## 3 Results and Discussion
### Characterization of Metal Complexes
The coordination mode of this ambidentate ligand depends on the stereochemical environment around the metal ions. In the FT-IR spectra of **CoL\({}_{1}\)** and **CoL\({}_{4}\)** complexes the characteristic band in 492 and 614 cm\({}^{-1}\) is observed which is due to the cobalt-oxygen stretching band; indicating the formation of nitrito isomer. The proposed structure for **CoL\({}_{1}\)** and **CoL\({}_{4}\)** complexes is given in Figure 2. The band due to v(C=N) in ligands were shifted to a lower wavenumbers in complexes which indicated the involvement of azomethine group in the coordination to the cobalt center. Also the bands in the range of 1583-1592 cm\({}^{-1}\) and 1328-1368 cm\({}^{-1}\) are assigned to the NO\({}_{2}\) groups. In the electronic spectra of **CoL\({}_{1}\)** and **CoL\({}_{4}\)** complexes the peaks in the range of 600-690 nm are associated with d-d transition; and the low intensity of these peaks indicated the symmetrical structure of these complexes. The mass spectra of these complexes were recorded at room temperature to confirm the stoichiometry of metal chelates as studied above. The molecular ion peak for the **CoL\({}_{1}\)** and **CoL\({}_{4}\)** complexes were observed at \(m/z=633\) and 573, respectively that are equal to the molecular weight of the complexes. Figure 3 shows the proposed structure for **CoL\({}_{2}\)** and **CoL\({}_{5}\)** complexes. In FTIR spectra of **CoL\({}_{2}\)** and **CoL\({}_{5}\)** complexes containing the OMe substituent the (C-H) aliphatic functional groups appeared in the range of 2840-2900 cm\({}^{-1}\) while the C=NH bands are observed in the range of 1619-1626 cm\({}^{-1}\). The peaks in the range of 474-511 cm\({}^{-1}\) are assigned to the M-O band. The electronic absorption spectrum of **CoL\({}_{2}\)** and **CoL\({}_{5}\)** complexes showed four peaks. The first and second peaks are due to the n\(\rightarrow\)n\({}^{*}\) and n\(\rightarrow\)n\({}^{*}\) transition of ligand group which shifted to higher wavelength compared to free ligand. The d-d transition bands are observed in the range 590-610 and 660-680 nm owing to \({}^{4}\)A\({}_{1}\)\(\rightarrow\)\({}^{4}\)B\({}_{1}\) and \({}^{4}\)A\({}_{1}\)\(\rightarrow\)\({}^{4}\)B\({}_{2}\) transitions. The mass spectra of **CoL\({}_{2}\)** and **CoL\({}_{5}\)** are in good agreement with the proposed structures. The mass spectra of **CoL\({}_{2}\)** and **CoL\({}_{5}\)** complexes showed molecular ion peak at \(m/z=603\) and 473, respectively, confirming their formula weight. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Compounds** & **M. W. (g/mol)** & **Yield (\%)** & **Color** & **Molar Conductivity (\(\Omega^{-1}\) mol\({}^{-1}\) cm\({}^{2}\))** & **M. P. (\({}^{5}\)C)** \\ \hline
**L\({}_{1}\)** & 374 & 84 & Dark yellow & - & 208–210 \\
**L\({}_{2}\)** & 344 & 86 & Orange & - & 190–192 \\
**L\({}_{3}\)** & 316 & 64 & Brown & - & 295–297 \\
**L\({}_{4}\)** & 254 & 68 & Yellow & - & 203–205 \\
**L\({}_{5}\)** & 239 & 73 & Pale Yellow & - & 181–183 \\
**L\({}_{6}\)** & 225 & 65 & Light green & - & 282–284 \\
**CoL\({}_{4}\)** & 633 & 65 & Pale green & 22 & 284–250 \\
**CoL\({}_{2}\)** & 603 & 68 & Dark green & 12 & 313–315 \\
**CoL\({}_{3}\)** & 575 & 75 & Dark brown & 14 & 230–232 \\
**CoL\({}_{4}\)** & 503 & 80 & Green & 18 & 280–28 \\
**CoL\({}_{5}\)** & 473 & 82 & Orange-red & 16 & 305–307 \\
**CoL\({}_{6}\)** & 445 & 87 & Dark-pink & 10 & 236–238 \\ \hline \end{tabular}
\end{table} 
Table 4: Physical properties of synthesized compounds. M. W.: molecular weight; M. P.: melting point. Figure 2: Proposed structure for **CoL\({}_{1}\)** and **CoL\({}_{4}\)** complexes. In the FTIR spectra of **CoL\({}_{3}\)** and **CoL\({}_{6}\)** complexes the stretching frequency of C=N are observed at 1650 and 1634 cm\({}^{-1}\), respectively. The disappearance of OH groups in **CoL\({}_{3}\)** and **CoL\({}_{6}\)** complexes indicate the OH group of ligands has been deprotonated and coordinate to metal ions.