Structural Chemistry

, Volume 30, Issue 1, pp 61–74 | Cite as

Determination of structures of cupric-chloro complexes in hydrochloric acid solutions by UV-Vis and X-ray absorption spectroscopy

  • Masahito UchikoshiEmail author
  • Kozo Shinoda
Original Research


Ultrahigh-purity metals are indispensable to understanding the nature of materials, but the purity of contemporary metals is insufficient for determining their intrinsic properties. The fundamentals of the anion-exchange reaction must be clear in order to increase the refining efficiency of anion-exchange separation for purification of metals. The thermodynamic analysis of the anion-exchange reaction needs to take account of the distributions of metal-chloro complexes in the solution phase in addition to those between the resin and the solution phase. The structures of metal-chloro complexes in the solution phase must be determined as the first step in determining what species is adsorbed on the resin. Copper is one of the base metals most commonly used in modern society, and the anion-exchange behavior of cupric species is representative. The distribution and the molar attenuation coefficients of cupric-chloro complexes in hydrochloric acid solutions were obtained employing factor analysis followed by fitting a thermodynamic model to ultraviolet-visible absorption spectra. The cumulative formation constants were determined as follows: \(\log _{10}\beta _{1} = 0.599\), \(\log _{10}\beta _{2} = 0.343\), \(\log _{10}\beta _{3} = -1.88\), and \(\log _{10}\beta _{4} = -5.25\), and the Setchénow coefficient for the neutral species of [CuIICl2]0 is 0.188. Using the distribution assessed by the above thermodynamic parameters, the X-ray absorption spectra (XAS), consisting of X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) of individual species, were assessed by factor analysis. EXAFS theoretical models were fitted to experimental spectra of individual species to determine their structures and coordination geometries for the first time, although it is generally very difficult to obtain the spectrum of the individual species in a matrix containing other species simultaneously. The structures of five cupric-chloro complexes were determined to be distorted octahedrons of \(\left [\mathrm {Cu^{II}(H_{2}O)_{4}^{eq}(H_{2}O)_{2}^{ax}}\right ]^{2+}, \left [\mathrm {Cu^{II}(H_{2}O)_{4}^{eq}(H_{2}O)^{ax}Cl^{ax}}\right ]^{+}\), and \(\left [\mathrm {Cu^{II}Cl_{2}^{ax}(H_{2}O)_{4}^{eq}}\right ]^{0}\), a planar triangle of \(\left [\mathrm {Cu^{II}Cl_{3}}\right ]^{-}\), and a tetrahedron of [CuIICl4]2−. The obtained spectra can be used as standards. The XANES spectra of cupric-chloro complexes were interpreted qualitatively. The Cl ligand in \(\left [\mathrm {Cu^{II}(H_{2}O)_{4}^{eq}(H_{2}O)^{ax}Cl^{ax}}\right ]^{+}\) is attracted to the center atom of CuII by electrostatic force, as the H2O ligands are. Contrastingly, the bonding system of the Cl ligands in the latter three species involves covalency.


Cupric-chloro complexes Hydrochloric acid solution Factor analysis Multivariate curve resolution-alternating least squares Ultraviolet-visible absorption spectrum X-ray absorption spectrum Extended X-ray absorption fine structure X-ray absorption near edge structure 



The authors wish to thank Mr. Yuji Baba and Mr. Kouji Nagahashi for their great devotion to this experimental work. The synchrotron radiation experiments of X-ray absorption spectrometry were performed at BL14B2 of SPring-8 with the approval of the Japan Synchrotron Radiation Research Institute (Proposal No. 2008A1941). This work was performed under the Research Program of “The Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials” in “The Network Joint Research Center for Materials and Devices” and as one of the projects in the MSTeC Research Center at the Institute of Multidisciplinary Research for Advanced Materials, Tohoku University.

Author Contributions

The manuscript was composed by contributions of all authors. All authors have given approval to the final version of the manuscript.

Compliance with Ethical Standards

Conflict of interests

The authors declare that they have no conflict of interest.


