Co(II) and Fe(II) mixed ligand complexes of Pefloxacin and Ascorbic acid: Synthesis, Characterization and Antibacterial Studies

Onyenze U.¹, Otuokere I.E.¹, Igwe J. C.²

¹Department of Chemistry, Michael Okpara University of Agriculture, Umudike, Umuahia, Abia State, Nigeria

²Department of Pure and Industrial Chemistry, Abia State University, Uturu, Abia State, Nigeria

*Corresponding Author E-mail: ifeanyiotuokere@gmail.com

Abstract:

Mixed ligand metal complexes of 1-ethyl-6-fluoro-7-(4-methylpiperazin-1-yl)-4-oxo-quinoline-3-carboxylic acid (pefloxacin) and ascorbic acid were synthesized using Fe(II) and Co(II). The mixed ligand complexes were characterized by IR, UV-Vis., ¹H and ¹³C NMR spectroscopy to determine the complexation behaviour of the metal ions towards the mixed ligand. The yield, melting point, colour and solubility were determined. Electronic spectra of the mixed ligand complexes show intra ligand charge transfer, ligand to metal charge transfer and d-d transition. Based on the spectroscopic data obtained, the mixed complexes were proposed to have the formulae: [Fe(PfAs)]_x and [Co(PfAs)]; Pf = pefloxacin and As = Ascorbic acid. The spectral studies of the mixed ligand complexes suggest that in the complexes, pefloxacin and ascorbic acid behaved as tridentate ligands coordinating through the two carbonyl oxygen atom and oxygen atom of the hydroxyl group in pefloxacin, while ascorbic acid coordinated through the oxygen of the carbonyl and enolic C-2 and C-3 hydroxyl groups. Octahedral structure was proposed for [Fe(PfAs)]_x and [Co(PfAs)]_x. The antibacterial activity of the ligand and the mixed ligand complexes was carried out against both gram positive and gram negative bacterial species which include; Staphylococcus aureus, E. coli., Bacillus subtilis, Pseudominas Spp. and Candida Spp. at 0.1g. The zone of inhibition of the pefloxacin-ascorbic acid mixed ligand complexes were significantly higher (P < 0.05) than the free ligands.

KEY WORDS: Pefloxacin, synthesis, mixed ligand, complexes, antibacterial.

Introduction:

Life – threatening conditions have been easily curable and the incidence of death or disability resulting from bacterial infections has been greatly reduced since the introduction of effective antibacterial therapies for infectious diseases. The introduction of metal ions into chemotherapy agents with the aim of increasing their efficacy has been an extensive research area for more than three decades since the discovery of Cis-platin ^1,2.

Metal ions can be toxic or add to the health of the organism depending on the concentration of the metal and they play very significant roles in widely differing biological processes and affect the well-being of human in various ways.

Mixed ligand or antibiotic metal complexes of transition metals are gaining recognition due to their efficacy against the parent drugs used ^3,4. The stabilities of mixed chelates are of great importance in biological systems as many metabolic and toxicological functions are dependent upon this stability ⁵. In the search for novel metal complexes, that combine high activity with low toxicity, the study of metal complexes has continued to attract attention of some coordination chemists^6,7. An extensive work has been carried out by inorganic chemists on characterization, antimicrobial and toxicological activity of mixed ligand complexes of transition metals and actinide metal ions^8-12. Thus, the search for new anti-antibacterial therapies to combat bacterial diseases is of high priority. In continuation of our search for new chemotherapy agents, we synthesize novel mixed metal complexes of pefloxacin mixed with ascorbic acid with a view to examine their antibacterial efficacy against the parent drugs.

MATERIAL AND METHODS:

All chemicals used in this study were of analytical grade and were used without further purification. Pefloxacin, and ascorbic acid were received from Mancare pharmaceuticals PVT. LTD. India. Iron (II) sulphate heptahydrate and Cobalt (II) sulphate were purchased from Loba Chemie limited Mumbai 400005, India. The electronic spectra of the mixed ligand complexes were recorded on UV/Visible spectrophotometer (UV-2500PC series) at wavelength range of 200 – 800nm. The samples were dissolved in dimethylsulphoxide (DMSO). Fourier transform infrared (FT-IR) spectra were recorded on Shimadzu FTIR 8400S model Spectrophotometer in the range 4000 – 400 cm^-1 using KBr pellets. The proton and carbon -13 NMR spectra were recorded on a JEOL JNM-EX 270 spectrometer at 270.2 and 67.8 MHz. Deuterated dimethylsulfoxide (DMSO – d₆) was used as solvents. The procedure described in literature^13,14 was used to synthesize the complexes, with slight modification. The melting point of the ligands and the mixed ligand complexes were determined using open capillary tube method. The solubilities of the mixed ligand complexes were determined in different solvents ranging from polar to non-polar solvents such as distilled water, methanol, DMSO, chloroform acetone and petroleum ether.

