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Two sets of mononuclear N, O-chelate complexes, 1a [Co(L1)2(H2O)2], 1b [Ni(L1)2] and 1c [Cu(L1)2], and 2a [Co(L2)2(H2O)2], 2b [Ni(L2)2] and 2c [Cu(L2)2], from respective Schiff base ligands, HL1: 2-((E)-(6-(trifluoromethoxy)phenylimino)methyl)-5-methylphenol, C15H12F3NO2) and HL2: 2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4,6-dichlorophenol, C14H8Cl2F3NO2) have been synthesized and well-characterized by analytical and various spectroscopic techniques like mass spectrometry, FT-IR, UV-visible, magnetic susceptibility, ESR and thermogravimetric studies. The geometries are proposed as octahedral for complexes 1a and 2a, whereas square planar for complexes 1b, 1c, and 2b, 2c. DNA binding study was investigated against calf thymus DNA for synthesized complexes comparing with parent ligands and resulted in intercalation mode of binding which was further supported by fluorescence quenching and viscometric titrations. Nuclease efficacy was also investigated against supercoiled pBR322 DNA and a good cleavage pattern was shown by metal complexes. The complexes were found to possess good antimicrobial activity compared to free ligands against bacterial species, Bacillus amyloliquefaciens and Escherichia coli as well as fungal species, Macrophomina phaseolina and Sclerotium rolfsii.

Three mononuclear binary metal complexes of the general formula [M(L)2] and [M1(L)3] (M = Cu, Ni and M1 = Co, LH = 2-(((furan-2-yl)methylimino)methyl)-4-methylphenol) were synthesized. The obtained compounds could be crystallized and were successfully characterized using spectroscopic techniques, together with elemental analysis. The spectroscopic elucidation indicates a monobasic bidentate nature of the ligand, coordinated via a deprotonated phenolic oxygen atom and an azomethine nitrogen atom, which suggests a square planar geometry around the copper and nickel ions, and an octahedral geometry around the cobalt ion. The absorption spectral titrations of the complexes with DNA impart that the binding affinity (Kb) of the complexes vary in the order 3 > 1 > 2, with hypochromism percentages of 12.44–10.47. The interactions of the complexes with pBR322 DNA were followed by electrophoretic mobility spectroscopic studies and the results distinctly show that the complexes exhibit good cleavage properties. The antioxidant activities of the synthesized compounds were investigated with DPPH and the complexes have superior radical scavenging activity. The cytotoxic activities of all the compounds were evaluated towards the human breast adenocarcinoma cell line (MCF-7) and the oral carcinoma cell line (KB3) using an MTT assay with Etoposide as a standard and the results show the IC50 values of the complexes vary from 40.29 ± 0.87 to 75.07 ± 0.83. The complexes and the ligand were screened for their in vitro antibacterial activity against bacterial strains; the complexes are more active than the ligand against the tested microbial strains.

Metal complexes of the type [M(L)2] 1–3, (M = Co(II), Ni(II) and Cu(II)) of ligand (LH = 2-benzo[d]thiazol-6-ylimino)methyl)benzene-1,4-diol, have been synthesized and characterized by elemental analysis, NMR, Infrared, UV–Visible, ESI-Mass, magnetic moments and ESR spectroscopic methods. Based on spectral data a square planar geometry has been proposed for all the complexes. The interaction of metal complexes with CT-DNA was investigated using UV–Vis absorption and fluorescence spectroscopy. The absorption and fluorescence spectral studies indicate a non-covalent interaction between the metal complexes and DNA base pairs. The competitive studies revealed that the complexes could interact the DNA through an intercalative mode and induce oxidative and photolytic DNA cleavage mediated by reactive oxygen species (ROS), and it is found that the Cu(II) complex cleaved DNA more effectively compared to Co(II) and Ni(II) complexes. In addition, antimicrobial activity of all the complexes was also examined.

