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European Journal of Applied Sciences – Vol. 10, No. 1
Publication Date: February 25, 2022
DOI:10.14738/aivp.101.11704. Olagboye, S. A. (2022). Synthesis, Characterization and Antimicrobial Activities of mixed Ligand Metals Complexes with
Trimethoprim and Potassium Thiocyanate. European Journal of Applied Sciences, 10(1). 428-439.
Services for Science and Education – United Kingdom
Synthesis, Characterization and Antimicrobial Activities of mixed
Ligand Metals Complexes with Trimethoprim and Potassium
Thiocyanate
Olagboye S. A.
Department of Chemistry, Faculty of Science
Ekiti State University, Ado-Ekiti, Nigeria
ABSTRACT
A new series of Mn (II) and Ni (II) mixed ligands-metal complexes derived from
trimethoprim (TMP) and thiocyanate (TC) have been synthesized in aqueous
medium and characterized by spectroscopic studies using IR. The coordination of
the two ligands towards central metal ions has been proposed in the light of
elemental analysis using barium chloride gravimetric method, various colours of
metal complexes were obtained ranging from green to light green and found to be
soluble in ethanol, butanol, and insoluble in n-hexane, propan-2-ol, and benzene.
The following physical parameters were also observed; solubility, melting point
and conductivity. The results of the physical and spectroscopic data confirmed that
the ligands are chelating agents. The results of spectroscopic studies revealed that
TMP acts as a mono-dentate ligand coordinating through the nitrogen of the
pyrimidine group and coordination through the nitrogen of the amine group, while
in the TC coordination occurred through the sulphur and nitrogen groups because
thiocyanate shares its negative charge approximately equally between sulfur and
nitrogen. As a consequence, thiocyanate can act as a nucleophile at either sulfur or
nitrogen, it is an ambidentate ligand. Antimicrobial activity of the mixed ligands
metal complexes and the free ligands were carried out against the bacterial
Escherichia coli, Staphylococcus aureus, Klebsiella pneumonia, Pseudomonas
aeruginosa, Bacillius subtilis and the fungi; Sclerotinia trifoliorium, Fusarium
oxyporium, Stemania paradoxa, Brotrytis cinerea. The mixed ligands metal
complexes showed higher activities when compared to the free ligands of TMP but
were less active than the free TC ligand. The complexes of Mn (II) showed the
highest antimicrobial activity while the Ni (II) complex showed the least activity
against the bacterial and fungi organisms. Structure activity relationship showed
that Ni (II) complexes containing sulphate ions are more active, while for Mn (II)
complexes containing thiocyanate ions showed more enhanced activity than those
containing sulphate ions.
Keyword: Trimethoprim; Thiocyanate; Staphylococcus aureus; Stemania paradoxa
INTRODUCTION
Trimethoprim is an antibiotic used to treat bacterial infections such as prophyaxis and
treatment for urinary tract infections [1, 2]. It works by stopping the growth of bacteria. This
antibiotic treats only bacterial infections. It will not work for viral infections (such as common
cold, flu). Using any antibiotic when it is not needed can cause it to not work for future
infections. Thiocyanate blocks active ingestion of inorganic iodide by the thyroid. It prevents
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Olagboye, S. A. (2022). Synthesis, Characterization and Antimicrobial Activities of mixed Ligand Metals Complexes with Trimethoprim and Potassium
Thiocyanate. European Journal of Applied Sciences, 10(1). 428-439.
URL: http://dx.doi.org/10.14738/aivp.101.11704
the enzyme thyroperoxidase, thereby inhibiting the incorporation of iodine into thyroglobulin
thereby contributing to the hyperthyroid effect of vegetables. Thiocyanate is a competitive
inhibitor of the sodium iodide symporter (NIS) at thiocyanate levels normally found in blood.
Thereby, it worsens iodine deficiency by inhibition of thyroidal iodide accumulation and by
inhibition of iodide transport into breast milk for infant nutrition. Thiocyanates are a group of
compounds formed from a combination of sulfur, carbon, and nitrogen. Thiocyanates are found
in various foods and plants.
