Metal Complexes of Phenyl Glycine-O-Carboxylic Acid: Preparation, Characterization, Electrochemical and Biological Properties

Introduction

The study of coordination complexes reported the more than centuries till now it plays significant role in many fields especially in the pharmacy and pharmacology fields. It related to the combinations of organic and inorganic chemistry concerning the synthesis, characterization and their applications. It mostly concern their structure, complexes were considered those compounds which do not obey the classical theory of valence. The biological importance rich metal ions reported in divalent metals ions were cobalt, zinc, copper, manganese, and nickel owing the medicinal value all the five metals were selected for the this research. Naturally, the manganese obtained in daily life is only in trace amounts at different all forms. The human can 2 to 5 mg of vitamin B₁₂ and its derivatives, predominantly in the liver. Nickel gives the extraordinary binding potential for bone and skin which has played urged role in the skin pigmentations. Copper is extensively distributed in all human resources. Zinc is a very predominant micro-nutrient. A number of human diseases are compatriotic with lowered blood zinc.

The metal and carboxylate ligand coordination behaviors has been explored by several researches. The neutral ligand was decided for the present investigation. Newly formulated neutral ligand phenyl glycine -o- carboxylic acid is derived from anthranilic acid. A literature survey reported that the characterization of complexes of anthranilate ligands manifest different modes of coordination in which carboxylate anion and nitrogen of amine group^1-4and both the oxygen of carboxylic acid^5,6 The crystal structure of Lithium, Sodium, Thallium complexes of anthranoylanthranilic acid have meshed through the oxygen of carboxylate group with trihydrate water molecule was described⁷. An azomethine nitrogen and carboxylate oxygen of mannich base⁸ and Schiff base^9-11, obtained from anthranilic acid are documented. In this paper, we have given a detailed outline of the preparation, and interpretation of the synthesized metal complexes, furthermore, the electrochemical and biological behavior were studied. In addition to that, the antifungal and antibacterial efficacies of the ligand as well as synthesized five metal complexes were studied in comparative aspects.

Materials and Method

Materials

All the metal (II) chlorides like cobalt, nickel, manganese, zinc, and copper are hydrated forms which was used in the complexation process and are Merck and Sigma Aldrich grades. Ethanol, diethyl ether, anthranilic acid, chloroacetic acid, anhydrous sodium carbonate, and animal charcoal are acquired from Sigma Aldrich products.

Preparation of ligand

Figure 1: Synthesis of ligand. Click here to View figure

15 gms of anthranilic acid, 12 gm of chloroacetic acid, 22 gm of anhydrous sodium carbonate, and 200 ml of water are taken in one liter round bottom flask. Then reflux condenser is fitted and boil the mixture under reflux for about 3-4 hours. Then, cooled and acidified with the concentrated hydrochloric acid when a light brown precipitate of a ligand is obtained. After that, the mixture is allowed it to complexation overnight. Then it reaction mixture is filtered using the Buchner funnel and then wash with water. The collected solid compound is dissolved in hot water. To that the solution of a hot dilute acid is added followed by 1 gm decolorizing animal charcoal is mixed then boil and again filtered. Finally, the crystals of the pure product are obtained.

Preparation of the metal complexes

Appropriate amount of each metal chlorides and the ligand phenyl-glycine -o- carboxylic acid are dissolved by the ethanol solvent individually and then proper ratio of both are mixed well in the 500ml round bottom flask. After that, the whole contents in the RB flask highly refluxed with the aid of reflux condenser around six hours. Final mixture of solutions were again concentrated under water bath then, cooled followed by recrystallized the all five metal complexes. Thus, the complexes were prepared, and the excess ligand is separated by washing with ether and dried under vacuum and make into anhydrous with the help of calcium chloride environment.

Spectral Methods

The FT-IR of all five metal complexes were measured with pellets of KBr using Shimadzu 24 FT-IR 8400S spectrometer between the ranges of 4000-400 cm^-1. Then, the electronic spectra of five metal complexes and their ligands were read by using Hitachi U-3400 spectrophotometer in the range of 1100-320 nm using cuvettes. The ¹HNMR was measured by BRUKER 400MHz spectrometer using TMS as an internal standard, CDCl₃, and DMSO-D₆as the solvent. The magnetic susceptibility measurements of the complexes were calculated using Gouy’s balance at room temperature, and mercury tetrathiocynato cobaltate(II) was used as a calibrant. The molar conductance was recorded on Toshniwall’s conductivity meter in acetonitrile. All melting points in degrees Celsius were measured with a capillary device by using the Stuart melting point apparatus. The antimicrobial activity of ligand and the metal complexes cobalt, copper, and nickel have been examined inimical to three fungal and four bacteria by using the Agar diffusion method. The 100µL test solution in DMSO was added to the nutrient Agar plates and potato dextrose agar plates. The plates were incubated at 37°C for 24hours for bacteria and 28°C ± 2 °C for fungi. After 24 hours the diameter (mm) of the incubation zone was recorded.