  1. 1.
    Isshiki M, Igaki K (1979) Preparation and some characteristic properties of high purity iron. Technology reports Tohoku University 44(2):331–355Google Scholar
  2. 2.
    Sugimoto K, Matsuda S, Isshiki M, Ejima T, Igaki K (1982) Corrosion characteristics of high purity iron. J Jpn Inst Met 46(2):155–161. CrossRefGoogle Scholar
  3. 3.
    Kékesi T, Mimura K, Isshiki M (2002) Ultra-high purification of iron by anion exchange in hydrochloric acid solutions. Hydrometall 63(1):1–13. CrossRefGoogle Scholar
  4. 4.
    Uchikoshi M, Shibuya H, Kékesi T, Mimura K, Isshiki M (2009) Mass production of high-purity iron using anion-exchange separation and plasma arc melting. Metall Mater Trans B 40(5):615–618. CrossRefGoogle Scholar
  5. 5.
    Kékesi T, Uchikoshi M, Mimura K, Isshiki M (2001) Anion-exchange separation in hydrochloric acid solutions for the ultrahigh purification of cobalt. Metall Mater Trans B 32 (4):573–582. CrossRefGoogle Scholar
  6. 6.
    Uchikoshi M, Shibuya H, Imaizumi J, Kékesi T, Mimura K, Isshiki M (2010) Preparation of high-purity cobalt by anion-exchange separation and plasma arc melting. Metall Mater Trans B 41(2):448–455. CrossRefGoogle Scholar
  7. 7.
    Kékesi T, Mimura K, Ishikawa Y, Isshiki M (1997) Preparation of ultra-high-purity copper by anion exchange. Metall Mater Trans B 28(6):987–993. CrossRefGoogle Scholar
  8. 8.
    Uchikoshi M, Kékesi T, Ishikawa Y, Mimura K, Isshiki M (1997) Copper purification by anion-exchange separation in chloride media. Mater trans JIM 38(12):1083–1088. CrossRefGoogle Scholar
  9. 9.
    Gotoh K, Suzuki H, Udono H, Kikuma I, Esaka F, Uchikoshi M, Isshiki M (2007) Single crystalline β −FeSi 2 grown using high-purity F e S i 2 source. Thin Solid Films 515(22):8263–8267. CrossRefGoogle Scholar
  10. 10.
    Brugger J, McPhail DC, Black J, Spiccia L (2001) Complexation of metal ions in brines: application of electronic spectroscopy in the study of the Cu(II)-LiCl-H2O system between 25 and 90∘. Geochim Cosmochim Acta 65(16):2691–2708. CrossRefGoogle Scholar
  11. 11.
    Helgeson HC, Kirkham DH (1974) Theoretical prediction of thermodynamic behavior of aqueous electrolytes at high pressures and temperatures. Am J Sci 274(10):1199–1261. CrossRefGoogle Scholar
  12. 12.
    Uchikoshi M (2017) Determination of the distribution of cupric chloro-complexes in hydrochloric acid solutions at 298 K. J Solut Chem 46(3):704–719. CrossRefGoogle Scholar
  13. 13.
    Bunker G (2010) Introduction to XAFS. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  14. 14.
    Gemperline PJ (ed) (2006) Practical guide to chemometrics, 2nd edn. Taylor & Francis Group, Boca RatonGoogle Scholar
  15. 15.
    Calvin S (2013) XAFS For everyone. CRC Press, Boca RatonCrossRefGoogle Scholar
  16. 16.
    Ueno K (1976) Chelate titration methods. Nan-e dou, TokyoGoogle Scholar
  17. 17.
    Zabinsky SI, Rehr JJ, Ankudinov A, Albers RC, Eller MJ (1995) Multiple-scattering calculations of x-ray-absorption spectra. Phys Rev B Condens Matter Mater Phys 52(4):2995–3009. CrossRefGoogle Scholar
  18. 18.
    Jaumot J, de Juan A, Tauler R (2015) MCR-ALS GUI 2.0: New Features and applications. Chemometrics Intell Lab Syst 140:1–12. CrossRefGoogle Scholar
  19. 19.
    Bjerrum J (1987) Determination of small stability constants. A spectrophotometric study of copper(ii) chloride complexes in hydrochloric acid. Acta Chem Scand A 41A:328–334. CrossRefGoogle Scholar
  20. 20.
    Sverjensky DA, Shock EL, Helgeson HC (1997) Prediction of the thermodynamic properties of aqueous metal complexes to 1000C and 5 kbar. Geochim Cosmochim Acta 61(7):1359–1412. CrossRefGoogle Scholar
  21. 21.
    Ravel B, Newville M (2005) ATHENA, ARTEMIS, HEPHAESTUS: data analysis for x-ray absorption spectroscopy using IFEFFIT. J Synchrotron Rad 12:537–541. CrossRefGoogle Scholar
  22. 22.
    Shadle SE, Penner-Hahn JE, Schugar HJ, Hedman B, Hodgson KO, Solomon EI (1993) X-ray absorption spectroscopic studies of the blue copper site: Metal and ligand K-edge studies to probe the origin of the EPR hyperfine splitting in plastocyanin. J Am Chem Soc 115(2):767–776. CrossRefGoogle Scholar
  23. 23.
    Pickering IJ, George GN (1995) Polarized x-ray absorption spectroscopy of cupric chloride dihydrate. Inorg Chem 34(12):3142–3152. CrossRefGoogle Scholar
  24. 24.
    Gaur A, Klysubun W, Nair NN, Shrivastava BD, Prasad J, Srivastava K (2016) XAFS Study of copper(II) complexes with square planar and square pyramidal coordination geometries. J Mol Struct 1118 (C):212–218. CrossRefGoogle Scholar