They are produced primarily from the reaction of free cyanide with sulfur. It is also a break
down product of Gls. Although thiocyanates are less harmful than cyanide in humans, they are
known to affect the thyroid glands, reducing the ability of the gland to produce hormones that
are necessary for the normal function of the body [3]. Dietary or nutritional thiocyanate is a
very important substance necessary for optimal health and well-being. Thiocyanate is found in
specific foods, common to the indigenous African diet as well as some Middle Eastern and
Mediterranean diets. When thiocyanate is present in the diet, it acts as an oxygen carrier and
increases the capacity of the blood to transport the life-giving oxygen to every single cell of the
body. Because of its oxygen – enhancing properties, a diet rich in thiocyanate is effective in
helping mitigate sickling of the red blood cells [4]. Exposure to thiocyanate corresponds to a
decrease in iodine intake. Cessation of smoking, reduction of industrial pollution and improved
diet will reduce the role of thiocyanate in thyroid disease. Large amounts of thiocyanate are
generated in people with a high intake of cyanide from tobacco smoking, from cyanide in food,
or from industrial pollution of the environment with cyanide. In individuals exposed to high
levels of thiocyanate, adverse effects may be prevented by an increase in iodine intake. In areas
of low iodine intake, thiocyanate exposure increases the risk of developmental and other iodine
deficiency disorders. As the overall effect of thiocyanate is to hamper utilization of iodide, the
main effect of thiocyanate is to worsen iodine deficiency. By this mechanism thiocyanate is one
of the most important environmental compounds influencing the occurrence of thyroid disease.
Thiocyanate shares its negative charge approximately equally between sulfur and nitrogen. As
a consequence, thiocyanate can act as a nucleophile at either sulfur or nitrogen, it is
an ambidentate ligand. [SCN]− can also bridge two (M−SCN−M) or even three metals (>SCN− or
−SCN<). Experimental evidence leads to the general conclusion that class A metals (hard acids)
tend to form N-bonded thiocyanate complexes, whereas class B metals (soft acids) tend to
form S-bonded thiocyanate complexes. Other factors, e.g. kinetics and solubility, are sometimes
involved, and linkage isomerism can occur, for example [Co(NH3)5(NCS)]Cl2 and
[Co(NH3)5(SCN)]Cl2.
The realization of metal chelates increases the lipophilicity of the bioactive compounds and
effective permeability of the compounds into the site of action [5]. Antibiotics have modernized
medicine but the rapid appearance of resistant strains remains a challenge [6]. This has
prompted the search for novel drugs for bacterial chemotherapy. Metal-ligand (drug)
complexation is one of the chemotherapeutic routes to inducing biological activity of medicinal
agents. The biochemical activity of bioactive species can be boosted by chelation also,
chelation reduces the polarity of the metal ion due to overlapping of the ligand orbital and
partial sharing of the positive charge of the metal ion [7]. Additionally, such complexes intensify
the respiration of the cell and as a result, the growth of the organism is limited by upsetting the
protein synthesis.
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Transition metal complexes are cationic, neutral or anionic species in which a transition metal
is coordinated by ligands [8, 9]. Transition metal ions are known to play very important roles
in biological processes in the human body. For example, Zn (II) and Cu (II) ions are the second
and third most abundant transition metals in humans [10, 11]. They are found either at the
active sites or as structural components of a good number of enzymes. Cobalt is present in
vitamin B12, a co-enzyme that plays significant roles in some biochemical processes. There are
numerous lists of transition metals which are effective therapeutic agents especially when
coordinated to a ligand to form metal complexes [12]. A list of metal containing compounds
used in chemotherapy for treatment of diseases include platinum (anticancer),
silver(antimicrobial), gold (antiarthritic), bismuth (antiulcer), antimony (antiprotozoal),
vanadium (antidiabetic) and iron (antimalaria) [13]. Nitrogen containing chiral ligands have
found wide applications in chemotherapy and asymmetric catalysis. Among them 1, 10 –
phenanthroline is particularly attractive for its ability to coordinate several metal ions, and thus
to generate different catalytic species involved in a great variety of reactions [14]. The ligand
(1, 10 – phenanthroline) is a strong field bidentate ligand that forms very stable chelates with
many first row transition metals [15]. Salicylic acid is biosynthesized from the amino acid
phenylalanine and can be produced by sodium salicylate Diarmiud, [16] and Philip, [17]. In
modern medicine, salicylic acid and its derivatives are used as constituents of some rubefacient
products, for example, methyl salicylate is used as a liniment to soothe joint and muscle pain,
choline salicylate is used typically to relieve the pain of aphthous ulcers [18]. This study was
undertaken to give an account on the synthesis, characterization and antimicrobial activity
studies of mixed ligands metal complexes of trimethoprim and thiocynate.