Synthesis of mixed ligand complexes of pefloxacin and ascorbic acid

8.34g (30mmol) and 4.65g (30mmol) of the metal salts (FeSO₄.7H₂O and CoSO₄ respectively) were dissolved in 50ml of methanol, followed by addition of 10g of pefloxacin and 5.28g (30mmol) of ascorbic acid with constant stirring. The solutions was refluxed for 3 hours, transferred to a beaker and allowed to cool for 30 minutes. The precipitate was dried in a desiccator over calcium chloride for three days. The product was labeled for analysis/characterization.

Antibacterial studies

Antibacterial activities of the parent drugs and the mixed ligand complexes were tested against five different species of bacteria, namely: Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Pseudomonas Spp, and Candida Spp. Nutrient agar was used as the bacteriological growth media. The bacterial activities in the presence of both the parent drug and the mixed ligand complexes were determined by filter paper disc agar diffusion method ¹⁵. The antibacterial activity of the compounds was estimated on the basis of the size of the inhibition zone formed around the wells on the seeded nutrient agar.

RESULTS AND DISCUSSION:

Physical properties of pefloxacin, ascorbic acid and their mixed ligand complexes are presented in Table 1. Solubility data of pefloxacin, ascorbic acid and their mixed ligand complexes are shown in Table 2. Selected IR, electronic ¹H NMR and ¹³C NMR spectral data of pefloxacin, ascorbic acid and their mixed ligand complexes are shown in Tables 3, 4, 6 and 7. Crystal field splitting energy, Racah parameter and Nephelauxetic effects of the mixed ligand complexes have been reported in Table 5. The zones of inhibition (mm) of pefloxacin, ascorbic acid and their mixed ligand complexes against some selected microorganism are reported in Table 8 while the minimum inhibitory concentrations of pefloxacin and its mixed ligand complexes against some selected microorganisms are shown in Table 9.

Table 1: Some physical properties of pefloxacin, ascorbic acid and their mixed ligand complexes

Ligand/ Complexes	Colour	Melting Point (^OC)	Yield (%)
Pefloxacin	White	271	-
Ascobic Acid	White	190	-
[Fe(PfAs)]x	Deep brown	> 300	11.89
[Co(PfAs)]x	Brown	> 300	18.61

Pf = Pefloxacin, As = Ascorbic acid

Table 2: Solubility data of pefloxacin, ascorbic acid and their mixed ligand complexes

Ligand/ Complexes	Distilled water	DMSO	Methanol	Chloroform	Acetone	Petroleum ether
Pefloxacin	SS	S	S	SS	NS	NS
Ascobic Acid	S	S	SS	NS	NS	NS
[Fe(PfAs)]x	NS	S	NS	NS	NS	NS
[Co(PfAs)]x	S	S	NS	NS	NS	NS

NB: Ѕ = Soluble, SS = Slightly Soluble, NS = Not soluble, Pf = Pefloxacin, As = Ascorbic acid

Table 3: Selected IR Spectral data of pefloxacin, ascorbic acid and their mixed ligand complexes

Ligand/ Complexes	ν OH (cm^-1)	ν C-H (cm^-1)	ν C=O (cm^-1)	ν M-O (cm^-1)
Pefloxacin	3500.00 3429.34	2925.00	1625.00	-
Ascorbic Acid	3260.00 3520.00 3360.00	2922.10	1674.00	-
[Fe(PfAs)]x	3606.04	2931.90	1644.37	406.99
[Co(PfAs)]x	3360.11 3413.15 3439.19	2934.79	1686.81	465.82

Pf = Pefloxacin, As = Ascorbic acid

Table 4: Electronic spectral data of pefloxacin, ascorbic acid and their mixed ligand complexes

