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Keywords:

  • Cadmium borate;
  • Solvothermal synthesis;
  • Crystal structure;
  • Hydrogen bonds;
  • Thermal analysis

Abstract

Two new cadmium borates, [Cd(en)3][B5O6(OH)4]2·2H2O (en = ethylenediamine) (1) and [Cd(DETA)2][B5O6(OH)4]2 (DETA = diethylenetriamine) (2) were synthesized in a novel procedure under mild solvothermal conditions and characterized by single-crystal X-ray diffraction, IR spectroscopy, elemental analysis, and TG–DTA. The compound 1 crystallizes in monoclinic system, space group P21/c (No. 14) with a = 8.526(2) Å, b = 23.127(6) Å, c = 15.438(4) Å, β = 94.320(3) °, V = 3035.5(13) Å3, Z = 4. Compound 2 is triclinic, space group Pequation image (No. 2), a = 8.632(5) Å, b = 9.418(6) Å, c = 27.856(18) Å, α = 95.415(8) °, β = 91.891(7) °, γ = 93.563 (7) °, V = 2248(2) Å3, Z = 3. The anionic units of the both structures, [B5O6(OH)4] are linked by hydrogen bonds to form a three-dimensional framework with large channels, in which the templating cadmium complex cations are located. The thermal decomposition performance of compound 1 requires three steps, whereas only two steps are needed for compound 2, which all lead to amorphous phases. These processes are well explained considering the structure and the change in the Cd2+ coordination during heating.