Transition Metal Tetrahydro-Salophen Type Complexes: Synthesis, Characterization and Antitubercular Studies

 

Udaysinha Patil¹, Mustapha Mandewale^1*, Bapu Thorat¹, Aarti Nagarsekar¹, Ramesh Yamgar²

¹P.G. and Research Laboratory, Department of Chemistry, Government of Maharashtra, Ismail Yusuf College of Arts, Science and Commerce, Jogeshwari (East) Mumbai-400 060, India.

²Department of Chemistry, Chikitsak Samuha’s Patkar-Varde College of Arts, Science and Commerce, Goregaon (West), Mumbai 400 062, India.

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

A series of tetrahydrosalophen Schiff bases have been prepared from the reaction of two equivalents of salicylaldehyde with one equivalent o-phenylenediamine derivatives followed by reduction with NaBH_4. The Co (II), Ni (II), Cu (II) and Zn (II) complexes of these ligands have been prepared. All the synthesized ligands and metal complexes were characterized by IR, ¹H and ¹³C-NMR, MS, XRD, TGA, UV-Visible, Fluorescence and elemental analysis. The Preliminary results of antituberculosis study showed that the salophen schiff bases 2a-2b demonstrated very good antituberculosis activity while the tetrahydrosalophen schiff bases 3a-3i showed moderate activity. Among the tested metal complexes 4a was found to be most active with minimum inhibitory concentration (MIC) of 6.25 μg/ml against Mycobacterium tuberculosis (H37 RV strain) ATCC No- 27294.  

 

1. INTRODUCTION:

The salophen-type ligands present versatile steric, electronic and lipophilic properties. They may be easily prepared by the condensation of an aromatic o-hydroxybenzaldehyde and a diamine. Salophen-type ligands with N and O atoms are important as their metal complexes show extensive applications in a variety of reactions as homogeneous catalysis [1-2], Oxidation [3], hydroxylation [4], Epoxidation [5], Polymerization [6], Hydrogenation [7]. These compounds also found applications as electroluminescent materials [8-9], optical devices [10], electrochemical sensors [11], antifungal [12] and antimicrobial activity [13].

 

In solution, Schiff base ligands have the disadvantage of their tendency of hydrolysis. This instability can be conquered by reduction of the Schiff base to give an amine. This presents interesting possibilities since the reduced Schiff base will be more flexible and not forced to remain planar when coordinated to a metal centre. Sodium borohydride is a common reducing agent and widely used in organic synthesis. There are a number of reports available for application of sodium borohydride in reduction of imines (schiff bases) [14-15].

 

 

FIGURE 1: Previously reported schiff bases as anti-tuberculosis agents and target compounds.

 

 

Recently it is reported that reduced schiff base (I) Fig. 1 showed significant antimicrobial activity at low micromolar level [16]. Among the ligand systems, salophen derivatives are highly important because, these ligands developed due to their varied chelating ability, catalytic activities and structural flexibility. Voronova et al. [17] reported excellent catalyst for the Sonogashira coupling reaction (II) Fig. 1. Further, various types of reduced schiff base ligands and their Fe complexes (III) Fig. 1 have attracted continued interest in the medicinal field due to their effective DNA clevage activity [18]. It is evident from the literature that transition metal complexes of partialy reduced schiff base scaffolds (IV) Fig. 1 are known to exhibit excellent catalyst for oxidation of various phenols [19].

Based on information gathered from literature and in continuation of our research for new antitubercular agents [20-22], we have started research studies on synthesis and antituberculosis screening of some new transition metal complexes of salen type ligands shown in Fig. 1.

 

2. EXPERIMENTAL:

2.1 General

All the chemicals and solvents used were purchased from Sigma Aldrich. NMR spectra were recorded on the Varian-NMR-Mercury 300 MHz instruments. Infrared spectra were obtained using IR-7600 Lambda Scientific Pty. Ltd. Instrument. UV–Visible and fluorescence spectra were recorded on Shimadzu UV-1800 spectrophotometer and Shimadzu RF-5301pc respectively. The DSC-TGA analysis was processed on Universal V4.5A TA instrument. The molar conductivity of the chelates were measured using DMSO solvent.

