DNA-binding, cleavage, antibacterial and in vitro anticancer activity of copper(II) mixed ligand complexes of 2-(((6-chloro-1H-benzo[d]imidazol-2-yl)methyl)amino)aceticacid and polypyridyl ligands

Abstract A tridentate ligand(A), 2-(((6-chloro-1H-benzo[d]imidazol-2-yl)methyl)amino) aceticacid (Cl-BIGH) was synthesised by the Phillips condensation of 4-chlorobenzene-1,2-diamine and iminodiaceticacid in 1:2 molar ratio. Its Cu(II) mixed ligand complexes[Cu(II)-A-L] were obtained by involving other co-ligands(L): 2,2΄-bipyridine(L1), 4,4΄-dimethyl-2,2΄-bipyridyl(L2), 5,5΄-dimethyl-2,2΄-bipyridyl(L3) and 1,10 phenanthroline(L4). The complexes were characterized by elemental analysis, thermal analysis, molar conductance, magnetic moment measurements, X-ray diffraction, FTIR, UV–Visible, ESR spectroscopy, mass spectrometry and cyclic voltammetry. From the spectral and analytical data, the ternary complexes [Cu(Cl-BIGH)(L1-4)]ClO4 were found to form in 1:1:1(Cu(II): Cl-BIGH: L) molar ratio. The geometry of the mixed-ligand complexes were found to be 5-coordinated square pyramidal or trigonal bipyramidal with polycrystalline natures. The DNA binding and cleaving abilities, antibacterial and the in vitro cytotoxicity of the complexes were explored. The molecular docking was used to predict the efficiency of binding of the metal complexes with COX- 2. Communicated by Ramaswamy H. Sarma


Introduction
Transition metal complexes play an important role in nucleic acid chemistry due to their applications as sequence specific binding, therapeutic agents, structural probes (Franz & Metzler-Nolte, 2019;Guo & Sadler, 1999;Raja et al., 2012;Wu et al., 2009;Zheng & Tan, 2020). Metal complexes of the nitrogen-containing heterocyclic compounds such as benzimidazole and imidazole (Abonia et al., 2011) form an essential class of pharmacophores. Benzimidazole derivatives like astemizole, mebendazole, enviroxime and carbendazime have been widely used and commercialised (Kumaravel & Raman, 2017;Neochoritis et al., 2011). Benzimidazole ring shape is crucial for nucleotide synthesis as it serves as the nucleus of nitrogen bases (Abonia et al., 2011). Benzimidazole and its derivatives readily interact with biopolymers and appear to be promising systems for the synthesis of pharmocologicaly active molecules with structural similarities to vitamin-B12 derivatives (Paul et al., 2015). Benzimidazole and its derivatives have a fascinating biological action against a wide range of bacteria, fungi and viruses (Vicini et al., 2006;Weijie et al., 2015;Zhang et al., 2016). Transition metal complexes of benzimidazole-based ligands have been used in DNA binding and cleavage (Mansour & Ragab, 2019;Xiao-Tong et al., 2015), which are also renowned topoisomerase inhibitors (Singh & Tandon, 2011) with antitumor (Hranjec et al., 2008) and anticancer properties (Heba & Hanan, 2020).
The co ligands can control the stability and biological activity of corresponding metal complexes. Among various types of ligands, electron rich and functionalized pyridine ligands such as bipyridine, 4,4΄ -dimethyl-2,2΄ -bipyridyl, 5,5΄ -dimethyl-2,2΄-bipyridyl and 1,10 phenanthroline are promising class of ligands in coordination chemistry. Their hydrophobic and planar structures help the nitrogen atoms to bind the metal ions cooperatively (Austin et al., 2021;Cheng-Zhi et al., 2013).Therefore, the fusion of benzimidazole and pyridyl ligands in metal complexes expected to have extended biological activity. Cu(II) complexes of mixedligands are of great interest as they exhibit numerous biological activities. Copper is a bioimpact element with two biologically accessible oxidation states and its mixed-ligand complexes have been synthesized since they bring about oxidative cleavage of DNA.
A well-known metallo-drug, cisplatin used for treatment of cancer is also associated with some side effects (Oun et al., 2018). Therefore, several studies have been carried out to find better and cheaper therapeutic agents such as metal complexes of copper, nickel, cobalt, zinc, iron and ruthenium ions, which can show lesser side effects (Hussain et al., 2019;Kalaivani et al., 2014). Consequently, much attention has been paid to the non-platinum-based metal-ion complexes, which can interact with DNA. Coordination chemistry of Cu(II) complexes of benzimidazole-based ligands with NNO and NSO donor sites are interesting due to their structural and redox properties. Some Cu(II) complexes with amino acid-based ligands were also found to exhibit strong interaction with DNA and induced apoptosis in cancer cells, beside very few side effects (Alagesan et al., 2013;Azuara et al., 2010;Li et al., 2021;Santini et al., 2014).