Outcomes and Validation

Electrical conductance

The electrical conductance is weighed and the values of the molar conductance are tabulated in table 1. The conductance of cobalt(II)complex is 1:1 electrolytic in  nature¹². From the all the spectral analysis and conductance results, cobalt (II) chloride complex is assigned as [CoL₃]²⁺ [CoCl₄]².

Magnetic Susceptibility

The magnetic moment of the Manganese(II) chloride complex exhibits 5.93 B.M suggests that it exists in an octahedral geometry. The cobalt(II) chloride complex which is assigned to [CoL₃]²⁺ [CoCl₄]^2- with an octahedral geometry has a µ_eff of 4.46 B.M which is supported by conductance data and the remaining values of five metal complexes are given in table 1.

Melting Behaviour

On heating, the complexes decompose at a temperature above 200°C. It is revealed that all the complexes are stable. Melting behavior is tabulated in table 1.

Table 1: Physical parameters. 

Complex	Conductance Ohm-1 cm2 mol-1	Electrolytic nature	µeff B.M	Melting Point ℃	Colour
[Mn(L2)Cl2	57.21	1:0	5.93	252	Light Brown
[Co(L)3]2+[CoCl4]2-	140.89	1:1	4.46	245	Light Green
[Ni(L)2Cl2]	59.71	1:0	3.01	355	Light Yellow
[Cu(L)2Cl2]	59.71	1:0	1.7	210	Dark Brown
[Zn(L)2Cl2]	17.06	1:0	–	295	Yellow

L = Phenyl glycine o-carboxylic acid

Infra-Red Spectra of Complexes

The infra-Red spectrum of ligand has a band at 3373 cm^-1 is attributed to the OH group of carboxylic acids. The NH stretching vibrations is merged with the previous band. The band (1726 cm^-1) C=O of aliphatic acid. The band (1705 cm^-1) C=O of aromatic carboxylic acid. The band (1398 cm^-1) C-N stretching¹³. The strong band appears (1662 cm^-1) NH bending vibrations. The infra-red spectra of ligand are compared with the complexes confirming the complex formation. The shifting of bands from 3373 cm^-1 to 3341 cm^-1, decreases the C–N stretching frequency to 1373 cm^-1. The asymmetric and symmetric stretch of the COO^– is not present proposes that the COOH is present in the complex and the shift of C=O stretch (1673 cm^-1) proposes that oxygen of C=O is bonded with the M-O bond. The sharp band (1726 cm^-1) is shifted to a higher frequency proposing that the aliphatic acid group is not combined with the metal ion. The bands at 3783 cm^-1 indicate that both the hydroxyl group are present in the carboxylic acid. The new bands (605-575 cm^-1) Metal-Oxygen stretch and the band (557-527 cm^-1) are assigned to the M-N stretch of the complexes^14-16. 

Table 2: FT-IR data of the ligand and their five metal complexes.

Compound	ν O-H stretching for acid cm-1	ν C-O Aliphatic acid cm-1	ν C-O Aromatic acid cm-1	ν C–C   ring cm-1	ν C-N  stretching cm-1	ν N-H bending cm-1	ν M-O cm-1	ν M-N cm-1
Ligand	3373	1726	1705	1573	1398	1662	–	–
[Mn(L)2Cl2]2H2O	3436	1738	1670	1581	1384	1620	597	532
[Co(L)3]2+ [CoCl4]2-	3400	1737	1666	1575	1380	1624	605	527
[Ni(L)2Cl2]	3524	1740	1668	1578	1378	1610	605	527

L = Phenyl glycine o-carboxylic acid

Figure 2: Infrared Spectrum of Phenylglycine-o-carboxylic acid Ligand. Click here to View figure

Figure 3: Infrared Spectrum of Nickel(II) chloride Complex. Click here to View figure

Electronic Spectra of five metal Complexes

From the electronic spectral data the following assignment, structure and coordination of nickel, copper, and cobalt complexes were proposed which was listed in the table-3 ¹⁷.

