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1995 (1)
1994 (1)
1Author    Toshiyuki Takam, KeisukeN. Akam Ura, M. Ikito Ihara, Hisanobu Wakita, Toshio YamaguchiRequires cookie*
 Title    Raman Scattering and X-ray Diffraction Studies on Zinc(II) Bromide Solutions in Methanol and N,N-Dimethylformamide in the Temperature Range 77-333 K  
 Abstract    n Z i n c (I I) B r o m i d e S o l u t i o n s i n M e t h a n o l a n d N , N -D i m e t h y l f o r m a m i d e i n t h e T e m p e r a t u r e R a n g e 7 7 -3 3 3 K The structure o f zinc(II) brom o com plexes in m ethanol and N,N-dim ethylformam ide (D M F) (molar ratio [solvent]/[ZnBr?] = 10, temperature range 7 7 -3 3 3 K) has been investigated by Raman scattering and X-ray diffraction. In the m ethanol solution symmetric Z n -B r vibrations (vt) o f the dibrom o-and tribrom ozinc(II) com plexes were observed at 209 and 184 c m " 1, respectively. With decreasing temperature the intensity o f the vx band decreased for the dibrom o and increased for the tribromo complex. In addition, the Vj band for the tetrabromo complex appeared in the supercooled and glassy methanol solutions. In the D M F solution only one band, assigned to both the dibrom o-and tribromozinc(II) com plexes, was observed. Its intensity did not change with temper­ ature. The X-ray diffraction data revealed that the average number of Z n -B r interactions within the zinc (II) bromo com plexes does not change with temperature while the number of nonbonding Br • • • Br interactions within the com plexes increases from 1.5 at 298 K to 1.9 at 243 K for the methanol solution and from 1.3 at 298 K to 1.8 at 243 K for the D M F solution. These Raman and X-ray results have confirmed that in both m ethanol and D M F solutions at high temperatures the dibrom o species is predominantly formed, whereas at low temperatures the tribromo com plex is favored, the tetrabromo species being formed only in the supercooled and glassy m ethanol solutions. The temperature dependent equilibrium shifts of the zinc(II) bromo complexes in the methanol and D M F solutions are discussed together with previously reported results for the aqueous phase. 
  Reference    Z. Naturforsch. 49a, 1119 (1994); received O ctober 15 1994 
  Published    1994 
  Keywords    Raman spectroscopy, X-ray diffraction, Zinc(II) bromide, M ethanol, N, N -D im ethyl-formamide 
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 TEI-XML for    default:Reihe_A/49/ZNA-1994-49a-1119.pdf 
 Identifier    ZNA-1994-49a-1119 
 Volume    49 
2Author    Makoto Koide, Shin-Ichi IshiguroRequires cookie*
 Abstract    h e r m o d y n a m ic s a n d S t r u c t u r e o f I s o th io c y a n a te C o m p le x e s o f M a n g a n e s e (I I) , C o b a l t(I I) a n d Z i n c (I I) Io n s in N ,N -D im e th y la c e ta m id e Dedicated to Prof. Dr. Ohtaki on his occasion of 60th birthday The complexation of manganese (II), cobalt (II) and zinc(II) with thiocyanate ions has been studied in N,N-dimethylacetamide (DMA) by calorimetry and spectrophotometry at 298 K. In these metal systems the formation of a series of four isothiocyanato complexes, [M(NCS)J<2-n)+ (n = 1-^4; M = Mn, Co, and Zn) was established, and their formation constants, enthalpies and entropies were determined. Interestingly, the complexation behavior in DMA is significantly different from that in N,N-dimethylformamide (DMF), despite of the similarity of the physicochemical properties of these solvents. The complexation is indeed enhanced significantly in DMA over DMF and is more exothermic in the former solvent. Furthermore, with cobalt(II) an octahedral to tetrahedral coordi­ nation geometry change was found to occur in DMA at an earlier step of complexation than in DMF. These results suggest that six-coordination of DMA molecules to a metal ion is severely sterically hindered. 
  Reference    Z. Naturforsch. 50a, 11—17 (1995); received September 26 1994 
  Published    1995 
  Keywords    Thiocyanato complexes, Transition metal(II) ions, N, N-dimethylacetamide, Calorime­ try, Spectrophotometry 
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 TEI-XML for    default:Reihe_A/50/ZNA-1995-50a-0011.pdf 
 Identifier    ZNA-1995-50a-0011 
 Volume    50