**3.5 Electronic spectra and magnetic moment**

*Solvents, Ionic Liquids and Solvent Effects*

**90**

**Figure 13.**

**Figure 12.**

*PXRD spectra of Co(II) complex (3a).*

**3.4 Mass spectral studies**

*PXRD spectra of Ni(II) complex (4a).*

at 634 (M = [C28H32NiN8O6]

at m/z 289, that corresponds to [M-BF4]

+

To get information regarding the structure of the synthesized compounds at the molecular level, electrospray ionization (ESI) mass spectrometry was performed using methanol as solvent. Mass-spectra of the LH (**2a**) had a molecular ion peaks

) and at 639 (M = [C28H32CuN8O6]

, [M = C14H17N4O2]

+

+

. The metal complexes

) which confirmed

+ ),

+

(**3a, 4a** and **5a**) exhibited molecular ion peaks (*m/z*) at 635 (M = [C28H32CoN8O6]

The UV-visible spectra of the Schiff base and its metal complexes (as depicted in **Figure 15**) were recorded at room temperature using methanol as solvent.

**Figure 14.** *PXRD spectra of Cu(II) complex (5a).*

**Figure 15.**

*UV-visible spectra in methanol (concentration of the solutions 1 × 10–4 M): (A) LH (2a); (B) Co(II) complex (3a); (C) Ni(II) complex (4a) and (D) Cu(II) complex (5a).*

The LH (**2a**) exhibited three absorption bands at 306, 234 and 206 nm due to n → π\*, π → π\* and transitions involved with the imidazolium moiety, respectively [37, 38]. For the complexes, the bands that appeared below 350 nm were ligand centered transitions (n → π\* and π → π\*). The Co(II) complex (**3a**) displayed a band at 354 nm which could be attributed to the combination of <sup>2</sup> B1g → <sup>1</sup> A1g and <sup>1</sup> B1g → <sup>2</sup> Eg transitions and supporting square planar geometry [39, 40]. The complex (**3a**) showed magnetic moment of 2.30 B.M. due to one unpaired electron. The Ni(II) complex (**4a**) was diamagnetic and the band appeared at around 400 nm due to <sup>1</sup> A1g → <sup>1</sup> B1g transition is consistent with low spin square planar environment [41]. UV-visible spectra of Cu(II) complex (**5a**) exhibited d → π\* metal-ligand charge transfer transition (MLCT) at the region 358 nm had been assigned to the combination of <sup>2</sup> B1g → <sup>2</sup> Eg and <sup>2</sup> B1g → <sup>2</sup> B2g transitions in a distorted square planar geometry. The experimental magnetic moment value for **5a** was 1.84 B.M. consistent with the presence of an unpaired electron [42, 43].
