A computational and experimental study on the Jahn-Teller effect in the hydrated copper (II) ion. Comparisons with hydrated nickel (II) ions in aqueous solution and solid Tutton's salts

Ab initio SCF molecular orbital calculations have been performed on the free Cu(OH2)62+ complex in D2h symmetry. Two extrema in the adiabatic electron energy potential surface were obtained corresponding to a tetragonal distortion from the regular Th symmetry of the octahedral complex, as expected from the Jahn-Teller theorem in a case with strong E-e type vibronic coupling. The tetragonally elongated octahedral structure with Cu-20ax at 2.25 AA and Cu-40eq at 2.06 AA gave a slightly lower energy (72 cm-1) than the compressed geometry with Cu-20ax at 2.02 AA and Cu-40eq at 2.17 AA. The calculated Jahn-Teller energy is 650 cm-1 from that of the regular Th symmetry with Cu-60 at 2.115 AA. EXAFS measurements were performed on aqueous Cu2+ solutions and showed a greater distortion with Cu-40eq at 1.99 AA and Cu-20ax at about 2.29 AA. Infrared absorption spectroscopic measurements were made on the O-D stretching vibrations of HDO molecules in aqueous Cu2+ and Ni2+ solutions with added D2O in order to study the hydrogen bonds from the hydrated ions. A distorted Cu(OH2)62+ ion is expected to form hydrogen bonds of unequal strength because of the stronger polarisation of the more strongly bonded equatorial water molecules. Two bands ascribed to the hydration of the Cu2+ ion were obtained, the more intense corresponding to the strongest hydrogen bonds at approximately=2400 cm-1, and the weaker at approximately=2530 cm-1, whereas for Ni2+ only one band at approximately=2420 cm-1 was found. With the use of a correlation between RO...O versus nu OD from crystal structure data the mean hydrogen-bonded O...O distances to the second hydration shell are estimated to about 2.74 AA from the equatorial water molecules and 2.88 AA from the axial. The IR data show that the distortions induced by the Jahn-Teller effect on the second hydration sphere are visible on a vibrational timescale, despite the fast intramolecular inversion of the distortion axis between the three principal octahedral directions. The splitting of the nu OD bands in the Tutton salts Cs2(M(OH2)6)(SO4)2, M=Cu or Ni, with some added D2O has also been measured and compared to crystal structure data of the hydrogen bonded distances. The separation of about 107 cm-1 between the two groups of O-D stretching vibrations found in the Cu salt can be ascribed to a static Jahn-Teller effect.

[1]  A. Hewat,et al.  Temperature dependence of the structure and bonding in deuterated Cu(II) Tutton's salt , 1984 .

[2]  W. S. Benedict,et al.  Rotation‐Vibration Spectra of Deuterated Water Vapor , 1956 .

[3]  G. Brown,et al.  The structure of copper ammonium sulfate hexahydrate from neutron diffraction data , 1969 .

[4]  Arne Holm,et al.  Jahn-Teller Distortion in Copper(II) Complexes. Why Tetragonal Elongation Is Preferred to Tetragonal Compression. , 1979 .

[5]  Magnus Sandström,et al.  Neutron diffraction study of aqueous transition metal salt solutions by isomorphic substitution , 1981 .

[6]  J. Enderby,et al.  The structure of Cu2+ aqueous solutions , 1988 .

[7]  E. N. Maslen,et al.  Electron density in non‐ideal metal complexes. IV. Hexaaquametal(II) ammonium sulfates , 1988 .

[8]  Z. Luz,et al.  ESR and NMR in Aqueous and Methanol Solutions of Copper(II) Solvates. Temperature and Magnetic Field Dependence of Electron and Nuclear Spin Relaxation , 1972 .

[9]  M. Magini,et al.  Coordination Of Copper II In Aqueous CuSO4 Solution , 1983 .

[10]  H. Oberhammer,et al.  I. Hargittai, M. Hargittai (Eds.): The Electron Diffraction Technique, Part A von: Stereochemical Applications of Gas‐Phase Electron Diffraction, VCH Verlagsgesellschaft, Weinheim, Basel. Cambridge, New York 1988. 206 Seiten, Preis: DM 210,‐. , 1989 .

[11]  B. Hathaway.  A new look at the stereochemistry and electronic properties of complexes of the copper(II) ion , 1984 .

[12]  SanoMitsuru,et al.  POTENTIAL ENERGY SURFACE OF [Cu(H2O)6]2+ AND [Zn(H2O)6]2+ DERIVED FROM AB INITIO MO CALCULATIONS , 1980 .

