Fig. 10
Vis absorption spectra of: a the heteroligand system in a solution containing [Co(imid)2]n and histidine at 1:5 molar ratio (starting from basic solution of pH 8.64; curve 1). C Co = 3.5 × 10−2 mol L−1. Curves 2–5 denote the spectra scanned after adding a consecutive portion of acid. pH: 2–6.15; 3–5.09; 4–4.92; 5–4.20. Curve 6—absorption spectrum of the Co(II) aquo-ion; b the binary system in a solution containing Co(II) and histidine at 1:5 molar ratio (starting from acid solution of pH 3.54; curve 2). C Co = 3.5 × 10−2 mol L−1. Curves 3–6 denote the spectra scanned after adding a consecutive portion of base. pH: 3–4.61; 4–5.05; 5–6.12; 6–precipitate. Curve 1—absorption spectrum of the Co(II) aquo-ion