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

Abstract Heteroleptic chelate complexes with a [P 2 PtS 2 ] 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 C S moiety in the dmit ligand observed at 464 nm ( e  = 1.2 × 10 4  M − 1  cm − 1 ) showed a bathochromic shift to 537 nm ( e  = 0.8 × 10 4  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 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).