Nickel complexed within an azamacrocycle as a structure directing agent in the crystallisation of the framework metalloaluminophosphates STA-6 and STA-7

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Abstract

Nickel complexed with the azamacrocycle 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane (tmtact) acts to direct the crystallisation of metalloaluminophosphate (MAPO, M = Mg, Mn, Co, Zn) and silicoaluminophosphate (SAPO) gels to an orthorhombic variant of the STA-6 material (structure code SAS) and to mixtures of this phase with STA-7 (structure code SAV). Compositional analysis, diffuse reflectance UV-visible spectroscopy, magnetic susceptibility and solid state NMR of pure STA-6 samples show that the nickel remains complexed within the macrocycle after crystallisation, adopting square planar geometry. The positive charge on the divalent complex is balanced by the negative charge imparted to the framework by the aliovalent substitution of divalent cations for aluminium or the incorporation of silicon for phosphorus. Crystallographic analysis of a single crystal of the Ni(tmtact)-CoAPO form of STA-7 (P4/n, a = 18.684(1) Angstrom, c = 9.408(1) Angstrom) is able to locate the complex, disordered about the 4-fold axis, within supercages in the structure. The inorganic framework of the Ni(tmtact)(2+)-templated STA-6 solids remains intact as the organics are removed by calcination, and the STA-6 becomes tetragonal. The paramagnetic Ni2+ cations are left within the pore structure. Reduction of the calcined sample in hydrogen at temperatures of 473-523 K gives Ni(I), as shown by ESR spectroscopy, g = 2.09.

Original languageEnglish
Pages (from-to)1421-1427
Number of pages7
JournalJournal of Materials Chemistry
Volume11
Publication statusPublished - 2001

Keywords

  • Azamacrocycle
  • Structure-directing agent
  • Aluminophosphate
  • SURFACE COMPLEXES
  • MOLECULAR-SIEVES
  • CHIRAL LAYERS
  • ALUMINOPHOSPHATE
  • IONS
  • SILICA
  • CYCLOTRIMERIZATION
  • 5-CO-ORDINATE
  • PHOSPHATES
  • ACETYLENE

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