 

2.2 General procedure for preparation of schiff bases

A solution of salicylaldehyde (4 mmol) and 1,2-diamine derivative 1a-1b (2.0 mmol) in EtOH (8 mL) was stirred for 2 hr. After completion of the reaction the solid obtained was filtered and dried (see Fig. 2 and Table 1).

 

2.2.1 Preparation of 2,2'-{1,2-phenylenebis [azanylylidene(E)methanylylidene]}diphenol [2a]

M.P.: 154-156 ⁰C; Colour: Yellow; MS [M+2]: 318.22; IR(KBr cm^-1): 3056, 2734, 1614, 1562, 1481, 1363, 1276, 1191, 977, 910, 759; ¹H NMR (300 MHz, DMSO-d₆) δ: 6.930-6.978(m, 4H), 7.398-7.430(m, 4H), 7.635-7.658(m, 4H), 8.916(s, 2H), 12.904(s, 2H);; ¹³C NMR (75MHz, DMSO-d₆) δ: 162.2, 162.1, 161.3, 161.1, 136.3, 136.2, 132.4, 132.3, 131.9, 131.7, 129.2, 129.1, 124.3, 124.2, 119.3, 119.2, 119.1, 119.1, 117.3, 117.1; Elemental analysis [C₂₀H₁₆N₂O₂]: observed (calculated): C 75.79% (75.93%), H 5.15% (5.10%), N 8.94% (8.86%).

 

2.2.2 Preparation of 2,2'-{(4-methyl-1,2-phenylene)bis[azanylylidene(E)methanylylidene]} diphenol [2b]

M.P.: 165-167 ⁰C; Colour: Yellow; MS [M+H]: 331.43; IR(KBr cm^-1): 3054, 2985, 2917, 2713, 1616, 1563, 1486, 1365, 1278, 1189, 950, 757, 638; ¹H NMR (300 MHz, DMSO-d₆) δ: 2.389(s, 3H), 6.936-6.973(m, 4H), 7.204-7.282(m, 2H), 7.379-7.405(m, 3H), 7.630-7.677(m, 2H), 8.927(s, 2H), 12.950(s, 1H), 13.070(s, 1H); ¹³C NMR (75MHz, DMSO-d₆) δ: 162.3, 162.1, 161.2, 161.1, 136.3, 136.2, 132.4, 132.4, 132.3, 131.8, 131.7, 126.1, 125.1, 124.5, 119.2, 119.2, 119.1, 119.1, 117.3, 117.1, 21.2; Elemental analysis [C₂₁H₁₈N₂O₂]: observed (calculated): C 76.40% (76.34%), H 5.41% (5.49%), N 8.55% (8.48%).

 

2.3 General procedure for preparation of reduced schiff bases

To a solution of the schiff base (2.27 mmol) in dichloromethane (10 mL) at 0°C was added a methanolic solution of NaBH₄ (2.0 mmol) containing some drops of concentrated KOH solution. The pH was set to 6 and the solution stirred. After completion of the raction, solvent was removed by distillation. Then 10 mL cold water was added to the residue. The pH was set to 4–5 by using of 3M HCl. The white solid obtained was isolated by filteration. The structure of target compounds is represented in Fig. 2 and Table 2.

 

2.3.1 Preparation of 2,2'-[1,2-phenylenebis (azanediylmethylene)]diphenol [4a]

M.P.: 132-134 ⁰C; Colour: White; MS [M+]: 320.13; IR(KBr cm^-1): 3394, 3359, 3289, 3041, 2852, 1696, 1456, 1315, 1238, 1103, 1025, 929,750, 636; ¹H NMR (300 MHz, DMSO-d₆) δ: 4.236(s, 4H), 5.068(s, 2H), 6.37-6.450(m, 3H), 6.758-6.843(m, 3H), 7.023-7.070(m, 3H), 7.176-7.222(m, 3H), 10.805(s, 2H); ¹³C NMR (75MHz, DMSO-d₆) δ:  157.6, 157.5, 141.1, 141.0, 131.8, 131.8, 128.9, 128.8, 123.2, 123.1, 122.6, 122.6, 121.8, 121.8, 120.6, 120.6, 116.1, 116.0, 45.9, 45.8; Elemental analysis [C₂₀H₂₀N₂O₂]: observed (calculated): C 75.04% (74.98%), H 6.32% (6.29%), N 8.77% (8.74%).