Cell lines used for in vitro studies
The cell lines used for testing in vitro anticancer activity are HeLa-Human cervical carcinoma cell line, MCF-7 -Human breast carcinoma cell line, A549-Human lung cancer cell line, HEK 293 -Human embryonic kidney cells-Normal cell line. They were obtained with job number 1610 from NCCS, Pune, India.
Instrumentation IR spectra were recorded on a JASCO FTIR 5300 spectrometer. Elemental analysis for C, H and N was done using a FLASH Ea 1112 SERIES CHNS analyzer. EPR spectra were obtained using The HRMS data was obtained using JEOL GCMATE II GC-MS. The NMR spectra were recorded on Bruker Avance 400 MHz spectrometer.
Cyclic voltammetry (CV) was carried out with a Gamry-600 electrochemical analyzer having an electrochemical cell with a three-electrode system. The Ag |AgCl |KCl sat was used as reference electrode and glassy carbon as working electrode and platinum wire as an auxiliary electrode, while 0.1 M KCl was used as supporting electrolyte. Cyclic voltammetric titrations were performed at constant concentration (1 mM) and volume(10 mL) of the complex with varying concentration of DNA (0-40 mM).

Infrared spectral studies
In the IR spectrum of Cl-BIGH, strong bands at 3413, 2756 and 1572 cm À1 can be ascribed to the stretching vibrations of m(O-H), m(N-H) of aliphatic amine and m(C¼N) (azomethine) in imidazole ring respectively, which are the possible binding sites in the ligand. These frequencies are shifted or vanished in the IR spectrum of complexes, 1-4 as listed in Table 2, which suggest that the two nitrogens and one oxygen of the ligand are coordinated to the metal ion. A comparison of the IR spectrum of the ligand (Cl-BIGH(A)) and pyridyl co-ligands(L) with their Cu(II)AL complexes, 1-4 show considerable shift in the m(C¼N) stretching frequencies, indicate the formation of the ternary complexes and the Cl-BIGH act as monobasic tridentate and pyridyl ligands as bidentate ligands. As a result of coordination, the m(C¼N) stretching frequencies of the benzimidazole ring and pyridyl ligands shows a down field shift as compared to their free ligand (Cl-BIGH), suggesting coordination through the benzimidazole and pyridyl nitrogens of co-ligands (Virupaxappa et al., 1994). IR spectra of complexes, 1-4 are shown in Figures S10-S13 (Supporting Information). Generally, the IR spectrum of the free ligand(Cl-BIGH) showed a broad band around 3400-3500 cm À1 , which can be attributed to N-H and O-H stretching vibration of Cl-BIGH. The C-H deformation band around 880 cm À1 moved to lower frequency in the complexes. In all the complexes, bands around 624-612 cm À1 and 440-480cm À1 have been assigned to Cu-O and Cu-N bands, respectively.
The new strong broad asymmetric stretching and a sharp asymmetric bending bands at 1114-1089 and 625-628 cm À1 , in the IR spectra confirms the presence of tetrahedral ionic perchlorate anions in the complexes (Sharma et al., 1994;Shivakumaraiah et al., 2004;Yamanaka et al., 1999). These bands are absent in the spectrum of the free ligand. The absence of a broad intense band at 3500-2900 cm À1 region indicate the absence of water molecule in the complex (Allan et al., 1990). Thus, both the nitrogens of the pyridyl ligands(L) and two nitrogen and one oxygen atoms of the Cl-BIGH(A) are coordinated to the metal ion.

