A new optical/electrochemical Na+ sensor based on platinum(II) complexes containing crown ether annelated dithiolate ligands

Two new platinum(II) complexes containing both 4,4'-di-tert-butyl-2,2'-bipyridine (dbbpy) and crown ether annelated dithiolate ligands, [Pt(dbbpy)(3O-C2S4)] (1, 3O-C2S42- = 1,4,7-trioxa-10,13-dithiacyclopentadec-11-ene-11,12-dithiolate) and [Pt(dbbpy)(4O-C2S4)] (2, 4O-C2S42- = 1,4,7,10-tetraoxa-13,16-dithiacyclooctadec-14-ene-14,15-dithiolate), have been prepared and characterized. These two complexes show intense electronic absorption bands in the UV-vis region due to the intramolecular mixed metal/ligand-to-ligand charge transfer transition, and they display solvatochromic behavior. The redox properties of these compounds have been investigated by cyclic voltammetry and complex 2 shows a significant response for Na+ ions with a large positive shift of ca. 125 mV. Moreover, complex 2 is very sensitive in detecting Na+ cations with an obvious change in color which can be conveniently observed with the naked eye.