 

2.3.2 Preparation of 2,2'-[(4-methyl-1,2-phenylene) bis(azanediylmethylene)]diphenol [4b]

M.P.: 125-127 ⁰C; Colour: White; MS [M+H]: 335.57; IR(KBr cm^-1): 3390, 3359, 3278, 2852, 1696, 1455, 1305, 1251, 1110, 935,844, 800, 752; ¹H NMR (300 MHz, DMSO-d₆) δ: 2.055(s, 3H), 4.191(s, 4H), 4.987(s, 2H), 6.267-6.385(m, 2H), 6.655-6.818(m, 5H), 7.024(m, 2H), 7.172-7.195(m, 2H), 12.666(s, 1H), 12.904(s, 2H); ¹³C NMR (75MHz, DMSO-d₆) δ:  157.6, 157.5, 141.1, 134.7, 132.9, 131.9, 131.8, 128.9, 128.8, 124.2, 123.2, 123.1, 120.7, 120.5, 118.8, 116.2, 116.1, 114.9, 45.9, 45.8, 21.2, Elemental analysis [C₂₁H₂₂N₂O₂]: observed (calculated): C 75.34% (75.42%), H 6.72% (6.63%),  N 8.30% (8.38%).

 

2.4 General procedure for preparation of metal complexes

The ligand (0.050 mmol) was dissolved in 15 ml of methanol. Corresponding metal salt (CuCl_2, NiCl₂, CoCl₂, ZnCl₂) (0.050 mmol) was added and stirred the reaction mixture, finally Potassium hydroxide (0.050 mmol) in methanol was added and reaction mixture was refluxed for 3-5 hours in water bath. The product obained upon cooling was filtered and dried Fig. 2 and Table 3.

 

 

Figure 2: Preparation of target ligands and their metal complexes

TABLE 1: Structures of schiff bases 2a-2b and reduced schiff bases [3a-3b]

TABLE 2: Structures of metal complexes of schiff bases [4a-4h]

 

TABLE 3: Structures of metal complexes of reduced schiff bases [5a-5h]

 

3. RESULTS AND DISCUSSION:

3.1 Chemistry

The target transition metal complexes (4a-4h and 5a-5h) were synthesized as depicted in Fig. 2. The first step involves the synthesis of schiff base derivatives by condensation of salicylaldehyde with diamines 1a-1b in warming ethanol at 70⁰ C afforded schiff bases 2a-2b. On treatment with sodium borohydride imine bond undergo reduction yield reduced schiff base ligands 3a-3b. Elemental analyses and spectral data (FT-IR, ¹H and ¹³C-NMR, MS, UV-Visible and Fluorescence) confirmed the structure of the synthesized products. The FT-IR spectrum of schiff bases 2a-2b showed strong absorption bands at 1614-1616 cm^-1 due to imine (-HC=N-) function, which diappears in the IR spectra of reduced schiff bases 3a-3b confirms the reduction of schiff bases 2a-2b. IR spectra of reduced schiff base ligands 3a-3b showed broad peak in the region 3390-3394 cm^-1 and 3359 cm^-1 due to amino (-NH-) and hydroxyl group, respectively. The ¹H-NMR spectrum of schiff bases 2a-2b revealed, in addition to expected aromatic signals, three singlets at δ 8.91 and 12.95 ppm are assignable to the azomethine proton (-CH=N-) and hydroxyl proton (-OH), respectively. The new singlets at δ 4.2 and 4.9 due to –CH₂- and –NH- group, respectively confirms the formation of reduced schiff bases 3a-3b. In addition, the ¹³C-NMR spectrum of schiff bases 2a-2b displayed characteristic peaks at δ 161.5 ppm assignable to imine carbon, which disappear from the spectra of 3a-3b. Moreover the mass spectrum of schiff bases revealed molecular ion peak confirming corresponding molecular weight of target compounds.

 

The schiff bases 2a-2b and reduced schiff base ligands 3a-3b were refluxed with appropriate transition metal chlorides in methanol with molar ratio 1:1 offer metal complexes 4a-4h and 5a-5h respectively. All metal complexes show broad peak in the region of 3330-3517 cm­­^-1 due to water of crystallization. The coordination approach of hadrazone with central metal ion can be elucidated on the basis of IR spectral study. The low frequency region of the spectra indicated the presence of two new medium intensity bands at about 443-485 cm⁻¹ due to υM–O vibrations. The IR spectra of all the metal complexes show prominent band at about 501-620 cm−1 due to υM–N stretching. Elemental analysis of the metal complexes is in good agreement with the theoretical values as shown in Table 4.