Ligand/ Complex	Wavelength (nm)	Energy (cm^-1)	Assignment
pefloxacin	288.51	34722.22	ILCT (π® π^*)
Ascorbic Acid	254.00	39370. 08	ILCT (π® π^*)
[Fe(PfAs)]x	785.00 320.50 274.00	12738.85 31201.25 36496.35	^5T2 ® ^5E LMCT ILCT
[Co(PfAs)]x	784.50 341.00 332.50	12746.97 29325.51 30075.19	^4T1(F) →^4T2(F) ^4T1(F) ®^4A2 LMCT

Pf = Pefloxacin, As = Ascorbic acid

Table 5: Crystal field splitting energy, Racah parameter and Nephelauxetic effects of the mixed ligand complexes

Complex	Dq (cm^-1)	B (cm^-1)	β	Dq/B	ν1/B	ν2/ν1
[Fe(PfAs)]x	-	-	-	-	-	-
[Co(PfAs)]x	11513	411.19	0.3671	28	31	2.30

Pf = Pefloxacin, As = Ascorbic acid

Table 6: ¹H NMR spectral data of pefloxacin, ascorbic acid and its complexes

Compound	Hydroxyl protons(ppm)	Methyl,  methylene protons(ppm)	Aromatic protons(ppm)
Pefloxacin	9.81	1.56, 2.25, 2.45, 3.06, 4.33	6.83, 7.93, 8.66
Ascorbic	2.84, 10.95, 11.02	3.64, 3.78,	-
[Fe(PfAs)]x	11.38, 12.73, 12.75	1.55, 2.27, 2.48, 2.91, 3.06	6.14, 6.66, 6.85, 7.62
[Co(PfAs)]x	11.40, 13.03, 13.16	1.53, 2.28, 2.46, 2.90, 3.07	6.13, 6.62, 6.88, 7.66

Pf = Pefloxacin, As = Ascorbic acid

Table 7: ¹³C NMR spectral data of pefloxacin, ascorbic acid and their mixed ligand complexes

Compound	C=O (ppm)	COOH (ppm)	Ar Carbons (ppm)	CH3 and CH2 (ppm)
Pefloxacin	175.82	165.62	106.40, 111.18, 119.82, 136.89, 143.61, 148.41, 152.42	14.41, 42.21, 49.03, 49.62, 54.93
Ascorbic	173.96	-	-	77.13, 69.91, 63.25, 156.25, 118.83
[Fe(PfAs)]x	187.22, 184.21	192.20	104.22, 111.82, 114.63, 119.45, 137.13, 143.52, 147.93, 153.34	14.20, 42.22, 49.22, 49.62, 54.93, 63.31, 70.33, 90.13
[Co(PfAs)]x	183.23, 185.20	188.27	104.29, 111.89, 114.62, 119.41, 137.12, 143.57, 147.91, 153.30	14.23, 42.26, 49.29, 49.67, 54.93, 63.31, 70.32, 90.18

Pf = Pefloxacin, As = Ascorbic acid

Table 8: The zones of inhibition (mm) of pefloxacin, ascorbic acid and the mixed ligand complexes against some selected microorganism

Compound	S. aureus	E. Coli	Bacillus subtilis	Pseudominas Spp.	Candida Spp.
Ascorbic acid Pefloxacin	NA 33.00^c ± 1.00	NA 43.33^b ± 0.58	NA 50.33^a ± 0.58	NA 50.57^b ± 0.06	NA 43.17^b ± 0.76
[Fe(PfAs)]x	48.57^a ± 0.40	37.00^c ± 0.10	50.67^a ± 0.58	50.73^b ± 0.64	37.00^c ± 1.00
[Co(PfAs)]x	36.07^b ± 0.11	60.03^a ± 0.06	38.00^b ± 1.00	59.00^a ± 1.00	49.00^a ± 1.00

Values are means ± standard deviation of triplicate determination.

a-c means bearing different superscripts in the same column are significantly different (P < 0.05) while means with the same superscript shows no significant difference (P > 0.05).

