exhibits four obvious peaks centered at 355 nm, 458 nm, 625 nm and 733 nm. The magnetic coupling interactions between Ho ions are ferromagnetic in 1.