Synthesis, structural and photo-physical studies of bismuth(iii) complexes with Janus scorpionate and co-ligands

Abstract

Some novel complexes of bismuth(III) with the Janus scorpionate ligand [HB(mtda^Me)₃]⁻ (mtda^Me = 2-mercapto-5-methyl-1,3,4-thiadiazolyl) were synthesised. Na[HB(mtda^Me)₃] (1) was reacted with BiX₃ (X = Cl, I, NO₃) in the molar ratio 2 : 1 to afford the bismuth complexes {HB(mtda^Me)₃}₂BiCl (3), Na[{HB(mtda^Me)₃}₂BiI₂] (4) and [{HB(mtda^Me)₃}₂Bi(NO₃)]_n (5). Two mixed complexes {HB(mtda^Me)₃}Bi(phen)Cl₂ (6) and {HB(mtda^Me)₃}Bi(bipy)Cl₂ (7) were obtained using Janus scorpionate as the primary ligand in the presence of 1,10-phenanthroline and 2,2′-bipyridyl, respectively, as co-ligands in the 1 : 1 ratio. The obtained complexes were characterised by ¹H, ¹³C and diffusion NMR (DOSY), elemental analyses and mass spectrometry. Structures of the compounds NBu₄[HB(mtda^Me)₃] (2), 3, 4, 5, 6 and 7 were determined by single crystal X-ray diffraction. The molecular dynamic process in complex 3 was also studied by variable temperature NMR measurements. All bismuth complexes, except for the polymeric 5, are monomeric. Complexes 6 and 7 exhibit (B)H⋯Bi distances of 2.76(3) and 2.71(2) Å length, respectively. Compounds 2, 6 and 7 were screened for their luminescence activity. At 77 K in ethanol solution, complexes 6 and 7 exhibit phosphorescence from ligand-to-ligand charge transfer (LLCT) and the ligand-centred (LC) excited state, respectively.