Pf = Pefloxacin, As = Ascorbic acid, NA = No Activity,

Table 9: The minimum inhibitory concentrations of pefloxacin and the mixed ligand complexes against some selected microorganisms

Compound	Conc. μg/ml	S. aureus	E.Coli	Bacillus subtilis	Pseudominas Spp.	Candida Spp.
Pefloxacin	0.1 0.05 0.025	- - +	- - +	- - +	- - +	- + +
[Fe(PfAs)]x	0.1 0.05 0.025	- - +	- - +	- - +	- - +	- + +
[Co(PfAs)]x	0.1 0.05 0.025	- + +	- - +	- + +	- - +	- + +

+ = Growth observed in medium; - = Absence of growth in medium

Pf = Pefloxacin, As = Ascorbic acid;

Table 1 showed the result of the physical properties of the free ligands and their mixed complexes. The mixed complexes are coloured. This means that there is absorption in the visible part of the spectrum resulting from an electron being excited by visible light from a level occupied by an electron in a molecular orbital of the complex to an empty level¹⁶. The colours are either due to d - d electron transitions or charge transfer from the ligand to the metal ion¹⁷. The mixed ligand complexes are of high melting points compared to the free ligand, this is in agreement to complexes reported¹⁸. The high melting point suggests the formation of the complexes ¹². The mixed complexes were found to be soluble in DMSO but insoluble in acetone, chloroform, distilled water and petroleum ether.

The infrared spectrum of the free ligands was compared with the infrared spectra of its complexes, in order to determine the point of coordination of the metal ions with the ligands. The spectra of all the complexes show similar bands due to the presence of the same ligands in all the complexes. In the infrared spectrum of the free ascorbic acid, vibrational frequencies at 3260 cm^-1, 3520 cm^-1 and 3360 cm^-1 were assigned to O–H stretching ¹⁹. The absorptions shifted in both Fe(II) and Co(II) complexes due to complexation. The IR spectrum of pefloxacin at 3500 cm^-1 also shifted in both the complexes. The bands at 1674 cm^-1 in ascorbic acid and 1625 cm^-1 in the free pefloxacin, were assigned to C=O stretching vibrations, these bands have shifted in the mixed complexes to 1644.37 cm^-1 and 1686.81 cm^-1 for Fe(II) and Co(II) complexes respectively. The band at 2925.00 cm^-1 and 2922.10 cm^-1 for C-H vibration did not show a significant shift in the complexes. This shows that coordination did not occur through this position. Also, the infrared spectra of the complexes exhibit strong bands at 406.99 cm^-1 and 465.82 cm^-1, they were attributed to M-O vibration²⁰. The bands was conspicuously absent in the spectra of the ligands. The appearance of M-O vibration further supports the involvement of oxygen in the complexation. Other bands observed in the spectra of the ligands were also observed in the metal complexes¹⁰.

The electronic spectral data of pefloxacin ligand showed a peak at 288.51 nm (34722.22 cm^-1) which has been assigned to π ® π* transition. The ascorbic acid ligand shows a peak at 254.00 nm (39370.00 cm^-1) and has been assigned to intra ligand charge transition. These transitions are as a result of chromosphores present in the ligands. The Fe(II) mixed complex showed absorption band at 320.50 nm (31201.25 cm^-1) which is due to ligand to metal charge transfer. The other band at 785.00 nm (12738.85 cm^-1) is assignable to ⁵T₂®⁵E transition which suggests an octahedral geometry ²¹. The electronic spectra of Co(II) mixed ligand complex exhibited three peaks at 332.50 nm (30075.19 cm^-1) which has been assigned to ligand to metal charge transfer (LMCT) and the other two appeared at 12746.97 and 29325.51 cm^-1 which are assignable to ⁴T₂(F) ® ⁴T₁(P) and ⁴T₂ ® ⁴A₂(F) transitions respectively in octahedral geometry²². The ⁴T₁®⁴T₂ and ⁴T₁®⁴A₂ transitions were used to calculate the ligand field parameter (Dq), the Racah parameter (B) and the nephelauxetic effect (β) using the Tanabe-Sugano diagrams.

The calculated value of the ligand field parameter, Dq is 11513.39 cm^-1 for (ν1). Thus, the interelectronic repulsion parameter or the Racah parameter B, was calculated and found to be 411 cm^-1 for Co(II) complex. Moreover, the nephelauxetic ratio β = B/B^O = 0.3671 (36.71%) indicates appreciable covalent character in this complex ^{21, 23, 24}. The reduction is a general observation and indicates that electron repulsions are weaker in complexes than in the free atoms and ions. The weakening occurs because the occupied molecular orbitals are delocalized over the ligands and away from the metal. The delocalization increased the average separation of the electrons and hence reduces their mutual repulsion^{21, 25}.