Three novel Cu(II) complexes 1 [Cu(L1)2], 2 [Cu(L2)2] and 3 [Cu(L3)2], where L1H = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-6-tert-butylphenol, L2H = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4,6-di-tert-butylphenol and L3H = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-4,6-dibromophenol were synthesized and characterized by elemental analysis, FT-IR, UV–Visible, 1H NMR, 13C NMR, ESI mass, EPR and magnetic susceptibility studies. Based on spectroscopic and analytical data, a square planar geometry is assigned for all complexes. DNA binding and cleavage studies against calf thymus DNA (CT-DNA) and supercoiled pBR322 DNA respectively revealed an intercalative mode of binding and also cleave pBR322 DNA in an efficient manner. The ligands and their complexes were examined for antimicrobial activity against bacterial species E. coli, B. subtilis and fungal species S. rolfsii and M. phaseolina and found that all the Cu(II) complexes show more activity than the free Schiff base ligands. The antioxidant activity of metal complexes have also been determined using DPPH assay and found that the complexes are found to be good free radical scavengers.

Three novel binary metal complexes; 1 [Cu(L)2], 2 [Ni(L)2] and 3 [Co(L)3] where, L (2-(((furan-2-yl) methylimino)methyl)-6-ethoxyphenol, C14H15NO3), were synthesized and characterized by various spectral techniques. Based on spectral studies square planar geometry is assigned for Cu(II) and Ni(II) complexes, whereas Co(III) owned octahedral geometry. Ligand, [Cu(L)2] and [Ni(L)2] are crystallized and found to be monoclinic crystal systems. CT-DNA absorption binding studies revealed that the complexes show good binding propensity (Kb = 5.02 × 103 M−1, 2.77 × 103 M−1, 1.63 × 104 M−1 for 1, 2 and 3 respectively). The role of these complexes in the oxidative and photolytic cleavage of supercoiled pBR322 DNA was studied and found that the complexes cleave the pBR322 DNA effectively. The catalytic ability of 1, 2 and 3 follows the order: 3 > 1 > 2. Antioxidant studies of the new complexes revealed that they exhibit significant antioxidant activity against DPPH radical. The Schiff base and its metal complexes have been screened for antibacterial studies by Minimum Inhibitory Concentration method. It is observed that all metal complexes showed more activity than free ligand.

In this study, new three Schiff base ligands and their Cu(II) complexes: 1 [Cu(L1)2], 2 [Cu(L2)2] and 3 [Cu(L3)2], where HL1-HL3 represent Schiff base ligands (HL1 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-6‑chloro-4-fluorophenol, HL2 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-3,5-dimethoxy-phenol and HL3 = 2-(4-(trifluoromethoxy)phenylimino)methyl)-5-(diethylamino)phenol) were synthesized. The structural features were confirmed from their micro analytical, Fourier transform infrared (FT-IR), nuclear magnetic resonance (NMR), UV–visible, mass, magnetic susceptibility measurements, ESR and thermal analysis. The spectroscopic approaches proposed a square planar geometry for all Cu(II) complexes. The stability of the binary metal(II) complexes has been calculated from quantum chemical parameters using highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energies. All the tested complexes preferably bind to CT-DNA via intercalation mode as resulted from UV spectroscopy and EB competition assay studies. In addition, the metal complexes exhibited good cleavage ability against the pBR322 DNA in the presence and absence of H2O2 as well as UV light. The antioxidant activity of 1–3 was evaluated by 1,1-diphenyl-2-picryl-hydrazyl (DPPH) stable free radical with reference of ascorbic acid. Of these, complex 1 show good antioxidant activity. The in vitro cytotoxicity studies of the ligands and their complexes against human lung (A549) and breast (MCF7) cancer cell lines showed significant activity. The Schiff base ligands and their metal complexes were screened for their biological activities and are found to be the complexes have higher activities than the free Schiff bases.