Electronic spectra and magnetic moment studies
The electronic absorption spectra of the Cu(II) complexes, 1-4 at 50 mM concentration were recorded at room temperature in methanol and are presented in Figure S14 (Supporting Information). The absorption spectrum of Cl-BIGH exhibited absorption band at 205 nm which are assigned to p!p Ã transition (Iftikhar et al., 1982).
A comparison of absorption spectra of the metal complexes with that of the free ligand indicates that the p!p Ã transitions are slightly perturbed by the chelation of ligand with metal ion. Ligand coordination is supported by the appearance of a strong band at 300-320 nm, corresponding to the ligand to metal charge transfer (LMCT) transition (Hathaway & Billing, 1970). p ! p Ã and intra-ligand charge transfer transition bands of the free ligand are shifted to the higher energy region in the spectrum of the complex and appear at 215 and between 235-245 nm, respectively. Similarly, the band at 282 nm of Cl-BIGH is assigned to n!p Ã transition of C ¼ O, which was observed in all the complexes, confirms the formation of the complex (Fadini & Schnepel, 1989).
The electronic spectrum of the copper complexes displays a lower energy band between 660 and 671 nm, which corresponds to the transition from the B 1 (d x2Ày2 ) ground state to the excited A 1 (d z2 ), B 2 (d xy ) and E(d xz , d yz ) states.
In addition all the complexes show magnetic moments (Table 3) in the range of 1.80-1.85 B.M., characteristic of the 5-coordinated square pyramidal or trigonal bipyramidal Cu(II) complexes (Kadhiravansivasamy et al., 2017).

EPR spectral study
The EPR spectra of the complexes, 1-4 recorded at room temperature are presented in Figure S15 (Supporting Information) and their g values are listed in the Table 3. All the complexes are isotropic with g iso ¼ 2.130, 2.116, 2.127 and 2.133 for the complexes 1, 2, 3 and 4 respectively. The absence of hyperfine structure indicates that the interactions are dipolar in nature (Patel et al., 2000).

X-ray powder diffraction studies
The X-ray powder diffractograms were recorded on a SMART Bruker D8 advance X-ray diffractometer. The sharp lines in powder XRD indicate that the complexes are highly crystalline in nature. The X-ray diffractogram of complexes, 1-4 are presented in Figure S16 (Supporting Information). The average crystallite size of the complexes was calculated using Scherrer's formula . The complexes, 1-4 have an average crystallite size of 62, 71, 60 and 59 nm, respectively. Thermogravimetric analysis of the complexes Thermal behavior of the complexes, 1-4 are studied by thermogravimetric analysis (TGA) and differential thermal analysis (DTA) at 25 À 1000 C and the thermogram are presented in Figure S17 (Supporting Information), while the results are listed in Table 4. The thermogram of 1 show that it is thermally stable in the range of 20-260 C. Decomposition of the complex begins at 260 C and completes at 263 C. The DTA also shows an exothermic peak at 262.9 C, corresponding to the decomposition of the complex, 1. Similarly, the complex 2 decomposes within temperature range 272-276 C and the corresponding exothermic peak can be observed at 274.3 C.
Complexs 3 and 4 shows two sharp and one gradual decomposition stages in thermogram ( Figure S17) between 200 and 400 C. In the first two stages, perchlorate ion and Cl-BIGH ligand decompose exothermically at 226.2 C and 310.1 C, respectively, for complex 3 and at 246.2 C and 350 C for complex 4. All the complexes decompose to copper oxide as a final residue. The endothermic peaks in DTA indicates corresponding chemical changes. The DTA shows two distinct exothermic peaks and TG shows continuous decomposition which do not facilitate calculation of the mass loss at intermediate stages. The absence of weight loss below 100 C in all the complexes indicate the absence moisture and crystalline water molecules.

Electrochemical studies
The electrochemical properties of the complexes, 1-4 have been studied to monitor the structural changes accompanying electron transfer. The representative cyclic voltammograms of 1 mM solution of complex in methanol at 100 mVs À1 are presented in Figure S18 (Supporting Information). In the complexes, 1 and 2 no representative redox peak is observed. A broad and poorly defined oxidation and reduction waves are observed for 1 and 2.
The cyclic voltammogram of complex, 3 shows only one redox peak in the studied potential range at þ178.5 mV for the oxidation in the forward scan and at þ66.43 mV for the reduction peak in the reverse scan. The peak potential separation, DE p ¼ (Epa À Epc), between the anodic and cathodic peaks is 112 mV. For the complex, 4 the oxidation peak was observed at þ238 mV and reduction peak at À 46.85 mV with 284 mV peak separation.
The oxidation and reduction peak currents of complexes, 1-4 increases with the increase in scan rate as shown in the Figure S19 (Supporting Information). The study indicate that the anodic peak potentials shift to more negative values and the cathodic peak potential shift to more positive values. The increase in separation between the peak potential by increasing the scan rate is a characteristic behavior of a quasi-reversible system. Repeated scans with different scan rates show that the dissociation does not take place in the complexes.
The effect of scan rate on the peak potential for the complexes, 1-4 were also investigated by increasing the scan rate. Repeated scans with different scan rates ( Figure S19) show that dissociation does not take place in the complexes. The anodic peak potentials shift to more negative values and the cathodic peak potentials shift to more positive values. The increase in separation between the peak potentials, E by increasing the scan rate is a characteristic behavior of a quasi-reversible system (Ibrahim et al., 2012).