Table 4: Molar conductance (Λm) and % content of metal in complexes

Complex	Metal	% Metal Observed (Calculated)	Molar conductance Λm (Ω−1 mol−1 cm2)
4a	Cu	16.90(16.82)	11.32
4b	Ni	15.70(15.73)	10.01
4c	Co	15.84(15.79)	9.87
4d	Zn	17.30(17.22)	10.21
4e	Cu	16.14(16.21)	11.72
4f	Ni	15.18(15.16)	10.29
4g	Co	15.30(15.22)	9.83
4h	Zn	16.66(16.61)	6.40
5a	Cu	16.60(16.64)	11.24
5b	Ni	15.63(15.57)	10.81
5c	Co	15.58(15.62)	9.10
5d	Zn	16.96(17.04)	7.30
5e	Cu	16.09(16.05)	10.96
5f	Ni	14.93(15.01)	11.40
5g	Co	15.01(15.06)	9.56
5h	Zn	16.39(16.44)	7.11

 

The conductivity study show negligible molar conductance values as shown in table 4, indicating that the complexes are non-electrolytes. The thermal behavior of the metal complex 5d Fig. 3 was studied in temperature range of 25⁰–1000⁰ C. The TG-DTA studies of complex 5d show that the decomposition involves three steps. In the first stage (below 100⁰ C) weight loss corresponds to the presence of the lattice cell water in the complexes. Second step involves weight loss in the temperature range 110⁰–200⁰ C is due to elimination of coordinated water. A plateau was observed above 600⁰ C corresponds to the formation of stable zinc oxide.

 

Figure 3: The TGA/DSC of [5d]

 

Figure 4: The XRD spectrum of [5d]

 

The X-ray powder diffraction data provide fundamental structural information of materials which do not yield single crystals of good quality. We could not prepared Single crystals of the complexes under study therefore the powder diffraction data were acquired for structural description [23]. The X-ray diffractogram of the ligand and the complexes were measured in the range of 5⁰ to 70⁰ 2θ values, which are shown in the Fig. 4. The XRD pattern indicates that complex 5d have well defined crystalline patterns, with various degrees of crystallinity.

 

The practical observations are in good agreement with the theoretical values calculated for 1:1 ratio of metal:ligand stoichiometry. The above explanation of the results of various spectroscopic details it may be concluded that the proposed geometry for the transition metal complexes with general formula ML⋅2H₂O is octahedral for metal complexes. The proposed structures are shown in table 2 and table 3.

 

3.2 Anti-tuberculosis evaluation

The anti-tubercular activity of the synthesized ligands and their metal complexes against Mycobacterium tuberculosis (H37 RV strain) ATCC No- 27294, were assessed at the Deparment of Microbiology, Maratha Mandal’s NGH Institute of Dental Sciences and Research Centre, Belgaum-590010, India. The method applied is similar to that reported by Maria and Lourenco [24]. Ciprofloxacin (MIC 3.12 𝜇g/mL), Pyrazinamide (MIC 3.12 𝜇g/mL) and Streptomycin (MIC 6.25 𝜇g/mL) were used as references to evaluate the potency of the synthesized compounds. As shown in table 5 compounds 4a has unpredictable high anti-tuberculosis activity against Mycobacterium tuberculosis as its MIC value is 6.25 µg/mL, which is comparable to antimicrobial potency of Streptomycin. This could be due to formation a specific complex with cell wall protein and eventually interfering in cell wall synthesis of Mycobacterium tuberculosis during cell mitosis phase of multiplication. The presence of active pharmacophore present in the molecular structure of the ligand, like imine double bond between carbon and nitrogen and well positioned hydroxyl group, these functional groups might interfere in the mechanism of cell mitosis and hence stop further growth of Mycobacterium tuberculosis. All the studied samples are showing dissimilar potency due to the effective barrier of cell wall membrane of Mycobacterium tuberculosis for entrance of external substances like test compounds under this study. However, reduced schiff bases 3a-3b showed less activity than their unreduced form 2a-2b.

