540
M. Gaber et al. / Spectrochimica Acta Part A 69 (2008) 534–541
Fig. 4. HOMO–LUMO representation (bottom and top, respectively).
Scheme 2. Suggested structures of Co(II), Ni(II) and Cu(II) complexes.
ton of the HL are collected in Table 6. The values of bond order,
calculated after ground state geometry optimization, are consis-
tent with the expected ones and indicate the existence of a weak
H-bond between N10 and H27 (bond order is 0.0077). The ground
1.3 D indicating some charge transfer interaction between the
phenolic group as an electron donor and the pyrimidine one as
an acceptor, via the azo-bridge. Further confirmation for this fact
comes from charge density calculations, Table 6, where it was
found that the charge density on the azo-pyrimidine and phenolic
moieties are −0.1477 and +0.1478 e, respectively. In addition,
the calculations indicate different electronic transitions from
which the –* transition at 336 nm (oscillator strength = 0.65)
which corresponds to the HOMO–LUMO transition, is in agree-
ment with the experimental results (the absorption maximum in
n-heptane is 340 nm). This transition is well represented by plot
of the HOMO (at −0.3423 eV) and LUMO (at −0.0459 eV)
molecular orbitals as illustrated in Fig. 4.
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4. Conclusions
A new hydroxy azopyrimidine ligand and its Co(II), Ni(II)
and Cu(II) complexes have been synthesised and characterized
by combination of elemental analyses, spectral, magnetic, con-
ductance measurements, thermal and theoretical methods. From
the analytical and spectral data, it is concluded that the title
azodye acts as monobasic bidentate ligand with azo-nitrogen
and phenolic oxygen atoms. The spectral and magnetic data
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square planar for Cu(II) complexes. The thermal decomposi-
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Based on the above results, the structures of the complexes
are represented as given in Scheme 2.