Electrogenerated chemiluminescence of platinum(II) alkynyl terpyridine complex with peroxydisulfate as coreactant

Abstract

A Pt(II) alkynyl terpyridine complex containing a carbazole moiety, [P( tBu 3tpy)(C=C-C 6H 4-4-carbazole-9)] + ( tBu 3tpy = 4,4',4"-tri-fert-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 (S 2O 8 2-) as coreactant in acet-onitrile/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 ∼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 dπ(Pt) → π *( tBu 3tpy) 3MLCT mixed with π(C=CR)→ π *( tBu 3tpy) 3LLCT in both cases. The ECL mechanism was proposed involving the formation of the strongly oxidizing intermediate, SO 4 •-, mainly generated during the catalytic reduction of S 2O 8 2-by the electrogenerated 1 -. Chemiluminescence of 1/S 2O 8 2- based on reduction with Al metal is also described. © 2011 American Chemical Society.