Table 3: Electronic spectral data of three metal complexes.

Complex	Medium	Adsorption (nm)	Assignment	Stereochemistry
[Co(L)3]2+[CoCl4]2-	Methanol	651.78 nm 567 nm	15,342 cm-1 4A2 ® 4T1(P) 17,636 cm-1 4T1g ® 4T1g(P)	Tetrahedral and Octahedral
[NiL2Cl2]H2O	Ethanol	365.58nm	27,353 cm-1 3A2g ® 3T1g(P)	Octahedral
[CuL2Cl2]	Ethanol	712.83 nm	14,044 cm-1 2Eg ® 2T2g	Distorted octahedral

L = Phenylglycine-o-carboxylic acid

Figure 5: Electronic Spectra of (i) Cobalt(II) chloride, (ii) Nickel(II) chloride, (iii)Copper(II) Chloride complexes Click here to View figure

¹H NMR Spectral Studies.

The spectrum of the complex is taken in DMSO-D₆. The spectrum of ligand reveals different peaks at 6.48-7.82 ppm corresponding to aromatic proton¹³ and 3.94ppm corresponding to aliphatic CH₂ group 1.96 ppm due to NH group. The peak at 8.15 ppm assigns (2H) due to two carboxylic acid protons. In Zn(II) chloride complex shows different peaks at 6.53-7.84 ppm corresponding to an aromatic proton, 3.98 ppm corresponding to the aliphatic CH₂ group, and 2.50 ppm assigned to the NH group of secondary amine. The peak at 8.25 ppm responsible for -COOH (proton of carboxylic acid) attached to the aliphatic CH₂ group 12.6 ppm responsible for -COOH (proton of carboxylic acid) bonded to an aromatic ring. The movement in the position of that proton in the spectrum of the complex suggests that the electron density around the proton is changed because of coordination bond of –C=O (carbonyl oxygen) in the acid functionality.

Table 4: ¹H- NMR of ligand and the metal complex of Zn(II).

Compound	Aromatic proton (ppm)	CH2 group (ppm)	NH Group (ppm)	COOH group Aliphatic (ppm)	COOH group Aromatic (ppm)
Ligand	6.48-7.82	3.94	1.96	8.15	8.15
[ZnL2Cl2]	6.53-7.84	3.98	2.50	8.25	12.6

L = phenylglycine-o-carboxylic acid

Figure 6: 1H – NMR of Phenyl Glycine-O-Carboxylic acid. Click here to View figure

Figure 7: 1H NMR of Zinc (II) Chloride complex. Click here to View figure

Thermal Analysis

In Manganese(II) chloride complex, the curve depicts that the range between 100-120°C was due to the elimination of two lattice water molecules and loss of chloride around 230°C 16.1% (Cal 16.6%) assisted by an endothermic peak of about 136.1°C and 195.9°C in the DTA curve revealed that the complex melts before decomposition. Further, it decomposes from 300-570°C with a weight loss of 67.9% (calc 70%) corresponding to the decomposition of the ligand combined with an exothermic peak of 446°C on the DTA curve was observed. In Cobalt(II) chloride complex, it is stable up to 150°C^19,20. Above this temperature decomposes the cobalt(II) anion accompanied by an endothermic peak of 151.8°C on DTA showing melting of the complex. In the temperature range between 270-350°C, the anionic complex gets slowly decomposed, furthermore, the second stage of degradation occurs between the range of temperature from 350-580°C with 44.4% (cal 44.6%) mass loss and an exothermic peak with 441.7°C and 556.7°C on DTA are thereby, response to the ligand decomposition. The weight of cobalt oxide is estimated as19% (cal17.6%) are stable. The curve of the Nickel(II) chloride complex depicts an initial weight loss of  14.2% (calc 14.8%) at 50-200°C leads to the separation of one lattice water and non-coordinated ligand, an endothermic peak with 76°C on DTA depicts that there is an occurrence of melting of the complex. The second stage from 250-550°C with the gradual decrease of mass loss of 73.8% (calc 79.7%) corresponds to the removal of two chlorine atoms and the remaining part and an exothermic peak with 384.5°C and decomposition occurs at 512.9°C. The weight of the final residue is about 12% (calc 10.5%) corresponding to stable nickel oxide.