MATERIALS AND METHODS
Reagents and Instruments
All the chemicals were obtained commercially and used as received. Pure sample of
Trimethoprim salt, molecular formula C14H18N4O3, and potassium thiocyanate (KSCN) salt were
obtained from Sigma – Aldrick. Metal salts MnSO4.6H2O and NiSO4.6H2O were obtained British
Drug Chemical House Limited Co, Poole, England. Analytical Reagent grade hydrated metal
sulphides from Bristish Scientific Chemicals were used for the preparation of the complexes.
Elemental analysis (C, H, N and O) were carried out using micro analytical technique on C, H, N,
S, O Elemental analyzer at Universiti Technologi Petronas (UTP) Malaysia. Other reagents
includes ethanol C2H5OH, chloroform (CCl4), propan-2-ol (CH3CHOHCH3), benzene, butanol, n- hexane, toluene, acetone, hydrochloric acid, hydrogen peroxide, and nitric acid. The melting
points were carried out on a Gallenkamp melting point apparatus. Infra-red spectral analyses
were recorded using Shimadzu FTIR-8400S (Fourier Transform Infrared Spectrophotometer)
in the range 4500 – 300 cm-1. The solid reflectance studies were also determined using a double
beam machine scan in the range 200 – 800 nm.
Synthesis
The complexes were synthesized by the procedure described by Idemudia et al. [19] with minor
variation. A methanolic solution of the metal salt and the ligands were mixed in a mole ratio of
1:1; 1:2; 1:1:1; 1:2:1 and refluxed at a constant temperature of 1000C for 3 hours 30 minutes.
The complexes were recovered after two days, washed and dried in a desiccator. Digestion was
carried out by weighing 0.05g of the complex into a beaker, then add about 10ml of 2% NaOH
solution to it. Heat until all the H2O2 escaped. Allow to cool down and transferring the content
into a 50ml standard flask and add distilled water to the mark.
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Olagboye, S. A. (2022). Synthesis, Characterization and Antimicrobial Activities of mixed Ligand Metals Complexes with Trimethoprim and Potassium
Thiocyanate. European Journal of Applied Sciences, 10(1). 428-439.
URL: http://dx.doi.org/10.14738/aivp.101.11704
After digestion the sample was acidified with HCl to obtained pH of 1 and heated to 950C -
1000C. 10ml of 5% BaCl2, barium chloride solution was added and stirred continuously for 2-
3minutes and leaves the emerging precipitate overnight. The precipitate was filtered using
sintered glass and the precipitate was washed with boiling water. The residue was kept inside
desiccator and sulphur in form of sulphate was calculated as stated below:
% of sulphur determination in the complexes
Percentage sulphur = �������� �������
������ �� ������
� ���
1g of BaSO4 = ��
������ �� ������
� ���
% of sulphur = 789:; <8;.>?@AB9 × D?@AB9 8E F:GHI × J.KLML
N8;.8E :;@OP89 × D?@AB9 8E Q:RS;?
� 100
Weight of BaSO4 = Difference of final and initial weight
Antibacterial Activities
The test microorganisms used for screening antimicrobial activities were standard pathogenic
stains obtained from the culture collection unit of the Department of Microbiology, Ondo state
University Teaching Hospital, Akure, Nigeria. The laboratory tests were carried out at the Pest
and Control Section of the Department of Crops and protection, Federal University of
Technology, Akure, Nigeria. The antimicrobial activities of newly generated complexes were
screened against the following fungi: Sclerotium roofil, Mansourian phomoides, Collectotrichum
lindimuchianum. Using poisoned food techniques at 0.025g/ml concentration, under sterile
culture molten potato dextrose (PDA) and solvent used was dimethylsulphuroxide at
0.025g/ml concentration. A negative control plate (NTR) without any treatment was also set
up. The mycelia growth inhibition was calculated in percentage [20]. All newly synthesized
complexes were tested for their antibacterial activities against Streptococcus fecalis,
Xantomonas axinopolis, Salmonella entrica, Clavibacter michiganense, Xanthomonas phaseoli
alongside with the control (amoxillin), and using Broth Dilution method. At 0.035g/ml
concentrations. The MIC (minimal inhibitory concentration) of the control organism is used and
read to check the accuracy of the complexes [21]. The lowest concentration inhibiting growth
of the organism is recorded as the MIC. This result is compared with the control amoxillin.
