The insertion of Al(III) cation into a poly(8-
Hydroxyquinoline) (PHQ) instead of some metal ions such
as Co(II), Ni(II), Zn(II) or Fe(III) ions via cation-exchange
mechanism has been studied by several techniques. The
presence of Al(III) and the absence of Co(II) cations has
been proved by elemental analysis of the polymer chelates
product. Molecular mechanics (MM?) calculations
showed that the potential energy (PE, kJ mol-1) of the
optimum molecular geometric structure (OMG) of the
PHQ–Al(III) matrix is about seventy-six (76.185) greater
than the PE of the PHQ–Co(II) complex. The TGA thermograms
show that the PHQ–Al(III) matrix is thermally
unstable than the PHQ–Co(II) complex under the same conditions. These observations indicate that the PHQ–Al(III) is expanded coil-like form. So, the thermal decomposition of PHQ–Al(III) complex is easy than the compacted coil-likes form of PHQ–Co(II) complex. The incorporation of Al(III) ion via cation-exchange properties
have been investigated by spectrophotometric technique. The decrease of the absorbance at about *370 nm of PHQ–Co(II) complex associated with increasing concentration of Al(III) revealed the replacement of that metal ion by Al(III) into PHQ chain. The cation-exchange constant(Kex) of the divalent ions [Ni(II), Co(II), Cr(II), Zn(II),
Mn(II), Mg(II) and Cu(II)] from PHQ–M(II) by the additions of Al(III) according to the following series: Ni(II)[Co(II)[Cr(II)[Cu(II)[Zn(II)[Mn(II)[Mg(II).