Comparison of the ¹H NMR of the mixed ligand complexes and the ligands (pefloxacin and ascorbic acid) were made in order to ascertain the points of coordination. The chemical shift of carboxylic OH group in pefloxacin appeared at 9.81. ppm while the OH group of ascorbic acid appeared at 10.95 and 11.02ppm respectively. In the spectrum of [Co(PfAs)]_x, the carboxylic OH group of pefloxacin shifted to 11.40ppm while the OH group of ascorbic acid shifted to 13.03 and 13.16ppm respectively. These shifts suggests the participation of atoms number carboxylic OH and OH of ascorbic acid in coordination. The ¹H NMR spectrum of [Fe(PfAs)]_x showed that the carboxylic OH of pefloxacin shifted to 11.38ppm. The chemical shift value 12.73 and 12.75ppm were assigned to atoms number 7 and 8 which are the OH groups from ascorbic acid. The chemical shift values were shifted downfield compared to the free ascorbic acid. These shifts suggest the involvement of the OH group in coordination.

The ¹³C NMR spectrum of pefloxacin and ascorbic acid ligands were compared with their complexes. The chemical shift value for the C=O carboxylic acid of pefloxacin appeared at 165.62ppm while the C=O of ketone appeared at 175.82ppm. The carbonyl group in the ascorbic acid was assigned chemical shift value of 173.96ppm. In the ¹³C NMR spectrum of [Co(PfAs)]_x, the C=O carboxylic acid of pefloxacin shifted to 188.27ppm and the C=O of ketone group shifted to 185.20ppm while the carbonyl group in ascorbic acid shifted to 183.23ppm. These shifts suggest the involvement of carbonyl of acid, ketone and ascorbic acid ketone in complexation. The ¹³C NMR spectrum of [Fe(OfAs)]_x, showed that C=O carboxylic acid shifted to 192.20ppm and the C=O ketone group shifted to 187.22ppm in the complex while C=O in the ascorbic acid shifted to 184.21ppm in the complex. These shifts suggest the involvement of carbonyl of acid, ketone and ascorbic acid ketone in coordination. The proposed structure of the mixed ligand complexes are shown in Figure 1 and 2 respectively.

Figure 1: Proposed structure of [Fe(PfAs)]_x

Figure 2: Proposed structure of [Co(PfAs)]_x

Antibacterial studies:

The antibacterial activities of the ligands and their complexes were tested against five bacteria species; which include S. aureus, E. coli., Bacillus subtilis, Pseudominas Spp. and Candida Spp. The antibacterial activity of the compounds was estimated on the basis of the average size of inhibition zone formed around the well on the seeded agar plate. The zone of inhibition (mm) of the Fe complex was significantly higher (P < 0.05) than the Co complex and pefloxacin against Staphylococcus aureus. The Co(II) mixed ligand complex was significantly higher (P < 0.05) than the pefloxacin and Fe(II) mixed ligand complex against E. coli., Pseudominas Spp. and Candida Spp. There was no significant difference (P > 0.05) for pefloxacin and Fe complex, while the Co complex decreases significantly (P < 0.05) against Bacillus subtilis. It was observed that metal chelation has affected significantly the antibacterial behaviour of the ligands. The complexes are observed to have a higher zone of inhibition on all the organisms as against the ligand (pefloxacin) except for E. coli which have the pefloxacin ligand to have high zone of inhibition than the Fe(II) complex but the Co(II) complex has the highest zone of inhibition of them all. A comparative study of the ligands and their complexes indicates that complexes exhibit higher antibacterial activity than the free ligands²⁶ .

The study on the minimum inhibitory concentration (MIC) of both the ligand (peloxacin) and their mixed ligand complexes are presented in Table 9. In the free ligand, the result showed that there were growth of the microbes (S. aureus, E. coli., Bacillus subtilis, Pseudominas Spp. and Candida Spp) inoculated at 0.025 μg/ml, growth was observe by Candida Spp at 0.05 μg/ml. The Fe(II) mixed ligand complex showed growth of the microbes at 0.025 μg/ml. Growth of Candida spp was observed at 0.05 μg/ml. For Co(II) mixed ligand complex, growth of the microbes was observed at 0.025 μg/ml. Growth of S. aureus, Bacillus subtilis and Candida Spp. was observed at 0.05 μg/ml. There was no growth of microbes at 0/1 μg/ml in the ligand and complexes.