Proposed structures
Based on the spectral analysis, following structures as shown in Figure 1 have been proposed for the complexes, 1-4.

Biological activity
DNA binding and cleavage studies Electronic absorption spectra. The interaction between the complexes and CT-DNA was monitored by electronic absorption spectra (Baldini et al., 2004). The absorption spectra of the copper (II) ternary complexes, 1-4 in the absence and in the presence of CT-DNA are shown in Figure 2. Addition of increasing amounts of CT-DNA to the complexes results in the moderate hypochromism. This indicates the interaction between DNA and the complexes to be intercalative (Tysoe et al., 1993).
The concentration of CT DNA in phosphate buffer (pH ¼ 7.2) was determined from UV absorbance at 260 nm (e ¼ 6600 M À1 cm À1 ). The absorbance ratio at 260 nm and 280 nm is between 1.8 and 1.9, indicating that the DNA is protein free (Reichmann et al., 1954). The stock solutions were kept at 4 C, buffer and other solutions were prepared by redistilled water free from CO 2 . The absorption spectra of the complexes in aqueous medium were measured in the absence and presence of CT-DNA. The titrations were carried out with varied DNA concentrations (0-100 mM) and a constant complex concentration. DNA binding titrations were  Absorption spectra were recorded in each successive addition of CT-DNA to the complex. Each DNA complex and solution was incubated for 10 min at 25 C, after which the absorbance readings were recorded. Then the data was fitted to Equation (1) (Gonzalez-Perez et al., 2002).
Metal complexes can bind to the DNA in different binding modes based on their ligand structure and charge. As DNA double helix possesses many hydrogen bonding sites, accessible to both the minor and major grooves, it is likely that the carboxylate and amino groups of Cl-BIGH in the complexes form hydrogen bonds with DNA, which may contribute to the hypochromism as observed in the absorption spectra. The extent of hypochromism is indicative of the strength of the intercalatative binding (Chao et al., 2002). To compare the DNA-binding affinities of the complexes 1-4 quantitatively, their intrinsic binding constants(K b ) with DNA were calculated by monitoring the changes in absorption spectra with increasing concentration of DNA(0-40 lM) at fixed complex concentration (50 mM) using the Equation (1) and were found to be 0.71 Â 10 5 M À1 (1) , 0.26 Â 10 4 M À1 (2), 0.16 Â 10 6 M À1 (3) and 4.34 Â 10 6 M À1 (4), respectively.
These values are lower than the classical intercalator (EtBr), whose intrinsic binding constant is in the range of 10 6 -10 7 M À1 (Waring, 1965). The binding constants of the complexes, 0.71 Â 10 5 M À1 (1), 0.26 Â 10 4 M À1 (2), 0.16 Â 10 6 M À1 (3) and 4.34 Â 10 6 M À1 (4) indicate that, the 4 is having high binding affinity towards DNA, may be due to the presence of extended planar aromatic ring in phenanthroline (Schmid et al., 2018).  Owing to the resemblance between electrochemical and biological reactions, the redox mechanisms taking place in the body and at an electrode follow similar principles. It can be assumed that the peak potential and current intensity of the complex changes with the nucleic acid interactions (Afzal et al., 2013). The changes in peak height (Ip) of the complex on addition of CT-DNA can be used for the determination of the binding constant of the complex with DNA, whereas, the shift in peak potential can be used for ascertaining the mode of interaction. The decrease in peak current of complexes, 1-4 by the addition of varying concentration of DNA(0-40 mM) was used to calculate the binding constant by following Equation (2) (Suzen & Buyukbingol, 2000).
where K is the binding constant, A is proportionality constant and I 0 and I are the peak currents of the complex in the absence and presence of DNA, respectively. The binding constants were calculated from the intercept of the plot of 1/ [DNA] vs. 1/(1-I/I 0 ). The cyclic voltammetric behavior of complexes, 1-4 in phosphate buffer (pH % 7.2) in the absence and presence of DNA at varying concentrations is shown in Figure 3. The complexes 1-4 show increase in peak current with cathodically shifted peak potential in the presence of DNA, due to the intercalating binding mode between complexes and DNA (Ni et al., 2006). (2), 0.258 Â 10 3 M À1 (3) and 0.97 Â 10 3 M À1 (4) were obtained as shown in Figure 4. The complex, 1 and 4 showed higher binding affinity with DNA compared to other complexes.
Viscosity measurements. The hydrodynamic measurement is considered as a precise and critical test to study the binding mode of DNA with metal complexes . The viscosity is sensitive to the changes in the length of DNA and the sensitivity of this method mainly depends on the changes in the length of DNA, which occur as a result of its different binding modes with the guest molecules. A classical intercalation mode causes a significant increase in the viscosity of DNA due to lengthening of base pairs at intercalation sites results in an increase in overall DNA length. To understand the interaction modes, viscosity measurements were carried out for the complexes, 1-4 at variable concentrations (0.4, 0.8, 1.2, 1.6, 2.0 lM), which was introduced into the DNA solution (0.02 mM). The plots of relative viscosity (g/g 0 ) 1/3 versus [complex]/DNA] ratio show a significant increase in the relative viscosity (Zhang et al., 2001) of DNA with increasing concentration of complexes 1-4, as shown in the Figure 5. The result of the study further suggests an  intercalative binding mode for the complexes, with the DNA. Thus, the viscosity measurements supports the results of electronic absorption titrations and cyclic voltammetric titrations. Therefore, the interaction between the complexes and DNA is through intercalative mode (Rodger et al., 2001).

