**3. Results and discussion**

*Solvents, Ionic Liquids and Solvent Effects*

for [C28H32NiN8O6]

**Figure 1.**

*m/z*) [M-2BF4]

N 13.46, Cu 7.61.

**2.4 Antibacterial assay**

*2.3.3 Cu(II) complex (5a)*

+

of bacterial suspension containing 108

the mean values were accepted.

+

UV/vis (methanol, λmax/nm): 220, 340, 400. ESI-MS (CH3OH, *m/z*) [M-2BF4]

*Synthesis of Ionic liquid supported Schiff base (2a) and its metal complexes 3a, 4a and 5a from 2a.*

Dark green solid; (0.57 g, 70%), decomposes at ~295°C. IR (KBr): ʋ = 3429 (O▬H), 1656 (C═N), 1334 (N▬O), 1175 (C▬O), 1103 (B▬F), 633 (M▬O), 471 (M▬N). UV/vis (methanol, λmax/nm): 226, 244, 354. ESI-MS (CH3OH,

+

C28H36CuB2F8N8O8 (813.76): C 41.33, H 3.96, N 13.77, Cu 7.81, found: C 41.12, H 3.61,

The synthesized ligand (**2a**) and complexes (**3a**, **4a** and **5a**) were screened against the Gram-negative bacteria (*E. coli*, *P. aeruginosa*, *P. vulgaris* and *E. aerogenes*) and Gram-positive bacteria (*S. aureus* and *B. cereus*) strains. The tests were performed using agar disc diffusion method [26]. The nutrient agar (Hi-Media Laboratories Limited, Mumbai, India) was put in an autoclave at 121°C and 1 atm for 15–20 min. The sterile nutrient medium was kept at 45–50°C and then 100 μL

with sterile liquid nutrient agar and poured into the sterile Petri dishes. All the stock solutions were made by dissolving the compounds in dimethylsulfoxide (DMSO). The concentrations of the tested compounds were 10, 20, 30, 40 and 50 μg/mL. The tested microorganisms were grown on nutrient agar medium in Petri dishes. The samples were soaked in a filter paper disc of 1 mm thickness and 5 mm diameter. The discs were kept on Petri plates and incubated for 24 h at 37°C. The diameter of the inhibition zone (including disc diameter of 5 mm) was measured. Each experiment was carried out three times to minimize the error and

H 3.99, N 13.85, Ni 7.26, found: C 41.22, H 3.63, N 13.46, Ni 7.11.

calcd. for [C28H32CuN8O6]

: 634, found: 634; anal. calcd. for C28H36NiB2F8N8O8 (809): C 41.57,

: 634, found: 634. Anal. calcd. for

colony-forming units (CFU)/mL was mixed

+ calcd.

**84**

All the isolated compounds were stable at room temperature to be characterized by different analytical and spectroscopic methods. The complexes are soluble in *N*,*N*-dimethylformamide, dimethylsulfoxide, acetonitrile, methanol and water.