Figure 8: DTA and TGA Manganese (II) Chloride complex. Click here to View figure

Figure 9: DTA and TGA of Cobalt(II) Chloride complex. Click here to View figure

Figure 10: DTA and TGA curve of Nickel(II) chloride. Click here to View figure

Structure of the Complexes

Figure 11: Structure of metal(II) chloride complexes of phenyl glycine-O- carboxylic acid. Click here to View figure

Figure 12: Structure of [Co(L)3]2+[CoCl4]2- the complex of phenyl glycine-O-carboxylic acid. Click here to View figure

Electrochemical Behaviour

The electron transfer property of ligand and all the complexes were studied in DMF solution except cobalt(II) chloride complex. It was studied in methanol. All were recorded in 0.001M electrolytes in the range of –2 to +2 volt potential in the 50 mV/s scan rate except manganese(II) complexes. The manganese(II) chloride complex was scanned at about 20 mV/s.  The free ligand exhibits quasi reversible one-electron reduction at E_1/2 value is -0.907V (DE_p = 211 mV) and two irreversible oxidation potentials at E_pa 0.566V  and  1.221V. Manganese(II) chloride complex reveals the quasi reversible reduction²¹  with respect to Mn(II) ® Mn(I) at E_1/2 value of -0.765V (DE_p = 189mV). Cobalt (II) chloride complex reveals an irreversible reduction and two irreversible oxidation. The first irreversible reduction is allotted to metal-based Co(II) ® Co(I), two oxidative responses at (E_pa) = 0.738V and 1.536V were assigned to 2Co(II) ® 2Co(III) oxidation. Nickel(II) chloride complex exhibits irreversible reduction related to Ni(II) ® Ni(I), quasi reversible one-electron oxidation corresponding to Ni(II) ® Ni(III).   and it exhibits an irreversible oxidative response at (E_pa) = 1.349V assigned toNi(III) ® Ni(IV) oxidation. Copper(II) chloride complex displays quasi reversible one-electron reduction²² with respect to Cu(II) ®  Cu(I) at E_1/2 value of -0.842V (DE_p = 200 mV) and it exhibits an irreversible oxidative reduction at E_pc =0.0108V.The Zinc(II) chloride exhibits quasi reversible one-electron reduction concerning Zn(II) ® Zn(I) at an E_1/2 value of -0.781V (DE_p = 161 mV). From the results, it is conclude that, the metal complexex zinc, copper and manganes are quasi reversible reduction, the reduction waves with E_1/2  in the range of 0.765V to 0.842V is assigned to M(II) ® M(I) reduction, Ni(II) complex exhibits quasi reversible oxidation and Cobalt (II)complex exhibits irreversible reduction and oxidation. The potentials are summarized in table 5.

Figure 13: CV of Cobalt(II) chloride complex. Click here to View figure

Figure 14: CV of Copper(II) chloride complex. Click here to View figure

Figure 15: CV of Zinc(II) chloride complex. Click here to View figure

Table 5: Cyclic voltammetry of Metal(II) complexes of PGA.

Complexes	Reduction				Oxidation
	Epa (V)	Epc (V)	E1/2 (V)	DEp (mV/s)	Epa (V)	Epc (V)	E1/2 (V)	DEp (mV/s)
Ligand	-0.8022	-1.014	-0.908	211	0.566 1.236	–	–	—
[Mn(L)2Cl2]2H2O	-0.6707	-0.8603	-0.765	189	–	–	–	–
[Co(L)3]2+ [CoCl4]2-	–	-1.229	–	–	0.7381 1.536	–	–	–
[Ni(L)2Cl2]	–	-0.7618	–	–	0.721 1.349	0.217	0.884	504
[Cu(L)2Cl2]	-0.7420	-0.9426	-0.842	200	–	0.0108	–	–
[Zn(L)2Cl2]	-0.6991	-0.8636	-0.781	161	–	–	–	–

L = Phenyl glycine o-carboxylic acid

Biological Activity

Antifungal activity

The antifungal activities of three metal complexes and their ligand has been examined was inimical to 3 fungal pathogens – Aspergillus niger, Aspergillus flavus, and Aspergillus terreus by the Agar well diffusion method, and the outcomes are validated and tabulated in table 6

Table 6: Antifungal activity of Metal(II) chloride complexes.

