Catalytic Synthesis and Characterization of Biodegradable ...

Chapter 2
Figure 2.1 Crystal structure of the L 1 -Co III -dnp complex.
The geometry around the cobalt atom was octahedral with an almost linear axial
O(2)–Co(1)–O(4) bond angle of 177.52(7)º, and nearly perpendicular for O(1)–Co(1)–O(3),
O(3)–Co(1)–N(2), N(2)–Co(1)–N(1) and N(1)–Co(1)–O(1) of 88.03(7)º, 94.96(8)º, 83.29(8)º,
and 93.71(7)º, respectively, for the equatorial donor atoms. The Co(1) atom deviated from the
N(1)N(2)O(1)O(3) least-squares plane by only 0.0276 Å, representing the nearly ideal
octahedral arrangement. The distances from the Co atom to the O(1), O(2), O(3), O(4), N(1)
and N(2) atoms were 1.8969(15), 1.8868(15), 1.8964(16), 1.9672(16), 1.8985(18) and
1.902(18) Å, respectively (Table 2.1). Interestingly, the phenolate oxygen, O(3), is involved in
the equatorial planed rather than the four donor atoms in the tetradentate Schiff-base ligand.
Table 2.1 Selected bond distances and angles for L 1 -Co III -dnp.
Bond Distance(Å) Bond Angle(º) Bond Angle(º)
Co-N(1) 1.8985(18) O(1)-Co-O(2) 92.54(7) O(1)-Co-N(2) 176.99(7)
Co-O(1) 1.8969(15) O(1)-Co-N(1) 93.71(7) O(2)-Co-N(1) 96.37(7)
Co-O(3) 1.8964(16) N(2)-Co-N(1) 83.29(3) O(1)-Co-O(3) 88.03(7)
Co-N(2) 1.9020(18) O(2)-Co-O(3) 86.58(6) N(2)-Co-O(3) 94.96(8)
Co-O(2) 1.8868(15) N(1)-Co-O(3) 176.50(7) O(1)-Co-O(4) 87.41(7)
Co-O(4) 1.9672(16) O(2)-Co-O(4) 177.52(7) N(2)-Co-O(4) 92.16(7)
N(1)-Co-O(4) 86.11(7) O(3)-Co-O(4) 90.93(7)
O(2)-Co-N(2) 88.03(7)
The IR spectral data of the ligands and the complexes in Table 2.2 showed major bands
around 1624 cm -1 assigned to the C=N stretching vibration (vC=N), and around 1610 cm -1 and
1525 cm -1 assigned to the ring vibrations. The peaks around 1566 cm -1 and 1327 cm -1 were
assigned to the stretching of the N=O bonds, and the peaks around 1252 cm -1 and 1063 cm -1
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