  25. 25.
    Newville M, Lı̄viṅs P, Yacoby Y, Rehr JJ, Stern EA (1993) Near-edge x-ray-absorption fine structure of Pb: A comparison of theory and experiment. Phys Rev B Condens Matter Mater Phys 47(21):14126–14131. CrossRefGoogle Scholar
  26. 26.
    Malinowski ER, Howery DG (1980) Factor analysis in chemistry, 3rd edn. Wiley, New YorkGoogle Scholar
  27. 27.
    Filipponi A, D’Angelo P, Pavel NV, Cicco AD (1994) Triplet correlations in the hydration shell of aquaions. Chem Phys Lett 225(1-3):150–155. CrossRefGoogle Scholar
  28. 28.
    D’Angelo P, Bottari E, Festa MR, Nolting HF, Pavel NV (1997) Structural investigation of copper(II) chloride solutions using x-ray absorption spectroscopy. J Chem Phys 107(8):2807–2812. CrossRefGoogle Scholar
  29. 29.
    Yi HB, Xia FF, Zhou Q, Zeng D (2011) [CuCl3] and [CuCl4]2− hydrates in concentrated aqueous solution: A density functional theory and ab initio study. J Phys Chem A 115(17):4416–4426. CrossRefGoogle Scholar
  30. 30.
    Partanen JI, Juusola PM, Vahteristo KP, de Mendonca AJG (2007) Re-evaluation of the activity coefficients of aqueous hydrochloric acid solutions up to a molality of 16.0 mol⋅kg − 1 using the Hückel and Pitzer equations at temperatures from 0 to 50C. J Solut Chem 36(1):39–59. CrossRefGoogle Scholar
  31. 31.
    Fulton JL, Hoffmann MM, Darab JG (2000) An X-ray absorption fine structure study of copper(I) chloride coordination structure in water up to 325°C. Chem Phys Lett 330(3-4):300–308. CrossRefGoogle Scholar
  32. 32.
    Ohtaki H, Maeda M (1974) An x-ray diffraction study of the structure of hydrated copper(II) Ion in a copper(II) perchlorate solution. Bull Chem Soc Jpn 47(9):2197–2199. CrossRefGoogle Scholar
  33. 33.
    Ohtaki H, Yamaguchi T, Maeda M (1976) X-Ray diffraction studies of the structures of hydrated divalent transition-metal ions in aqueous solution. Bull Chem Soc Jpn 49(3):701–708. CrossRefGoogle Scholar
  34. 34.
    Xia FF, Yi HB, Zeng D (2010) Hydrates of cu2+ and cucl+ in dilute aqueous solution: A density functional theory and polarized continuum model investigation. J Phys Chem A 114(32):8406–8416. CrossRefGoogle Scholar
  35. 35.
    Powell KJ, Brown PL, Byrne RH, Gajda T, Hefter G, Sjöeberg S., Wanner H (2007) Chemical speciation of environmentally significant metals with inorganic ligands. Pure Appl Chem 79(5):895–950. CrossRefGoogle Scholar
  36. 36.
    Fulton JL, Hoffmann MM, Darab JG, Palmer BJ, Stern EA (2000) Copper(i) and copper(II) coordination structure under hydrothermal conditions at 325C: An x-ray absorption fine structure and molecular dynamics study. J Phys Chem A 104 (49):11651–11653. CrossRefGoogle Scholar
  37. 37.
    Bair RA, Goddard WA III (1980) Ab initio studies of the X-ray absorption edge in copper complexes. I. Atomic Cu2+ and Cu(II)Cl2. Condens Matter Mater Phys 22(6):2767–2776. CrossRefGoogle Scholar
  38. 38.
    Kosugi N, Yokoyama T, Asakura K, Kuroda H (1984) Polarized Cu K-edge XANES of square planar CuCl\(_{4}^{2-}\) ion. Experimental and theoretical evidence for shake-down phenomena. Chem Phys 91(2):249–256. CrossRefGoogle Scholar
  39. 39.
    Smith TA, Penner-Hahn JE, Berding MA, Doniach S, Hodgson KO (1985) Polarized X-Ray Absorption-Edge Spectroscopy of Single-Crystal copper(II) Complexes. J Am Chem Soc 107(21):5945–5955. CrossRefGoogle Scholar
  40. 40.
    Kau LS, Spira-Solomon DJ, Penner-Hahn JE, Hodgson KO, Solomon EI (1987) X-ray absorption edge determination of the oxidation state and coordination number of copper. Application to the type 3 site in Rhus vernicifera laccase and its reaction with oxygen. J Am Chem Soc 109(21):6433–6442. CrossRefGoogle Scholar
  41. 41.
    Hahn JE, Scott RA, Hodgson KO, Doniach S, Desjardins SR, Solomon EI (1982) Observation of an Electric Quadrupole Transition in the X-Ray Absorption-Spectrum of a Cu(II) Complex. Chem Phys Lett 88 (6):595–598. CrossRefGoogle Scholar
  42. 42.
    Scott RA, Hahn JE, Doniach S, Freeman HC, Hodgson KO (1982) Polarized x-ray absorption-spectra of oriented plastocyanin single-crystals–investigation of methionine copper coordination. J Am Chem Soc 104 (20):5364–5369. CrossRefGoogle Scholar

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Authors and Affiliations

  1. 1.Institute of Multidisciplinary Research for Advanced MaterialsTohoku UniversitySendaiJapan

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