Compound	Zone of inhibition (mm)
	Aspergillus niger	Aspergillus flavus	Aspergillus terreus
Ligand (PGC)	10	6	–
[Co(L)3]2+ [CoCl4]2-	5	3	19
[Ni(PGC)2Cl2 ]	10	–	10
[Cu(PGC)2Cl2]	–	–	15

 

Figure 16: Antifungal activity of Metal(II) chloride complexes Click here to View figure

Antifungal activity of ligand compared with their metal(II) chloride complexes. The ligand has no activity against Aspergillus terreus, but copper, nickel and cobalt complexes showed good activity against Aspergillus terreus. Cobalt(II) complex reveals a better activity inimical to  Aspergillus niger and Aspergillus flavus.

Antibacterial activity

Phenyl glycine-o-carboxylic acid and its complexes have been examined by the growth of bacteria such as Klebsiella pneumonia, Escherichia coli, Bacillus anthrax, and Staphylococcus aureus. The ligand has no activity against Klebsiella pneumonia.

Table 7: Antibacterial activities of three Metal(II) chloride complexes and the ligand.

	Zone of inhibition (mm)
	K pneumonia	E. coli	Bacillus anthrax	S. aureus
Ligand (PGC)	–	8	18	20
[Co(L)3]2+ [CoCl4]2-	13	20	25	20
[Ni(PGC)2Cl2]	10	13	20	20
[Cu(PGC)2Cl2]	12	25	25	4

 

Figure 17: Antibacterial activity of Metal(II) chloride complexes. Click here to View figure

The ligand phenyl-glycine -o- carboxylic acid and their selected metal complexes depict a moderate activity inimical to B.anthrax. The metal complexes show fair activity against E.coli. The copper complex shows less activity against S.aureus. From the above outcomes, it is concluded that the phenyl-glycine -o- carboxylic acid and its metal complexes manifest a good activity inimical to the growth of various microorganisms.

Conclusion

The Phenyl glycine -O- carboxylic acid and its complexes has been concocted and signalized that the ligand is employed as a bidentate, where the carbonyl oxygen and nitrogen of the secondary amine are bound to the metal ion. The electrical conductance analysis illustrates, that the cobalt complex is in a 1:1 electrolyte. ¹H NMR spectral study elucidates that; the hydroxyl group of the carboxylic acid is not ionized. Remarkably, CV studies manifest that manganese(II), Copper(II) and Zinc(II) complexes flourish in a quasi reversible one-electron transfer reduction process whereas, the Cobalt(II)and Nickel(II) complexes flaunt an irreversible reduction and oxidation process. The ligand and the complexes make evident that it has a good antimicrobial activity inimical to the fungal and bacterial strains.

Conflict of Interest

There is no conflict of interest.

Funding Sources

There is no funding source.

Acknowledgement

Both the authors thank the Sastra University, Thanjavur, and CECRI Karaikudi for their technical assistance.