Mycelia growth were measured with the aid of Vernier calipers, mycelia growth inhibition were
calculated in percentage using the formula:
% ZONE OF INHIBITION = TUV W UV
UV
� 100
Where NTR= Average diameter of fungal colony in negative control sets (plates without any
treatment) and TR= Average diameter of fungal colony in treated sets.
RESULTS AND DISCUSSION
Results
The physical properties of nickel and manganese (II) were shown in Tables (1a and b). Tables
(2a and b) shows the ratio of different solvent used for the solubility tests of nickel and
manganese complexes. Tables (3a and b) shown the elemental analysis of sulfur using
gravimetric method and Table (4a and b) redeemed the prominent regions of FTIR spectra of
mixed ligand complexes with nickel and manganese (II) while the evaluation of antifungal
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
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activities of Ni2+ and Mn2+ complexes are shown in Tables 5 and 6 respectively. And finally,
evaluation of antibacterial screening of Ni2+ and Mn2+complexes are shown in Table 7 and 8.
Table1a: physical properties of Nickel (II) complex
COMPLEX RATIO COLOUR %YIELD MELTING POINT
NiLSO4(H2O2)2 1:1 Light green 40% 140-2500C
NiL2SO4(H2O2)2 1:2 Light green 40% 90-1800C
NiLSCNSO4(H2O2)2 1:1:1 Green 40% 100-2100C
NiL2SCNSO4(H2O2)2 1:2:1 Green 40% 70-1950C
Table1b: physical properties of manganese complex
COMPLEX RATIO COLOUR %YIELD MELTING POINT
MnLSO4(H2O2)2 1:1 Light brown 40% 140-2500C
MnL2SO4(H2O2)2 1:2 Light brown 40% 100-2000C
MnLSCNSO4(H2O2)2 1:1:1 Brown 40% 90-1900C
MnL2SCNSO4(H2O2)2 1:2:1 Brown 40% 50-1400C
Table2a: Solubility of the Nickel (II) complex
Complex Ratio Toluene Benzene Ethanol Hexane Acetone
NiLSO4(H2O2)2 1:1 Insoluble Soluble Solution Insoluble Slightly
soluble
NiL2SO4(H2O2)2 1:2 Insoluble Soluble Soluble Insoluble Slightly
soluble
NiLSCNSO4(H2O2)2 1:1:1 Insoluble Soluble Soluble Insoluble Slightly
soluble
NiL2SCNSO4(H2O2)2 1:2:1 Insoluble Soluble Soluble Insoluble Slightly
soluble
C14H18N4O3
Table2b: Solubility of the manganese (II) complex
Complex Ratio Acetone Butanol Ethanol Carbontetrachloride Benzene
MnLSO4(H2O2)2 1:1 Soluble Insoluble Soluble Soluble Soluble
MnL2SO4(H2O2)2 1:2 Soluble Insoluble Soluble Soluble Soluble
MnLSCNSO4(H2O2)2 1:1:1 Soluble Insoluble Soluble Soluble Soluble
MnL2SCNSO4(H2O2)2 1:2:1 Soluble Insoluble Soluble Soluble Soluble
C14H18N4O3
Table 3a: Elemental analysis of sulphur using gravimetric
Complex Ratio Initial Final Amt. of S found
Amt. of S
in the
complex
NiLSO4(H2O2)2 1:1 29.26 29.3 0.4g 10.9
NiL2SO4(H2O2)2 1:2 29.53 29.59 0.6g 16.4
NiLSCNSO4(H2O2)2 1:1:1 29.26 29.34 0.8g 21.9
NiL2SCNSO4(H2O2)2 1:2:1 29.26 2933 0.5g 13.7
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Olagboye, S. A. (2022). Synthesis, Characterization and Antimicrobial Activities of mixed Ligand Metals Complexes with Trimethoprim and Potassium
Thiocyanate. European Journal of Applied Sciences, 10(1). 428-439.
