Hg(II) sensing properties of (diphosphine)Pt(dmit) complexes (dmit: C3S5~(2-): l,3-dithiole-2-thione-4,5-dithiolate)

摘要

Heteroleptic chelate complexes with a [P2PtS2] core, (dppf)Pt(dmit) (1) and (dppe)Pt(dmit) (2), where dppf is l,l'-bis(diphenylphosphino)ferrocene and dmit is l,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 C=S moiety in the dmit ligand observed at 464 nm (ε=1.2×10~4 M~(-1) cm~(-1)) showed a bathochromic shift to 537 nm (ε=0.8×10~4 M~(-1)cm~(-1)) as [Hg(H)]/[l] 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 C=S moiety. The affinity of (1) and (2) toward Hg(II) ion was estimated as K_d = 5.74 (±0.40)×10~(-3) M for (1) and K_d = 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).