CONCLUSION:

The search for novel drugs to treat diseases has continued to attract the interest of inorganic coordination chemists. Fe (II) and Co (II) complexes of mixed pefloxacin and ascorbic acid have been synthesized and characterized using physical and spectroscopic methods. The mixed ligand complexes possessed better physical properties than their parent ligands. The spectroscopic analysis suggests that the ligands are coordinating and shows octahedral geometry. The high melting point of the mixed ligand complexes confirmed the formation of the complexes, the colour of the mixed complexes is due to d - d electron transitions or charge transfer from the ligand to the metal ion. The antibacterial activity of the ligand and the mixed ligand complexes was carried out against S. aureus, E. coli., Bacillus subtilis, Pseudominas Spp. and Candida Spp. The mixed ligand complexes of pefloxacin-ascorbic acid shows higher antibacterial activity compared with the free ligand. It was observed that antibacterial behavior of the mixed ligand complexes were significantly higher (P < 0.05) than the free ligands against tested species.

CONFLICT OF INTEREST:

The authors declare no conflict of interest.

REFERENCES:

1. Fahmideh S, Lotf AS, Shahriar G. Synthesis, characterization and anti-tumour activity of Fe(III) Schiff base complexes with unsymmetric tetradentate ligands. Bull. Chem. Soc. Ethiop., 2010; 24: 193-199.

2. Ajibade P. Metal complexes in the management of parasitic diseases: In vitro antiprotozoal studies of metal complexes of some antimalarial drugs. Curr. Sci., 2008; 95: 1673 - 1679.

3. Ogunniran KO, Ajanaku KO, James OO, Ajani OO, Adekoya JA and Nwinyi OC. Synthesis, Characterization, antimicrobial activity and toxicology study of some metal complexes of mixed antibiotics. Afri, J. Pure and Appli., Chem., 2008; 2(7): 69 – 74.

4. Osunlaja AA, Ndahi NP and Ameh JA. Synthesis, physic-chemical and antimicrobial properties of Co(II), Ni(II) and Cu(II) mixed ligand complexes of demethylglyoxime. African J. Biotech., 2009; 8(1): 4-11.

5. Sunil SP, Ganesh AT and Vishwanath RP. Synthesis, spectral and biological studies on some mixed ligand Ni(II) complexes. Acta Poloniae Pharmaceutica – Drug Research, 2009; 66: 271-277.

6. Mohammed FK, Mohammed A and Gul MK. Synthesis and evaluation of biological and pharmacological activities of a novel acetylderivaties and copper complexes of Tranexamic acid. J. Biol, Sci., 2002; 2(3): 145 – 150.

7. Navarro M, Cisneros-Fajardo EJ, Lehmann T, Sanchez-Delgado RA, Atencho R, Silva P, Lira R and Urbina JA. Toward a Novel-Based chemotherapy against Tropical Diseases: Synthesis and characterization of New Copper(II) and Gold(I) Clotrimazole and Ketoconazole complexes and evaluation of their activity against Trypanosoma cruzi, Inorg. Chem., 2001; 40: 6879 – 6884.

8. Mostafa SI, Hadjiliadis N. New biologically active transition metal complexes of 2-mercapto-4,6-diamino-5-hydroxypyrimidine. Inorganic Chemistry: An Indian Journal. 2007; 2(3): 186–192.

9. Mostafa SI, Hadjiliadis N. New biologically active transition metal complexes of 2-mercapto-4,6-diamino-5-hydroxypyrimidine. Inorganic Chemistry: An Indian Journal. 2007; 2(3): 186–192.

10. Ogunniran KO, Ajani OO, Ehi-Eromosele CO, Obaleye JA,  Adekoya JA. and Ajanaku CO. Cu(II) and Fe(III) complexes of sulphadoxine mixed with pyramethamine: Synthesis, characterization, antimicrobial and toxicology study. International Journal of Physical Sciences 2012; 7(13): 1998 – 2005.