URL: http://dx.doi.org/10.14738/aivp.101.11704
Table 3b: Elemental analysis of sulphur using gravimetric
Complex Ratio Initial Final Amt. of S found
Amt. of S
in the
complex
MnLSO4(H2O2)2 1:1 29.26 29.31 0.5g 13.7
MnL2SO4(H2O2)2 1:2 29.26 29.62 0.9g 24.6
MnLSCNSO4(H2O2)2 1:1:1 29.53 29.6 0.7g 19.2
MnL2SCNSO4(H2O2)2 1:2:1 29.26 29.32 0.6g 16.4
Where S= Sulphur
Table 4a: PROMINENT IR SPECTRA BANDS (cm-1) OF NICKEL
Ligand MnLSO4(H2O2)2 MnL2SO4(H2O2)2 MnLSO4(H2O2)2
400-
600 504.4 406.99,509.22 389.31,509.22
600-
800 609.53,786.98(H2O) 786.98(H2O) 789.98(H2O)
800-
1000 830,860,903,993 994.34(SO4)2- 1123.57(SO4)2- 1125.5(SO4)2-
1000
-
1200
1,005,103,911,351,15
0 1125.5(SO4)2- 1123.54(SO4)2- 1125.5(SO4)2-
1200
-
1400
1290,1337 (CN) 1238.34(CN)1336.71 1238.34(CN)1337.6
8
1238.34(C- N)1335.75
1400
-
1600
14,501,455 1451.48 1452.5 1457.27
1600
-
1800
1650(C=O) 1627.97(C=O) 1624.12(C=O) 1629.9(C=O)
1800
-
2000
1854.62,1979.03(C=
H) 1981.92(C=N) 1978.07, (C=N)
2000
-
2200
SCN 2195.07-S-(C=N)
2200
-
2400
2400
-
2600
2571
2600
-
2800
2798 2720.7 2712
2800
-
3000
2879-(C-H) 2930.93(C-H) 2937.68(C-H) 2932.86(C-H)
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3000
-
3200
3140.22(-C=H) 3138.3 3136.36
3200
-
3400
3320-(NH2) 3310.92-(NH2) 3310.92(NH2) 3311.89(NH2)
3400
-
3600
34789(NH) 3465.23(NH) 3466.2(N-H) 3468.1(N-H)
3600
-
3800
3768.07
3800
-
4000
3886.69,3979.28 3879.94(OH) 3895.37(OH),3909.8
4
4000
-
4200
4200
-
4400
4230.03,4391.1
4400
-
4600
4457.64(-OH) 4466.32,4481.75
Table 4b: PROMINENT IR SPECTRA BANDS (cm-1) OF MANGANESE
Ligand NiLSO4(H2O2)2 NiL2SO4(H2O2)2 NiL2SO4(H2O2)2
400-
600 406.99,481.26 398.31,509.22 404.1,471.61
600-
800 606.63(H2O) 786.98(H2O) 606.63(H2O)
800-
1000 830,860,903,993 (Ni-L) 991.44(Ni-L) (Ni-L)
1000-
1200 1,005,103,911,351,150 1010.73,1124.5
(SO4)2- 1125.50(SO4)2- 1011.7(SO4)2-
1125.5
1200-
1400 1290,1337 (CN) 1242.2 1238.34(CN)1335.75 1238.34(C- N)1335.75
1400-
1600 14,501,455 1460.16 1457.27 1458.23
1600-
1800 1650 1624.12(C=O) 1629.27(C=O) 1626.05, (C=O)
1800-
2000 1978.07(C=N) 1851.72, (C=N)
2000-
2200 2020.5 2195.07 2019.54, (C=N)
2200-
2400 2279.94,-S-(C=N)
2400-
2600 2571 2407.24
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Olagboye, S. A. (2022). Synthesis, Characterization and Antimicrobial Activities of mixed Ligand Metals Complexes with Trimethoprim and Potassium
Thiocyanate. European Journal of Applied Sciences, 10(1). 428-439.