 

The metal complexes of 4a, 4e and 5a have shown greater antituberculosis activity than its parent ligand. This finding indicates that complex formation enhanced their penetration into the cell wall of the Mycobacterium tuberculosis, which translated into better activity. In addition, these compounds disturb the respiration process of the cell and thereby restrict the synthesis of proteins. If the synthesis of proteins is blocked then formation bacterial cell wall is not possible which ultimately results in cell death and therefore restricts further growth and infection of the bacteria [25].

 

Table 5: Showing comparative anti-tuberculosis screening results by MIC method

Test Sample	Sample concentration in 𝜇g/mL (MIC)	Test Sample	Sample concentration in 𝜇g/mL (MIC)
2a	12.5	3a	25
4a	6.25	5a	12.5
4b	25	5b	25
4c	12.5	5c	25
4d	50	5d	25
2b	25	3b	50
4e	12.5	5e	25
4f	50	5f	50
4g	50	5g	50
4h	50	5h	50

 

According to one more possible mechanism, these schiff bases might be interacting with the DNA gyrase enzyme, which is essential for DNA multiplication step. The metal complexes inhibite DNA gyrase, which alter the multiplication of bacterial cells, eventually resulting death of the bacteria [26-29]. The observed results of the test compounds indicates the future potential for the development of metal coordination complexes to solve the limitations due to currently existing anti-tuberculosis agents to treat multiple drug resistant Tuberculosis.

 

3.3 Fluorescence Study:

The UV-Visible spectra of the ligands 2a-2b and 3a-3b exhibit bands around 332-336 nm and 302-307 nm respectively as represented in Fig. 5. The broad, intense band around 310 nm in the ligands 2a-2b can be assigned to intra ligand n–π* transition associated with the azomethine linkage which is not observed for ligands 3a-3b. The bands at around 298-370 nm are attributed to the ligand to metal charge transfer transitions Fig. 6 and Fig. 7.

 

 

 

Table 6: The absorption and emission wavelength with intensity

 

The emission spectra of ligands 2a-2b Fig. 8 showed the emission band in the range of 461-463 nm while ligands 3a-3b showed strong emission at 360 nm. The complexes 4a-4h Fig. 9 Table 6 showed emission band in the range of 378-516 nm. The complexes 5a-5h Fig. 10 Table 6 showed emission band in the range of 431-516 nm. The Zn (II) complexes demonstrated intense fluorescent properties as compared their parent ligands as well as other metal complexes. The incorporation of metal effectively increases the conformational rigidity of the structures of ligand and increases the fluorescence intensities of the complexes, which shows that it is good material in photochemical applications of these complexes.

 

 

Figure 5: Electronic spectra of 2a-2b	Figure 6: Electronic spectra of 4a-4h
Figure 7: Electronic spectra of 5a-5h	Figure 8: Fluorescence spectra of 2a-2b and 3a-3b
Figure 9: Fluorescence spectra of 4a-4h	Figure 10: Fluorescence spectra of 5a-5h

 

 

4. CONCLUSIONS:

Based on the results and discussion, it is concluded that the complexes have 1:1 metal to ligand stoichiometry. Coordination behavior of schiff base and reduced schiff base ligands is in tetradentate manner which is evidenced by the elemental analysis and the spectral data. The metal complexes have higher antituberculosis activity than their parent ligand; especially Co (II) complexes have shown more activity even at the MIC level. The Zn (II) complexes exhibited very good fluorescence properties. This study would pave the way for future development of more effective terahydrosalophen analogs for biological and material applications.

 

5. ACKNOWLEDGMENTS:

The authors thank Principal and Head Department of Chemistry, Government of Maharashtra, Ismail Yusuf Arts, Science and Commerce College for providing research and library facilities. The authors also thank Dr. Kishore Bhat of Governmental Dental College, Belgaum, for facilitating anti-TB assays and providing the procedure for the same.

 

6. REFERENCES:

[1]            R. Bolton, T.N. Danks and J.M. Paul. Preparation and reduction of some camphor imines. Tetrahedron Letters. 35; 1994:411-3412.

[2]            Foad Kazemi, Ali Reza Kiasat and Ebrahim Sarvestani. Practical reduction of imines by NaBH₄/alumina under solvent-free conditions: An efficient route to secondary amine. Chinese Chemical Letters. 19; 2008:1167–1170.