DNA cleavage
The cleavage of the super coiled pUC19 plasmid DNA was studied by gel electrophoresis on agarose. Migration of DNA in gel electrophoresis occurs under the influence of electric potential. Under electric field the DNA act as negatively charged species and migrate towards anode and such migration depends on the DNA size, buffer, electric field and the density of the gel. The DNA cleavage depends upon the ability of conversion of amount of super coiled DNA (Form I) to nicked circular form (Form II) as shown in the Figure 6. The DNA cleavage ability of the complexes, 1-4 were studied at the complex concentration in the range of 10-120 mM and DNA concentration 300 ng/lL. These samples of 5 mL in TAEbuffer were incubated at 37 C for 30 min. At a higher concentration of complex, 4 (20 lM), super coiled DNA was fully converted to nicked form as shown in the Figure 6. Complexes 2 and 3 converted super coiled form to nicked form to some extent, however, it could not covert completely even at a higher concentration of 120 mM. The complex 1 did not show any DNA cleavage ability. The observed cleavage efficiency of complexes follows the order, 4 > 3-2 > 1, depending upon the co-pyridyl ligand. The effect of the DNA cleavage by 4 was observed at lower concentration (20 mM), since it showed better DNA interaction among all the complexes. The efficient nuclease activity of 4 is based on the enhanced formation and stabilization of Cu(II) by the presence of 1,10-phenanthroline which is also hydrophobic nature. Thus the complex 4 exhibit better nuclease activity than other complexes due to the an extensive interaction of the aromatic rings of 1,10-phenanthroline (Ramakrishnan et al., 2011).

Antimicrobial activity
The in vitro antimicrobial activity of the complexes, 1-4 was tested against gram positive bacteria, Bacillus subtilis and Staphylococcus aureus and gram negative bacteria, Escherichia coli and Pseudomonas aeruginosa by well diffusion method, using nutrient agar medium and it was inoculated with microorganisms. The well was filled with 20 lL of the test solution (1 mg/mL) and the plate was incubated for 24 h at 37 C. All the complexes showed moderate activity against G(þ) Bacillus subtilis and Staphylococcus aureus and inactive against other species. The complex, 4 show high activity among all the complexes ( Figure S20, Supporting Information) Table 5. This is due to the extended conjugation in the complex. The activity follows the order: 4 > 3 > 2 > 1.

