Hg(II) sensing properties of (diphosphine)Pt(dmit) complexes (dmit: C3S52 −: 1,3-dithiole-2-thione-4,5-dithiolate)

Heteroleptic chelate complexes with a [P2PtS2] core, (dppf)Pt(dmit) (1) and (dppe)Pt(dmit) (2), where dppf is 1,1′-bis(diphenylphosphino)ferrocene and dmit is 1,3-dithiole-2-thione-4,5-dithiolate, were shown to exhibit colorimetric sensing properties for the Hg(II) ion. The absorption peak for the π → π* transition of the CS moiety in the dmit ligand observed at 464 nm (ε = 1.2 × 104 M− 1 cm− 1) showed a bathochromic shift to 537 nm (ε = 0.8 × 104 M− 1 cm− 1) as [Hg(II)]/[1] was increased up to 300, which was accompanied by color change from yellow to purple. These changes resulted from the binding of Hg(II) ions to the CS moiety. The affinity of (1) and (2) toward Hg(II) ion was estimated as Kd = 5.74 (± 0.40) × 10− 3 M for (1) and Kd = 5.60 (± 0.38) × 10− 3 M for (2). The metal- and dithiolate-substitutes of compound (1), (dppf)Ni(dmit) (3) and (dppf)Pt(bdt) (4) where bdt is 1,2-benzenedithiolate, showed no Hg(II)-sensing ability due to the instability of (3) in solution and a lack of a Hg(II)-binding site for (4). The Hg(II)-sensing selectivity for (1) and (2) was also confirmed when compared to other metal ions, such as Cr(III), Fe(II), Co(II), Cu(II), Zn(II) and Ag(I).

Heteroleptic diphosphine complexes with P2Pt(II)S2 core, (dppf)Pt(dmit) and (dppe)Pt(dmit), have the Hg(II)-sensing properties, showing a bathochromic shift of absorption peak for the π → π* transition of the dmit ligand due to intermolecular CS···Hg(II) interaction and a vivid color change from yellow to purple when [Hg2+]/[complex] was increased.Figure optionsDownload as PowerPoint slideHighlights
► Heteroleptic (diphosphine)Pt(dmit) is investigated for its Hg(II)-sensing properties.
► The interaction of (dmit)S···Hg(II) causes a bathochromic shift in UV–vis spectra.
► The solution color is changed from yellow to purple as the [Hg2+] is increased.
► The Hg(II) ion selectively changes the solution color.