[13]  J. Lindgren,et al.  Hydration of ions in aqueous solutions studied by infrared spectroscopy. II: Application , 1984 .

[14]  L. Pettersson,et al.  Effective core potential parameters for first‐ and second‐row atoms , 1987 .

[15]  E. N. Maslen,et al.  Crystal structure and electron density of diammonium hexaaquacopper(II) sulfate , 1988 .

[16]  Toshio Yamaguchi,et al.  X-Ray Diffraction Studies of the Structures of Hydrated Divalent Transition-Metal Ions in Aqueous Solution , 1976 .

[17]  M. Sano,et al.  The exafs study of Cu(II) aqueous solution using a position sensitive detector. , 1980 .

[18]  J. Lindgren,et al.  Hydration of ions in aqueous solutions studied by infrared spectroscopy. I: Method , 1984 .

[19]  G. Greaves,et al.  Detection of Mn–Br bonds in aqueous MnBr2 solution by X-ray absorption spectroscopy , 1983 .

[20]  M. Magini.  Coordination of copper(II). Evidence of the Jahn-Teller effect in aqueous perchlorate solutions , 1982 .

[21]  小杉 信博.  B. K. Teo: EXAFS; Basic Principles and Data Analysis, Springer-Verlag, Berlin and Heidelberg, 1986, xviii+350ページ, 25×17cm, 18,198円 (Inorganic Chemistry Concepts, 9). , 1987 .

[22]  B. Silver,et al.  ESR of Cu2+(H2O)6. II. A quantitative study of the dynamic Jahn‐Teller effect in copper‐doped zinc Tutton's salt , 1974 .

[23]  H. Ohtaki,et al.  An X-Ray Diffraction Study of the Structure of Hydrated Copper(II) Ion in a Copper(II) Perchlorate Solution , 1974 .

[24]  J. Lindgren,et al.  A quantitative infrared spectroscopic method for the study of the hydration of ions in aqueous solutions , 1988 .

[25]  L. Pettersson,et al.  Effective core potential calculations using frozen orbitals. Applications to transition metals , 1983 .

[26]  M. Eisenstein.  Static deformation densities for cytosine and adenine. , 1988, Acta crystallographica. Section B, Structural science.

[27]  J. B. Hastings,et al.  Application of the EXAFS method to Jahn—Teller ions: static and dynamic behavior of Cu(H2O)62+ and Ci(H2O)2+6 in aqueous solution , 1981 .

[28]  A. Veillard,et al.  Gaussian basis sets for molecular wavefunctions containing third-row atoms , 1971 .

[29]  E. N. Maslen,et al.  The structures of Tutton's salts. I: Diammonium hexaaquamagnesium(II) sulfate , 1988 .

[30]  R. A. Scott.  [23] Measurement of metal-ligand distances by EXAFS , 1985 .

[31]  W. Howells,et al.  The dynamics of water molecules in ionic solution. II. Quasi-elastic neutron scattering and tracer diffusion studies of the proton and ion dynamics in concentrated Ni2+, Cu2+ and Nd3+ aqueous solutions , 1987 .

[32]  M. Riley,et al.  Interpretation of the temperature dependent g values of the Cu(H2O)2+6 ion in several host lattices using a dynamic vibronic coupling model , 1987 .

[33]  M. C. Feiters,et al.  Coordination chemistry of higher oxidation states. 19. Synthesis and properties of diphosphine and diarsine complexes of iron(IV), and iron K-edge EXAFS data on [Fe(o-C6H4(PMe2)2)2Cl2]n+[BF4]n (n = 0-2) , 1986 .

[34]  I. Bersuker,et al.  The Jahn-Teller Effect and Vibronic Interactions in Modern Chemistry , 1984 .

[35]  H. Wakita,et al.  An EXAFS Investigation of the Coordination Structure of Copper(II) Ions in Aqueous Cu(ClO4)2 and Methanolic CuCl2 Solutions , 1986 .

[36]  J. Lindgren,et al.  On the correlation between deuteron quadrupole coupling constants, O-H and O-D stretching frequencies and hydrogen-bond distances in solid hydrates , 1978 .

[37]  E. C. Lingafelter,et al.  The crystal structure of Tutton's salts. I. Zinc ammonium sulfate hexahydrate , 1964 .

[38]  M. Nomura,et al.  Concentration dependence of EXAFS and XANES of copper(II) perchlorate aqueous solution: comparison of solute structure in liquid and glassy states , 1988 .

[39]  N. Skipper,et al.  DIFFRACTION AND THE STUDY OF AQUA IONS , 1987 .