Electrogenerated Chemiluminescence of Platinum(II) Alkynyl Terpyridine Complex with Peroxydisulfate as Coreactant

A Pt(II) alkynyl terpyridine complex containing a carbazole moiety, [Pt((t)Bu(3)tpy)(C C-C6H4-4-carbazole-9)](+) ((t)Bu(3)tpy = 4,4',4 ''-tri-tert-butyl-2,2':6',2 ''-terpyridine) 1, has been synthesized and characterized. The photophysical behavior has been studied, and the molecular structure has been determined by X-ray crystallography. The complex was found to exhibit intense electrogenerated chemiluminescence (ECL) using peroxydisulfate (S2O82-) as coreactant in acetonitrile/water (1-25%, v/v) mixture at both glassy carbon and gold electrodes, representing the first ECL example of the Pt(II) alkynyl family. The ECL was produced at potential corresponding to the first reduction wave (-0.90 V vs SCE), significantly shifted by similar to 0.65 V toward more positive potential compared with that of [Ru(bpy)(3)](2+) (bpy = 2,2'-bipyridine). The ECL spectrum was found to be identical to the photoluminescence spectrum recorded in the same medium, indicating the formation of the same excited state of d pi(Pt)->pi*((t)Bu(3)tpy)(MLCT)-M-3 mixed with pi(C CR)->pi*((t)Bu(3)tpy) (LLCT)-L-3 in both cases. The ECL mechanism was proposed involving the formation of the strongly oxidizing intermediate, SO4 center dot-, mainly generated during the catalytic reduction of S2O82- by the electrogenerated 1(-). Chemiluminescence of 1/S2O82- based on reduction with Al metal is also described.