The ligands and their metal complexes were screened in vitro for their antibacterial potencies against gram positive and gram negative bacteria (Escherichia coli, Serratia mercescens, Salmonella tyhi, Shigella flexneri and Staphylococcus aereus) and fungi (Trichoderma viride, Monilia albicans, Saccharomycodes ludwigii, Rhizopus stolon and Mucor mucedo). These compounds were dissolved in DMSO. Two-eight hour old bacterial inoculums containing approximately 10⁴ - 10⁶ colony forming units (CFU/ml) were used. Wells of 0.8 mm in diameter

were dug in the media with the aid of a sterile metallic cork borer. The test organisms were inoculated into disposable plates, each well bored at four equidistant peripheral points and inoculation was repeated three times. The wells were filled with 1 mg/ml and 10 μg/ml for bacteria and fungi respectively of the complex solutions. DMSO and reference antibacterial and antifungal drugs (tetracycline and amphotericin respectively) were used as standard drugs. The organisms were grown on Meuller Hinton and potato dextrose (Agar) for bacteria and fungi respectively at 37˚C for 48 hours (bacteria) and at 30˚C for seven days (fungi).

Electro Thermal Digital melting point apparatus was used to obtain the melting points of the ligands and TMCs. The percentage yields values of the ligands and TMCs were relatively high (76% - 92%). The melting points showed that the compounds are stable in solid states (Table 1). The ligands were soluble in water, polar organic solvents and sparingly soluble in non-polar organic solvents. The TMCs were insoluble in water, but soluble in most organic solvents (Table 2). The solubility test suggests that the synthesized compounds are non-polar.

The results of the FTIR spectroscopy (Table 3) showed absorption peaks for the ligands and the TMCs for v(C-N) at range 1488 - 1489 cm⁻¹. v(C-S) at range 931 - 997 cm⁻¹, the single band at this region is related to the bidentate coordination as revealed by previous researchers (Mcelwa, 2013), v(N-H) at range 3143 - 3440 cm⁻¹. The most important absorption at 600 - 900 cm⁻¹ as observed in related works (Sunitha et al., 2011) is the most important one resulting from the out of plane bending vibration. 720 cm⁻¹ was observed for v(=C-H) bending modes of the aromatic ring (p-chlorophenyl dithiocarbamate) while 820 cm⁻¹ was observed for that of (p-bromophenyl dithiocarbamate).

The electronic spectra of the ligands and TMCs were recorded in DMSO using a Lamda Perkin Spectrometer. Zn (II) absorbed at around (244, 299 and 340 nm), Cd (II) at (268 and 328 nm), Hg (II) at (243 and 320 nm), Cu (II) at [261, 320, both due to intra ligand charge transfer and 402 (d-d transition) nm], Co (II) at [245, 323, both due to intra ligand charge transfer, 388 (metal to ligand charge transfer), 620 (d-d transition) nm] and Ni (II) at [(254 and 326), due to intraligand charge transfer, (386 and 435, medium bands due to metal to ligand charge transfer), (490 and 640, weak bands due to d-d transition) nm]. The transitions in Zn (II), Cd (II), Hg (II) are due to intraligand charge transfer and metal to ligand charge transfer.

The antimicrobial activity of the ligands and TMCs were investigated in vitro against some selected bacteria such as Escherichia coli, Serratia mercescens and Staphylococcus aereus. From Table 4 and Table 5, they showed good activity against the bacterial infections, with Cd (II), Hg (II), Co (II) and Cu (II) showing better activities than the ligands and standard drug. The TMCs were poor against the fungal infections.

NB: MIC of standard antibacterial drug (tetracycline) = 0.25 mg/ml while antifungal drug (amphoterin B) is 2.5 μg/ml.