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1999 (1)
1Author    Isabel Díaza, Vicente Fernández3, VitalyK. Belskyb, Jose Luis, M. Artínez0Requires cookie*
 Title    Synthesis and Structural Study of the Thermochromic Compounds Bis(2-amino-4-oxo-6-methylpyrimidinium) Tetrachlorocuprate(II) and Bis(2-amino-4-chloro-6-methylpyrimidinium) Hexachlorodicuprate(II)  
 Abstract    The compound bis(2-am ino-4-oxo-6-methylpyrimidinium) tetrachlorocuprate(II) 1 contains CuCU2-square-planar anions, and bis(2-am ino-4-chloro-6-m ethylpyrim idinium) hexachlorod-icuprate(II) 2 quasi-planar CU2CI62-anions. Both compounds show thermochromic behaviour. This phenomenon has been studied by X-ray crystallography at variable temperature, with the result that no major change is observed in the geometry o f the copper atom. Thus it is possible to assume som e influence o f the hydrogen bonds and o f the different geometries o f interme­ diate states on the color o f the compounds due to the modifications provoked in the L —>M charge transfer and in the energy o f the metal d-d transitions. Magnetic measurements o f the compounds give information on magneto-structural correlations. Compound 1 is ferromagnetic (Tc = 20 K) due to the perpendicular arrangement o f the square anions that allows exchange pathways only via Cu-Cl -Cu , H-bonding or cationic n electron interactions. Compound 2 shows a very complicated behavior at low temperature with local antiferromagnetic fluctua­ tions. Crystal data: 1 CioHioNftC^CUCu, triclinic, P i; 393(2) K: a = 11.053(2), b = 11.334(2), c = 14.038(3) (Ä), a = 95.76(3), ß = 101.35(3), 7 = 9 0 .1 5 (3) 0 ; 293(2) K: a = 11.022(2), b = 11.289(2), c = 14.001(3) (A), a = 95.86(2), ß = 101.34(2), 7 = 9 0 .0 9 (3) 0 ; 155(2) K: a = 11.008(2), b = 11.231 (2), c = 13.967(3) (A), a = 95.86(2), ß = 101.37(2), 7 = 8 9 .9 9 (2) 0 ; Z = 4. 2 (C5H7N 3C l3Cu)2, monoclinic, P 2,/c; 293(2) K: a = 5.998(1), b =18.669(4), c = 9.466(2) (A), ß = 1 0 0 .9 3 (3)0 ; 150(2) K: a = 5.971(1), b = 18.655(4), c = 9.3 8 3 (2) (Ä), ß = 1 0 1 .6 4 (1) 0 ; Z = 4. 
  Reference    Z. Naturforsch. 54b, 718 (1999); received March 1 1999 
  Published    1999 
  Keywords    Thermochromic Compounds, Copper, Chloride 
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 TEI-XML for    default:Reihe_B/54/ZNB-1999-54b-0718.pdf 
 Identifier    ZNB-1999-54b-0718 
 Volume    54