Conformational effects of polymer chains on the electron‐transfer reactions and luminescence behavior of Ru(bpy)₃^a+ in aqueous solutions of poly(acrylic acid)‐ and poly(methacrylic acid)‐bound Co (III) complexes

Abstract

The effects of the conformation of polymer chains on the electron transfer reactions and on the luminescence behavior of Ru(bpy)32+ in aqueous solutions of cis‐Co(A)PAA and cis‐Co(A)PMA ((A) = (en)2(OH2), en = ethylenediamine, PAA = poly(acrylic acid), and PMA = poly(methacrylic acid)) have been investigated by means of several spectrophotometric techniques. The results of the electron‐transfer reactions of the polymer Co(III) complexes with Cr(bpy)32+ and Fe(edta)2− revealed that, at low pH, part of the Co(III) complex moieties could hardly be reduced even in the presence of a large excess of the reducing agents when the degree of coordination of the Co(III) complex is very low. The magnitude of the degree of reduction of the Co(III) complex and the rate constants of the electron‐transfer reactions of Co(A)PMA are considerably affected by the conformational transition of the polymer chains. The luminescence behavior of Ru(bpy)32+ in aqueous solutions of these polymer complexes at around pH 5 are essentially explained by the spontaneous luminescence decay of the ex cited state of Ru(bpy)32+ ions which are localized in the compact form of the polymer chains and that of the non‐shielded ones which have a similar lifetime as in water. Effects of the conformational transition of Co(A)PMA chain on the luminescence intensity and the lifetime of the excited state of Ru(bpy)32+ are discussed in the light of the results obtained.

Characterization of electrocatalytic proton reduction and surface adsorption of platinum nanoparticles supported by a polymeric stabilizer on an ITO electrode

“…The relatively obtuse increase of G cov for PAA-Pt nanoparticles is explained by the effect of the polymer chain of PAA, which is well-known to give the obtuse dissociation curve of PAA. 34 The adsorption isotherms of citrate-Pt and PAA-Pt nanoparticles were investigated at different temperatures from 5 to 35 C to reveal their adsorption mechanisms. G cov increased with c Pt and was saturated above 100 mM of c Pt for citrate-Pt (Fig.…”