[3]            T. Uchida and T. Katsuki. Cationic Co(III)(salen)-catalyzed enantioselective Baeyer–Villiger oxidation of 3-arylcyclobutanones using hydrogen peroxide as a terminal oxidant. Tetrahedron Letters. 42; 2001:6911-6914.

[4]            A.G.J. Ligtenbarg, E.K. Beuken, A. Meetsma, N. Veldman, W.J.J. Smeets, A.L. Spek and B.L. Feringa. New mono- and di-nuclear complexes of PdII, PtII and NiII of PNNP ligands with a 2,2′-biaryl bridging unit. Journal of Chemical Society Dalton Transactions. 1998:263-270.

[5]            E.M. McGarrigle and D.G. Gilheany. Chromium and Manganese salen Promoted Epoxidation of Alkenes, Chemical Reviews. 105; 2005:1563-1602.

[6]            B.J. Coe, J.A. Harris, B.S. Brunschwig, I. Asselberghs, K. Clays, J. Garin, J. Orduna. Three-dimensional nonlinear optical chromophores based on metal-to-ligand charge-transfer from ruthenium (II) or iron (II) centersJournal of American Chemical Society, 127 (2005) 13399-13410.

[7]            Y. Nishibayashi, I. Takei, S.Vemara and M. Hidai. Extremely High Enantioselective Redox Reaction of Ketones and Alcohols Catalyzed by RuCl2(PPh3) (oxazolinylferrocenylphosphine). Organometallics. 18; 1999:2291-2293.

[8]            T. Yu, W. Su, W. Li, Z. Hong, R. Hua and B. Li. A schiff base zinc complex and its electroluminescent properties. Thin solid Films. 515; 2007:4080-4084.

[9]            Y. Yi, X. Q. Wei, M.G. Xie and Z.Y. Lu. Synthesis and color-tunable fluorescence properties of schiff base zinc (II) complexes used as electroluminescent materials. Chinese Chemical Letters. 15; 2004:525-528.

[10]         T. Verbiest, S. Houbrechts, M. Kauranen, K. Clays, A. Persoons. Second-order nonlinear optical materials: recent advances in chromophore design, Journal of Material Chemistry, 7 (1997) 2175-2189.

[11]         T. Shamspur, I. Sheikhshoaie and M.H. Mashhadizadeh. Flame atomic absorption spectroscopy (FAAS) determination of iron (III) after preconcentration on to modified analcime zeolite with 5-((4- nitrophenylazo)-N-(2′,4′-dimethoxyphenyl))salicylaldimine by column method. Journal of Analytical Atomic Spectrometry.  20; 2005:476-478.

[12]         G.B. Bagihalli, P.G. Avaji, S.A. Patil and P.S. Badami. Synthesis, spectral characterization, in vitro antibacterial, antifungal and cytotoxic activities of Co(II), Ni(II) and Cu(II) complexes with 1,2,4-triazole Schiff bases. European Journal of Medicinal Chemistry. 43; 2008:2639-2649.

[13]         E. Keskioglu, A.B. Gunduzalp, S. Cete, F. Hamurcu and B. Erk. Cr (III), Fe (III) and Co (III) complexes of tetradentate (ONNO) Schiff base ligands: Synthesis, characterization, properties and biological activity. Spectrochimica Acta Part A. 70; 2008:634–640.

[14]         B.T. Cho and S.K. Kang, Clean and Simple Chemoselective Reduction of Imines to Amines Using Boric Acid-Activated Sodium Borohydride under Solvent-Free Conditions. Synlett. 9; 2004:1484-1488. DOI: 10.1055/s-2004-829066

[15]         B.T. Cho, S.K. Kang, Direct and indirect reductive amination of aldehydes and ketones with solid acid-activated sodium borohydride under solvent-free conditions. Tetrahedron. 61; 2005:5725-5734.

[16]         Musiliyu A. Musa, M. Omar F. Khan, Arden Aspedon and John S. Cooperwood. Synthesis and Antimicrobial Activity of N,N′-Bis(2-hydroxylbenzyl)-1,2-ethanediamine Derivatives. Lett Drug Des Discov. 7(3); 2010:165–170. DOI: 10.2174/157018010790596678

[17]         Krisztina Voronova, Levente Homolya, Antal Udvardy, Attila C. Benyei and Ferenc Jo, Pd–Tetrahydrosalan-Type Complexes as Catalysts for Sonogashira Couplings in Water: Efficient Greening of the Procedure. ChemSusChem.  DOI: 10.1002/cssc.201402147

[18]         Sylvain Routier, Herve Vezin, Eric Lamour and Christain Bailly. DNA cleavage by hydroxy-salicylidene-ethylendiamine-iron complexes, Nucleic Acids Research. 27(21); 1999: 4160-4166.

