| | 1 | Author
| Ingmar Persson, Magnus Sandström, Haruhiko Yokoyama, Monika Chaudhry, Japan | Requires cookie* | | | Title
| S  | | | | Abstract
| tr u c tu r e o f th e S o lv a te d S tr o n tiu m a n d B a riu m I o n s in A q u e o u s, D im e th y l S u lfo x id e a n d P y r id in e S o lu tio n , a n d C r y s ta l S tr u c tu r e o f S tr o n tiu m a n d B a r iu m H y d r o x id e O c t a h y d r a te Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday Single crystal X-ray data, collected at 298 K, are used to redetermine the crystal structure of the non-isomorphic compounds [Sr(H20)8](0H)2 and [Ba(H20)8](0H)2. The eight water oxygen atoms form distorted Archimedean antiprisms around the octahydrated metal ions with mean metal ion-oxygen distances 2.62 and 2.79 Ä for strontium and barium, respectively. A second coordination shell of 24 hydrogen-bonded oxygen atoms with mean metal ion-oxygen distances M • • • O" 4.76 and 4.80 A, respectively, is observed. The hydroxide ions in both structures have an unusual hydrogen bond arrangement with 5 bonds accepted and one donated. The structure of the solvated strontium and barium ions in aqueous, dimethyl sulfoxide and pyridine solutions has been studied by means of large angle X-ray scattering and extended X-ray absorption fine structure spectroscopy techniques. In aqueous solution independent determinations of the first-sphere metal-oxygen coordination by the two techniques resulted in the bond lengths Sr-O 2.63 (2) and Ba-O 2.81 (3) A, and for both metal ions a hydration number of 8.1 (3). The second coordination spheres are very diffuse with only about 13 water molecules at similar M • • • O" distances as in the crystal structures and 2-3 water molecules closer to the metal ions. In dimethyl sulfoxide solution both ions were found to coordinate 6.0 (5) solvent molecules with the distances Sr-O 2.54(1), Sr -S 3.77(1) A, and Ba-O 2.76(1), Ba -S 3.99(1) A. For the solvated ions in pyridine solution EXAFS measurements yielded the distances Sr-N 2.57 (2) and Ba-N 2.78 (3) A, with a probable solvation number of 6. Correlations of hydration enthalpies and partial molar volumes with experimental M-O bond distances in aqueous solution are used to discuss hydration numbers and bond character for all of the alkaline earth metal ions. | | | |
Reference
| Z. Naturforsch. 50a, 21—37 (1995); received November 8 1994 | | | |
Published
| 1995 | | | |
Keywords
| Barium, Strontium, Hydration, Solvation, Structure | | | |
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| default:Reihe_A/50/ZNA-1995-50a-0021.pdf | | | | Identifier
| ZNA-1995-50a-0021 | | | | Volume
| 50 | |
| 2 | Author
| J. Barthel, K. Bachhuber, R. Büchner | Requires cookie* | | | Title
| D | | | | Abstract
| ie le c tr ic R e la x a tio n o f N a C 1 0 4 S o lu tio n s in F o r m a m id e , N -M e th y lf o r m a m id e , a n d N ,N -D im e th y lf o rm a m id e Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday Complex permittivity spectra in the frequency range 0.95 < v/[GHz] < 89 for N,N-dimethylform-amide (DMF), N-methylformamide (NMF), formamide (FA) and their solutions of NaC104 are investigated to study the change of liquid structure and dynamics arising from the availability of one hydrogen-bond acceptor site together with no (DMF), one (NMF), or two (FA) donor sites on the same molecule. Three solvent relaxation processes are observed for NMF and two for FA and DMF. The relaxation parameters are used to determine solvation numbers. They show that ion-solvent interactions lead to a reduction of the average length of the H-bonded NMF chains but have only moderate influence on the FA structure. An additional solute relaxation process in DMF solutions is due to the diffusion-controlled formation and decomposition of solvent-shared ion pairs. | | | |
Reference
| Z. Naturforsch. 50a, 65—74 (1995); received October 22 1994 | | | |
Published
| 1995 | | | |
Keywords
| Dielectric relaxation, Formamides, Solvation, Solvent dynamics, Ion association | | | |
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| default:Reihe_A/50/ZNA-1995-50a-0065.pdf | | | | Identifier
| ZNA-1995-50a-0065 | | | | Volume
| 50 | |
| 3 | Author
| Haruhiko Yokoyama, Saeko Suzuki, Masuo Goto, Kazuteru Shinozaki, Yuriko Abe, Shin-Ichi Ishiguro | Requires cookie* | | | Title
| X -R a | | | | Abstract
| y D if fr a c tio n S tu d y o f th e S o lv a tio n S tr u c tu r e o f th e C o b a lt (I I) I o n in N ,N -D im e th y lf o rm a m id e S o lu tio n Dedicated to Prof. Hitoshi Ohtaki on the occasion of his 60th birthday The solvation structure of Co2+ in N,N-dimethylformamide (DMF) has been studied by X-ray diffraction measurements on cobalt (II) and magnesium (II) Perchlorate solutions of the same concen tration, using an isostructural substitution method. The radial distribution function revealed three distinct peaks assigned to the oxygen, amido carbon (CJ, and nitrogen atoms of six planar DMF molecules in the first coordination sphere around the metal atom. The distance from the cobalt atom to each atom (O, Cx, N) is 213,299, and 423 pm, respectively. This indicates that the Co-O-Cj bond angle is 122-123° and the metal atom is close to the O-Cj-N plane of the DMF molecule. | | | |
Reference
| Z. Naturforsch. 50a, 301—306 (1995); received September 28 1995 | | | |
Published
| 1995 | | | |
Keywords
| Cobalt, N,N-dimethylformamide, Solvation, X-ray, Structure | | | |
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| default:Reihe_A/50/ZNA-1995-50a-0301.pdf | | | | Identifier
| ZNA-1995-50a-0301 | | | | Volume
| 50 | |
| 4 | Author
| JonathanM. Keske, J.Malcolm Bruce, P. Leslie, D. Utton | Requires cookie* | | | Title
| A New Method of Solvation Analysis: Applications to Quinones | | | | Abstract
| A new method o f analysis o f the factor contributing to solvation o f small molecules is de scribed. A pproxim ations o f the energetic contributions to the entry o f a molecule into water have been derived from partition coefficient data o f solutes and selected derivatives from a multiplicity o f solvents. These include taking separate account energy o f the cost o f introduction o f a molecular cavity in water, the strength o f solute-water dipolar interactions, and the strengths o f hydrogen bond formation with water o f the lone pairs and hydroxylic hydrogens associated with the molecule. In this report the solvation-free energies o f benzoquinone and hydroquinone in water are described. We also consider the solvation o f the sem iquinone anion and show it to be fundamentally different from that o f either the quinone or hydroquinone; this is discussed as a potentiality for selective binding ("solvation") o f quinone, sem iquinone and hydroquinone in sites o f redox catalysis such as those found in the photosynthetic reaction center. | | | |
Reference
| Z. Naturforsch. 45c, 430 (1990); received December 18 1989 | | | |
Published
| 1990 | | | |
Keywords
| Quinone, Ligand Binding, Reaction Centers, Solvation | | | |
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| default:Reihe_C/45/ZNC-1990-45c-0430.pdf | | | | Identifier
| ZNC-1990-45c-0430 | | | | Volume
| 45 | |
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