References

1. Taghreed, H.; Al-Noor; Halid Ali, F.; Amer Jarad, J.; and Alica Kindeel, S.; Synthesis, Spectral and antimicrobial activity of mixed ligand complexes of Co(II), Ni(II), Cu(II), and Zn(II) with Anthranilic acid and Tributy phosphine, Chemistry and Research, ISSN2225-0956,Vol. 3, No. 3, 2013.
2. Nasser Mohammed Hosny; Synthesis, characterization and optical band gap of NiO nanoparticles derived from anthranilic acid precursors via a thermal decomposition route; Polyhedron 30, 2011, 470–476.
   CrossRef
3. Xiaomeng Zhou; Qing Wang; Weihua Zhao; Songsong Xu; Wei Zhang and Junmin Chen; Palladium-catalyzed ortho-arylation of benzoic acid derivatives via C–H bond activation using an aminoacetic acid bidentate directing group Tetrahedron Letters; 2015, 851–855.
   CrossRef
4. Jing-Wei Zheng; and  Lin Ma; Metal complexes of anthranilic acid derivatives: A new class of non-competitive α-glucosidase inhibitors Chinese Chemical Letters, Volume 27, Issue 5, May 2016, Pages 627–630.
   CrossRef
5. Saleem Raza; Yousaf Iqbal Hussian; Muslim raza; Syed Uzair Ali Shah; Ajmal Khan; Raheela Taj and Abdur Raul; Synthesis of Anthranilic Acid and Anhydride Ligand and their Metal Complexes, Biochemistry & Analytical Biochemistry, 2013, 2, 3.
6. Prakash.V.; and Suresh, M.; Preparation Characterization, ¹H, ¹³C NMR Study and Antibacterial Studies of Schiff Bases and Their Zn(II) Chelates, Research Journal of Pharmaceutical, Biological and Chemical Sciences, Volume 4 Issue 4, 2013, Pg.1536.
7. Frank Wiesbrock and Hubert Schmidbaur; Interactions of a b-dipeptide with mono-valent metal cations: crystal structures of (anthranoyl) anthranilic acid and its lithium, sodium and thallium salts, Journal of Inorganic Biochemistry 98, 2004, 473–484.
   CrossRef
8. Subrahmaniansupriya; Aravamudhan Raghavan; Vijayaraghavan; Mannich; amino methylation reactions of a series of bis (a-amino acid ato) metal(II) complexes with formaldehyde and dimethyl malonate, Science direct polyhedron 26, 2007, 3217-3226.
   CrossRef
9. Venkateswara Rao, P.V.; Prasad, A.V.G.S.; and Prasad, P.S.; Novel synthesis, characterization and antimicrobial screening of Schiff base complex, International Journal of Pharmacy, 4(4), 2014, 215-218.
10. Md. Rabicel Hasan; Mohammad Amzad Hossain; Md.Abdus Salam; Mohammad Nasir Uddin; Nickel complexes of Schiff bases derived from mono/diketone with anthranilic acid: Synthesis, characterization and microbial evaluation, Journal of Taibah university for science 10, 2016, 766-773.
    CrossRef
11. Iqbal, J.; Imran Iqbal, M.; Sand Latif, S.; Synthesis, Characterization and Biological studies of 2-[phenylmethylamino] benzoic acid and its complexes with Co(II), Ni(II), Cu(II), Zn(II), Jour. Chem. Soc. Pak. Vol.29, 2007, No.2
12. Geary, W.J.; Coord. Chem. Rev. 7, 1971, 81.
    CrossRef
13. Donald Pavia, L.; Gary Lampman, M.; George Kriz, S.; Introduction to Spectroscopy, Third edition, Western Washington University.   
14. Kazuo Nakamoto; Infrared and Raman Spectra of Inorganic and Coordination compounds4th Ed.; John Wiley and Sons, Inc.: New York, 1986.
15. Ali Riyahee, A.A.AL.; Hanaa Hadadd, H.; and Baydaa Jaaz, H.; Novel Nickel(II),Copper(II),and Cobalt(II) complexes of Schiff bases A,D and E: Preparation Identification, Analytical and Electrochemical Survey, Oriental Journal of chemistry , ISSN:0970-020X,  Vol34, 2018, No. g. (6): P2927-2941.
    CrossRef
16. Nicholis, D.; Complexes and First Row Transition Elements, the Macmillan Press: G. Britain, 1979, 52.
17. Lever, A.B.P.; Inorganic Electronic Spectroscopy, second., Elsevier, Amsterdam, 1984.
18. Herrera, A.M.; Staples, R.J.; Kryatov, S.V.; Nazarenko, A.Y.; Akimova, E.V.; Nickel(II)  and copper(II) complexes with pyridine-containing macrocycles bearing an aminopropyl pendant arm: synthesis, characterization, and modifications of the pendant amino group, J. Chem. Soc. Dalton Trans, 2003, 846–856.
    CrossRef
19. Dash, D.C.; Panda, A.K.; Jena, P.; Patjoshi, S.B.; Mahapatra, A, J.; Indian Chem. Soc. 79, 2002, 48.
    CrossRef
20. Tamilarasu Ezhilarasu; Anbazhagan Sathiyaseelan; Pudupalayam; Thangavelu;     Kalaichelvan  and  Sengottuvelan Balasubramanian; Synthesis of 40-substituted-2,20;60,200-terpyridine Ru(II) complexes electrochemical, fluorescence quenching and antibacterial studies, Journal of Molecular Structure 1134, 2017, 265-277.
    CrossRef
21. Bibhesh Singh, K.; Parashuram Mishra; Anant Prakash Narendar Bhojak; Spectroscopic, electrochemical and biological studies of the metal complexes of the Schiff base derived from pyrrole-2-carbaldehyde and ethylenediamine, Arabian Journal of Chemistry, 2017, 10, S427-S483.
    CrossRef
22. Muhammad Shabbir; Zareen Akhter; Iqbal Ahmad; Safeer Ahmed; Vickie McKee; Hammad Ismail and Bushra Mirza; Copper (II) complexes bearing ether based on donor bidentate Schiff bases: Synthesis, characterization, biological and electrochemical investigations; Polyhedron 124, 2017, 117–124.
    CrossRef

---

This work is licensed under a Creative Commons Attribution 4.0 International License.