Molecular docking studies with COX-2
In modern drug discovery, protein-ligand or protein-protein coupling plays an important role in predicting the orientation of the ligand when it binds to a protein or enzyme receptor, using shape and electrostatic interactions to quantify them. In addition to hydrogen bonds and Coulombic interactions, van der Waals interactions also play an important role. The sum of all these interactions is estimated by the coupling score, which represents the possibility of binding. The coupling plays a crucial role in rational drug design. COX1 and COX2 are two different isoforms of cyclooxygenase and play a crucial role in the conversion of arachidonic acid to prostaglandins (Lipsky et al., 1998). Prostaglandins (PG) are involved in various pathophysiological processes such as carcinogenesis, inflammatory reactions and cardiovascular problems. COX2 is undetectable in normal tissues, but is induced by pro-inflammatory cytokines, carcinogens and growth factors, implying a role for COX2 in the control of cell growth and inflammation (Subbaramaiah et al., 1996). In inflammatory tissues such as rheumatoid synovium, the COX2 expression is upregulated and produces prostaglandin precursors that are eventually converted to prostaglandins (Prasit et al., 1999). Recent studies on selective COX2 inhibition showed suppression of colon cancer and inflammation induced by azoxymethane. This demonstrated the importance of COX2 as a target for cancer therapy and anti-inflammatory activity (Amaravani et al., 2012;Subhashini et al., 2004). Consequently, suppression of COX2 levels will be an effective strategy for carcinogenesis and inhibition of inflammation.
In order to investigate the binding mode of the target complexes, 1-4 with COX-2, docking studies were performed (Figure 7). The optimized ligands (i.e., complexes, 1-4) were docked back into the binding site of the enzyme (COX-2) and superposed with the native ligand. The result of the docking studies is presented in Table 6. The most important interactions observed for the complexes, 1-4 with COX-2 are hydrogen bonding interactions. In this study, it was found that LEU23, ASP25, ILE84, ASN144, ARG87of COX-2 are important for strong hydrogen bonding interaction with the complexes, 1-4. All the complexes, 1-4 showed best docking result with COX-2.

In vitro anticancer activity
The cytotoxicity assay was performed using MTT reagent (Alet van et al., 2015). In this colorimetric assay, MTT (3-[4, 5-dimethylthiazol-2-yl]-2, 5-diphenyltetrazolium bromide), a water soluble yellow colored tetrazolium salt, was converted in to an insoluble purple formazan by cleavage of the tetrazolium ring by succinate dehydrogenase present within the mitochondria. As the formazan product being impermeable to the cell membranes, it accumulates in healthy cells. Since reduction of MTT could only occur in metabolically active cells, the intensity of purple colour was used as a measure of the viability of the cells. The intensity was measured by spectrophotometer after dissolving formazan crystal in DMSO.
The cytotoxicity assay for the complexes, 1-4 were assessed using the method of MTT reduction. The Doxorubicin was used as a control. All the complexes were found to be cytotoxic to human cervical cancer cells (HeLa), human breast cancer cells (MCF-7) and human lung cancer cells (A549). The IC 50 values for complexes are listed in the

Conclusion
The Copper(II) mixed ligand complexes, 1-4 have been successfully synthesized from Cl-BIGH and poly pyridyl co-ligands(L): 2,2΄ -bipyridine(L 1 ), 4,4΄ -dimethyl-2,2΄ -bipyridyl(L 2 ), 5,5΄ -dimethyl-2,2΄ -bipyridyl(L 3 ) and 1,10 phenanthroline(L 4 ) and characterized by various spectro analytical techniques. The complexes are of square pyramidal/trigonal bipyrimadal coordination geometry. EPR study of the complexes showed a broad spectrum without any hyperfine splitting indicating dipolar nature of the bonding. The DNA binding affinity of the complexes was investigated by spectrophotometric, cyclic voltammetric and viscosity measurements. The results indicated that the complex interacts with calf thymus DNA through an intercalation mode. The nuclease activity of the metal complexes, indicate that the complex 4 can effectively cleave the pUC19 DNA at 20 mM concentration. The antibacterial studies show that all the complexes exhibit good activity against Bacillus subtilis and Staphylococcus aureus. From the docking studies, the complexes are known to be potent COX-2 inhibitors. The cytotoxicity of complexes against different cancer cell lines (HeLa, MCF-7, A549) and healthy cell line (HEK 293) was investigated where in the complexes 1, 2 and 4 exhibit good cytotoxicity. Thus, the molecular docking study revealed a direct correlation between the docking affinity score and the biological activity.