11. Lawal A and Obaleye JA. Synthesis, spectroscopic characterization and antibacterial study of mixed Thiamine-Nicotinamide metal complexes. Nig. J. Pure and Appl., Sci., 2013; 26: 2438 – 2445.

12. Lawal A, Amolegbe SA, Rajee AO, Babamale HF and Yunus-Issa MT. Synthesis, characterization and antimicrobial activity of mixed ascorbic acid - nicotinamide metal complexes. Bayero Journal of Pure and Applied Sciences, 2015; 8(1): 139 – 142.

13. Obaleye JA, Akinreme CA, Balogun EA and Adebayo JO. Toxicological studies and antimicrobial properties of some Iron (III) complexes of Ciprofloxacin. Afr. J. Biotech., 2007; 6: 2826 – 2832.

14. Abd EW and El S. Derivatives of phosphate Schiff based transition metal complexes: synthesis, studies and biological activity. Spect. Acta, 2004; 60: (1-2): 271 – 277.

15. Cheesebrough M. District Laboratory Practice in Tropical Countries. Part 2. Cambridge University Press. 2004; pp. 223 - 229.

16. Onyenze U. and Otuokere IE. Co(II) and Fe(II) mixed ligand complexes of Ofloxacin and Ascorbic acid: Synthesis, Characterization and Antibacterial Studies. Journal of Chemistry and Chemical research, 2016; 1(1): 39 - 42.

17. Zeinab HA. Mononuclear metal complexes of organic carboxylic acid derivatives: Synthesis, spectroscopic characterization, thermal investigation and antimicrobial activity. Elsevier B.V., 2006; 10(38): 1016-1022

18. Bamigboye MO, Obaleye JA. and Isaac YA. Synthesis and characterization of mixed sulphadiazine- ampicillin complexes. CSN proceedings, 2011; ING/007 ING035-ING041

19. William HD and Fleming J . Spectroscopic methods in Organic chemistry; Tata McGraw-Hill Shomareh Rahnama: 1980; pp. 3516

20. McCleverty JA and Meyer TJ. Comprehensive Coordination Chemistry II: From Biology to Nanotechnology. 2nd Edn., Elsevier, Amsterdam. Netherlands, 2003; pp. 232-236.

21. Halli M, Shashidhar B and Quresi ZS. Synthesis, Spectral Studies, and Biological Activity of Metal Complexes of Benzofuran Thiosemicarbazides. Synthesis and reactivity in inorganic and metal-organic chemistry, 2004; 34(10): 1755-1768

22. Anacona JR, Johan C and Ovidio AA. Synthesis, Spectroscopic, and Magnetic Studies of Mono- and Polynuclear Schiff Base Metal Complexes Containing Salicylidene-Cefotaxime Ligand. International Journal of Inorganic Chemistry. 2013; 1-7

23. Madalina VA, Stefania FB, Constantin D, Gabriela LA. Synthesis, Characterization and Structural Studies of Binuclear Nickel(II) Complexes derived from dihydroxybenzaldehyde thiosemicarbazones, bridged by 1,2 bis(diphenylphosphino)ethane.  Eur. J. Med. Chem., 2010; 45: 2055 – 2062

24. Vidyavati R, Nirdosh P. and Angadi SD. Synthesis, Characterization and Antimicrobial Activity of Cu(II), Co(II) and Ni(II) Complexes with O, N, and S Donor Ligands. E-Journal of Chemistry, 2008; 5 (3): 577-583.

25. Atkins PW, Overton TI, Rourke JP, Weller MT and Armstrong FA. Shriver and Atkins’ Inorganic Chemistry: Fifth Edition. Oxford University press. 2010; 497.

26. Chohan ZH, Supuran CT and Scozzafava A. Metal-Based Antibacterial and Antifungal Agents: Synthesis, Characterization, and In Vitro Biological Evaluation of Co(II), Cu(II), Ni(II), and Zn(II) complexes with Amino Acid-Derived Compounds.  J. Enzyme Inhib. Med. Chem., 2004;. 20: 1979-1985.

Received on 03.10.2016       Modified on 24.10.2016

Accepted on 30.10.2016      ©A&V Publications All right reserved

Research J. Science and Tech. 2016; 8(4):215-220.

DOI: 10.5958/2349-2988.2016.00032.2