Polymer-metal complexes and their catalytic activity

A polymer–metal complex is a metal complex containing a polymer ligand, showing a remarkably specific structure in which central metal ions are surrounded by a colossal polymer chain. Based on this polymeric ligand, the polymer–metal complex has interesting and important characteristics, especially catalytic activities. This activity is different from that of the corresponding ordinary metal complex of low molecular weight. In this work we studied the synthesis and characterization, in the solid state, of different poly(vinyl pyrrolidone)–cobalt (PVP/Co) and –copper (PVP/Cu) complexes. We used differential thermal analysis and FTIR as the experimental techniques. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1512–1518, 2004

Study of complexes of poly(vinyl pyrrolidone) with copper and cobalt on solid state

Temperature dependence in charge hopping between redox centers in a polymer membrane as studied by potential-step chronocoulospectrometry

Reactivity and physico-chemical properties of nitrogen-containing carbon-chain polymers in aqueous solutions

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.

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

Water-soluble Co(III)–PVP complexes (where PVP = poly-4-vinylpyridine) were prepared, and the specific rates and activation parameters for the iron(II) reductions of cis-Co(en)2XCl2+ (where X = PVP or pyridine and en = ethylenediamine) were determined in dilute sulfuric acid solutions. Under the conditions [H2SO4] = 0.50M, Σ[SO42−] = 1.25 M at 25°C, the second-order rate constants and activation entropies, respectively, for the cis-Co(en)2−XCl2+ are (4.10 ± 0.05) × 10−3l./mole-sec and −14 ± 0.6 eu for × = pyridine, (2.1 ± 0.1) × 10−3l./mole-sec and −6.0 ± 1 eu for × = PVP (Pn = 19), and (2.42 ± 0.08) × 10−3 l./mole-sec and −2.5 ± 0.8 eu for × = PVP (Pn = 98), where Pn is the degree of polymerization of the PVP. The main feature of the polymer effect in the electron-transfer reactions of the PVP complexes in which uncoordinated pyridine rings are present may be attributed to greater activation entropy. Such a greater entropy for the PVP complex may be partly ascribed to the intricate structure of the PVP ligand in the solution.

Effect of the polymeric ligand on electron-transfer reactions: Iron(II) reduction of cis-chloropoly-4-vinylpyridinebis(ethylenediamine)-cobalt(III) complexes

Kazuo Yamada

Papers

Effect of the polymeric ligand on electron-transfer reactions: Iron(II) reduction of cis-chloropoly-4-vinylpyridinebis(ethylenediamine)-cobalt(III) complexes