ISSN:
1572-9001
Schlagwort(e):
Quasi-two-dimensional metamagnet
;
differential scanning calorimetry
Quelle:
Springer Online Journal Archives 1860-2000
Thema:
Chemie und Pharmazie
Notizen:
Abstract [C6H22N4]4+[CuCl4 2−]Cl2 (I) crystallizes in the monoclinic space groupP21/c with cell constantsa=15.573(2) Å,b=7.281(2),c=7.092(2),β=91.496(14)°,V= 803.874 Å3, andd(z= 2 mol/cell)=1.762 gm cm−3. Data were collected in the range 4° ≤ 2θ ≤ 50°, for a total of 2662 reflections, of which 2201 were independent and hadI ≽ 3σ(I). These were used in the solution and refinement of the structure. TheF(hkl) obs were corrected for absorption (μ=23.558 cm−1) using Psi scan curves of eight suitable reflections, leading to relative transmission coefficient adjustments ranging from 0.9999 to 0.5722. Structural refinement converged atR(F)= 0.023 and R W (F)=0.026. The coordination around the metal consists of polymeric, axially elongated, six-bonded, trigonal antiprismatic CuCl6 species, not the hoped for, discrete, molecular CuCl6 4− species implied by their chemical formulation. The crystalline lattice contains three different types of ions: the (C6H22N4)4+ cation, a pair of Cl− anions which are hydrogen bonded to the secondary ammonium (-NH2 +-) hydrogens of the cation, and a CuCl4 2− anion. The latter is polymerized into two-dimensional sheets linked to each other by the agency of the cations, in which the two sets of terminal (-NH3 +) hydrogen bond to the axial Cl− ligands. The Cu-Cl distances are 2.279, 2.315, and 2.847 Å. The distance between nearest coppers in adjacent sheets is 15.573(2)Å, the length of thea-axis. The magnetic behavior of the compound is that of a metamagnet, which requires a somewhat unusual set of conditions and is very rare in Cu2+ compounds. Comparison of the magnetic behavior of (I) with that of related compounds is made. The thermal behavior of (I) was studied using differential scanning calorimetric measurements in the range of 120 K to its melting(dec) point (463 K). It undergoes a phase transition from green (low temperature phase) to golden yellow (room temperature phase) at 168 K, another phase transition (golden yellow to red) at 340.6 K, and another at 383.2 K during which there is not evident color change. Finally, it melts with decomposition at ca. 463 K.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1007/BF00672097
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