URL: http://dx.doi.org/10.14738/aivp.101.11704
2600-
2800 2798 2712.97
2800-
3000 2879-(C-H) 2838.35,2932.86 2927.08(C-H)
3000-
3200 3136.36(N-H) 3144.08(N-H)
3200-
3400 3320(NH2) 3311.86(NH) 3324.42(-NH)
3400-
3600 3478(-NH) 3468.13,3560.71 3468.1(-COOH)
3600-
3800 3600.25,3747.81
3800-
4000 3879.94(OH) 3865.45
4000-
4200 FREE (OH)
4200-
4400
4400-
4600 4466.32 4473.07
4600-
4800 FREE (OH) FREE (OH)
Table 5: Antibacterial Activity of Mn (Ii) Complex
Complex X.unto B.sub B.curve E.coli P.aur P.sign E.coli S.aures
MnLSO4(H2O2)2 16 20 - - - - - 6
MnL2SO4(H2O2)2 15 5 23 6 - - - 14
MnLSCNSO4(H2O2)2 - - - - 32 6 21 -
CIPRO 24 40 41 27 31 34 35 40
STRED 24 42 36 36 20 22 26 33
METRO 22 27 21 22 23 26 33 32
Table 6: Antibacterial Activity of Ni (Ii) Complex
Complex X.unto B.sub B.curve E.coli P.aur P.sign E.coli S.aures
NiLSO4(H2O2)2 - - 20 32 32 18 27 31
NiL2SO4(H2O2)2 - - 24 15 28 18 26 25
NiLSCNSO4(H2O2)2 - - 10 - 36 6 24 21
NiL2SCNSO4(H2O2)2 - - 24 15 28 18 26 25
CIPRO 24 40 41 27 31 34 35 40
STRED 24 42 36 36 20 22 26 33
METRO 22 27 21 22 23 26 33 32
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Table 7: The Antifungi Result of Ni (Ii) Complex
Complex Selerotium
rolfsii
Collectotricium
capsicia
Collectotricium
capsicia
NiLSO4(H2O2)2 81(27.68)% 60(36.17)% 41(10.86)%
NiL2SO4(H2O2)2 82(26.79)% 22.5(76.06)% (No inhibition)
NiLSCNSO4(H2O2)2 16.5(85.36)% 28(67.82)% 13(52.42)%
NTR 112 NTR=94 NTR=46
Table 8: The Antifungi Result of Mn (Ii) Complex
Complex Selerotium
rolfsii
Collectotricium
lindi
Collectotricium
capsicia
NiLSO4(H2O2)2 87.5(21.88)% 56(40.43)% (No inhibition)
NiL2SO4(H2O2)2 31(72.32)% 17(81.92)% 18(60.87)%
NiLSCNSO4(H2O2)2 90(19.64)% 68(27.66)% 33(4.35)%
NTR 112 NTR=94 NTR=46
DISCUSSION
All the complexes formed were colored, pale green being the most predominant color, showing
that ligand dominates the metal ions. The percentage yields of the complexes were below 100%
increased as the concentration increased, the melting point of complexes Ni and Mn (II) ions
ranges from 50-2500C according to results in Table 1a and b. Table 2a and b showed the
solubility of the metal Ni and Mn (II) ions complexes, and the results indicated that they were
most soluble in ethanol and benzene, Mn ion complexes also soluble in acetone. The gravimetric
analysis advocated for the presence of sulfur in the metal-ligand complexes and the amount of
sulfur present in each sample, following analytical procedure was higher in Mn than Ni ion,
Table 3a, and b.
The infra-red spectroscopic studies of nickel and manganese (II) ion complexes demonstrated
different bands between the ligands and metal complexes as shown in Table 4a and b, the bands
found around 4500-500cm-1. The prominent bands in the free ligand were 432.15, 521.51 with
some pronounced bands at 620.52, 607.42, and 625.89 cm-1 this validates the coordination of
metal to the ligand through the nitrogen atom [7]. The absorption bands at 3748-3760 in cm-1
found in the metal complexes revealed the presence of the –OH group from the water of
crystallization of Ni (II) salt.