[19]         Waldermar Adam, Chantu Saha-Moeller and Pralhad Ganeshpure. A convevient synthesis of nickel (II) and cobalt (II) complexes of unsymmetrical salen-type ligands and their applications as catalysts for the oxidation of 2,6-dimethylphenol and 1,5-dihydronaphthalene by molecular oxygen. Indian Journal of Chemistry. 43A; 2004:56-62.

[20]            Mustapha C. Mandewale, Bapu R. Thorat, D. Shelke, Ramesh S. Yamgar. Synthesis and biological evaluation of new hydrazone derivatives of quinoline and their Cu (II) and Zn (II) complexes against Mycobacterium Tuberculosis. Bioinorganic Chemistry and Applications. 2015. DOI:http://dx.doi.org/10.1155/2015/153015

[21]            Mustapha C. Mandewale, Bapu R. Thorat, and Ramesh S. Yamgar. Synthesis and anti-mycobacterium study of some fluorine containing Schiff bases of quinoline and their metal complexes.  Der Pharma Chemica. 7; 2015:207-15.

[22]            Ramesh Yamgar, Y. Nivid, Satish Nalawade, Mustapha Mandewale, R. G. Atram and Sudhir Sawant. Novel Zinc (II) Complexes of Heterocyclic Ligands as Antimicrobial Agents: Synthesis, Characterisation and Antimicrobial Studies. Bioinorganic Chemistry and Applications. 2014. DOI: http://dx.doi.org/10.1155/2014/276598

[23]            H.A. Bayoumi, Abdel-Nasser M.A. Alaghaz and Mutlak sh. Aljahdali. Cu (II), Ni (II), Co (II) and Cr (III) complexes with N₂O₂-chelating Schiff’s base ligand incorporating azo and sulfonamide moieties: spectroscopic, electrochemical behavior and thermal decomposition studies. Int. J. Electrochem. Sci. 8; 2013:9399–9413.

[24]            M.S. Lourenco, M.N DeSouza, A.C Pinheiro, M.L. Ferreira, R.B. Goncalves, T.M. Nogneira and M.A Peralta. Evaluation of anti-Tubercular activity of nicotinic and isoniazid analogues. ARKIVOC. 15; 2007:181-191.

[25]            N. Raman. Antibacterial study of the mannich base, N-(1-morpholino-benzyl) semicarbazide and its transition metal (II) complexes. Research Journal of Chemistry and Environment. 4; 2005:9.

[26]            U. Galm, S. Heller, S. Shapiro, M. Page, S.M. Li, and L. Heide. Antimicrobial and DNA gyrase-inhibitory activities of novel clorobiocin derivatives produced by mutasynthesis, Antimicrobial Agents and Chemotherapy. 48; 2004:1307– 1312.

[27]            E.J. Alvarez, V.H. Vartanian, and J.S. Brodbelt. Metal complexation reactions of quinolone antibiotics in a quadrupole ion trap. Analytical Chemistry. 69; 1997:1147–1155.

[28]            Mustapha Mandewale, Bapu Thorat, Y. Nivid, Ram Jadhav, Aarti Nagarsekar, Ramesh Yamgar. Synthesis, structural studies and antituberculosis evaluation of new hydrazone derivatives of quinoline and their Zn (II) complexes, Journal of Saudi Chemical Society, 2016. doi: http://dx.doi.org/10.1016/j.jscs.2016.04

[29]            Mustapha Mandewale, Santosh Kokate, Bapu Thorat, Sudhir Sawant, Ramesh Yamgar. Zinc complexes of hydrazone derivatives bearing 3,4-dihydroquinolin-2(1H)-one nucleus as new anti-tubercular agents, Arabian Journal of Chemistry, 2016. doi: 10.1016/j.arabjc.2016.07.016

 

 

 

 

Received on 08.08.2016         Modified on 18.08.2016

Accepted on 18.09.2016         © AJRC All right reserved