An ESR study of polymer-Cu(II) complexes in poly(vinyl alcohol), polyacrylamide,and poly(vinyl pyrrolidone) films |
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Authors: | Osao Sumita Atsuo Fukuda Eiichi Kuze |
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Abstract: | Optical and ESR spectra of polymer-Cu(II) complexes in polymer films have been studied. The dependence on F1 = Cu2+]/MU] and F2 = OH?]/Cu2+], where MU] is the molar concentration of monomeric units of the polymer, has been obtained. Optical spectra and potentiometric titration curves in solution have also been studied. There exists a buffer region 0 ? F2 ? 2. Optical spectra in films are slightly different from those in solutions. At least five different ESR signals, designated as A, B, C or D, and E, have been found in poly(vinyl alcohol)-Cu(II). These signals appear successively with increasing F2. Assignments are proposed as follows. Signal A (F2 ≈ 0), also found in poly(acrylamide)-Cu(II) and poly(vinyl pyrrolidone)-Cu(II), is due to a single Cu(II) coordinated with two water molecules and chelated with two oxygens or nitrogens attached to the polymer. A chain of Cu(II) ions singly and double bridged with OH? ions is responsible for the B signal (F2 ≈ 1). The C and D signals (F2 ≈ 2) appear to be caused, respectively, by a dimeric Cu(II) complex singly or doubly bridged with OH? ions. The E signal (F2 ≈ 7) appears to be due to a monomeric Cu(II) complex, different from that responsible for the A signal. |
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