The strong peak at 1625 cm-1 in the mixed ligand complexes of the nickel showed the presence
of the C=N group in the other complex and the free ligand [22]. The prominent bands at 1554
cm-1 and 1677 cm-1 in the free ligand complexes whose shifted from 1382 to 1765 cm-1 in the
metal complexes, have shown the presence of C=O bonds. Also, the characteristics peak of -S- C=N found around 2195 cm-1 was as a result of thiocyanate present in the mixed ligand of
trimethoprim and metals ion [23]. All the complexes formed in the region of 3550-3450 cm-1
have weak and broad bands responsible for the vibrational peaks at this region O-H stretch
vibration (intermolecular hydrogen bonding). Olagboye [24] stated that the -OH band could be
attached to the activities of water present in the complexes and synthesis. All the complexes of
Trimethoprim and the mixed ligand (thiocyanate) showed bands at 406, 404 cm-1 and 504, 509
cm-1 at lower frequency regions indicating the coordination of metal ions to the ligand, and this
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Olagboye, S. A. (2022). Synthesis, Characterization and Antimicrobial Activities of mixed Ligand Metals Complexes with Trimethoprim and Potassium
Thiocyanate. European Journal of Applied Sciences, 10(1). 428-439.
URL: http://dx.doi.org/10.14738/aivp.101.11704
fact had been demonstrated and supported by the results of elemental analysis (Mn-L). The
sharp band present at 1290 cm-1 in the ligand corresponding to VC=N disappeared in IR Spectra
of all the complexes while a new band at 1238, 1326, 1337, and 1335cm-1 seeing in the Mn (II)
complexes in attributed C=N [23]. The sharp peak found in the ligand 1650 cm-1 shows the
presence of C=O carbonyl in the ligand but with a pronounced shift in all-metal complexes to
1627, 1624, and 1629 cm-1 respectively, indicating coordination of metal ions (Mn) to the
ligand.
The infra-red spectroscopic studies of cobalt (II) ion complexes demonstrated different bands
between the ligands and metal complexes as shown in Table (4a and b), the bands found around
(3320) to 3478 cm-1 in the spectra of the ligand was assigned to V(NH) group. The coordination
of metal to the ligand through the nitrogen atom has shown in the complexes. The introduction
of thiocyanate ion into the complexes was evident regardless of a sharp peak appearing at
2279.94 cm-1 for the Mn mixed ligand complex as characterization peak for S-C=N ion from the
mixed ligand. The prominent peaks between 1011.7 to 1125 cm-1 found in the Ni (II) and Mn
(II) complexes were due to the participation of sulfate ions in the complexation confirmed by
the gravimetric analysis.
The bioactive activities were carried out against bacteria and fungi using metal-ligand
complexes; the results in this prospective showed no or little antimicrobial potency. All the
metal complexes are toxic and more or less to fungi species. According to Rahimzadeh et al.
[25], most complex metals inhibit the growth of organisms directly or indirectly. The results
obtained in Tables 5 to 8 give a correct account of the effectiveness of the drug-coated with Ni
assay against fungal disease than that of Mn supplements.
CONCLUSION
Having studied the synthesis, characterization, and antimicrobial activities of nickel (II) ion
complexes and manganese (II) ion complexes with Trimethoprim and thiocyanate mixed ligand
at different ratio concentrations. The solubility tests of the metal complexes in some organic
solvents confirmed that they are non-polar and non-electrolyte in nature. The IR spectroscopic
characterization revealed the position of attachment of the manganese (II) ion and nickel (II)
ion to the ligands manganese was through the oxygen atom of the carbonyl group (C=O) and
the nitrogen atom of N-H. The antimicrobial activities of manganese (II) ion and nickel (II) ion
revealed the bioactivity of the complexes, and they were better inhibitors of fungi and bacteria.
Coordination of metal-ligand reduces the polarity of the metal ion mainly because of the partial
sharing of its positive charge with donor groups within the chelate ring system. The increase in
the antibacterial activities of the complexes compared to the free ligands may be due to the
electropositive nature of metals, ultimately enhancing their antibacterial.
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 1, February-2022
Services for Science and Education – United Kingdom
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