Two mononuclear metal complexes, [Cu(L1)2] (1) and [Cu(L2)2] (2) of the respective Schiff bases, HL1 = 2-((E)-(6-(trifluoromethoxy)benzo[d]thiazol-2-ylimino)methyl)-4-methoxyphenol and HL2 = 2-((E)-(6-(trifluoromethoxy)benzo[d]thiazol-2-ylimino)methyl)-4,6-dibromophenol were synthesized and well characterized by analytical and various spectroscopic techniques like elemental analysis, NMR, mass spectrometry, IR, UV, ESR and thermogravimetric analyses. These spectral studies gave a square planar geometry for both the complexes. These complexes underwent DNA investigation against calf thymus DNA and supercoiled pBR322 DNA. The complexes bound the DNA through an intercalation mode and the binding affinity order follows as 1 > 2 > HL2 > HL1. Both complexes show good cleavage ability against double-stranded pBR322 DNA under oxidative and photolytic conditions. In vitro antimicrobial study resulted in both complexes have shown marked biocidal potential compared to respective free ligands.

Two new series of binary metal complexes [M(L 1 ) 2 ] and [M(L 2 ) 2 ] where, M = Cu(II), Ni(II) & Co(II) and L 1 = 4-((3,4-dimethylisoxazol-5-ylimino)methyl)benzene-1,3-diol; L 2 = 2-((3,4-dimethylisoxazol-5-ylimino)methyl)-5-methoxyphenol were synthesized and characterized by elemental analysis, 1 H NMR, 13 C NMR, FT-IR, ESI mass, UV–Visible, magnetic moment, ESR, SEM and powder XRD studies. Based on these results, a square planar geometry is assigned for all the metal complexes where the Schiff base acts as uninegatively charged bidentate chelating agent via the hydroxyl oxygen and azomethine nitrogen atoms. DNA binding studies of all the complexes with calf thymus DNA have been comprehensively investigated using electronic absorption spectroscopy, fluorescence quenching and viscosity studies. The oxidative and photo cleavage affinity of metal complexes towards supercoiled pBR322 DNA has been ascertained by agarose gel electrophoresis assay. From the results, it is observed that all the metal complexes bind effectively to CT-DNA via an intercalative mode of binding and also cleave pBR322 DNA in a promising manner. Further the Cu(II) complexes have shown better binding and cleavage properties towards DNA. The antimicrobial activities of the Schiff bases and their metal complexes were studied on bacterial and fungal strains and the results denoted that the complexes are more potent than their Schiff base ligands.

Two novel Schiff bases, L1 = (2-benzo[d]thiazol-6-ylimino)methyl)-4,6-dichlorophenol), L2 = (1-benzo[d]thiazol-6-ylimino)methyl)-6-bromo-4-chlorophenol) and their bivalent transition metal complexes [M(L1)2] and [M(L2)2], where M = Cu(II), Co(II) and Ni(II) were synthesized and characterized by elemental analysis, NMR, IR, UV–visible, mass, magnetic moments, ESR, TGA, SEM, EDX and powder XRD. Based on the experimental data a square planar geometry around the metal ion is assigned to all the complexes (1a-2c). The interaction of synthesized metal complexes with calf thymus DNA was explored using UV–visible absorption spectra, fluorescence and viscosity measurements. The experimental evidence indicated that all the metal complexes strongly bound to CT-DNA through an intercalation mode. DNA cleavage experiments of metal(II) complexes with supercoiled pBR322 DNA have also been explored by gel electrophoresis in the presence of H2O2 as well as UV light, and it is found that the Cu(II) complexes cleaved DNA more effectively compared to Co(II), Ni(II) complexes. In addition, the ligands and their metal complexes were screened for antimicrobial activity and it is found that all the metal complexes were more potent than free ligands.

Binary complexes of Cu(II), Ni(II) and Co(II) were synthesized using two novel Schiff bases $$\mathbf{L}_{1}$$ = 2-(-(benzothiazol-6-ylimino)methyl)-4-chlorophenol (BTEMCP), $$\mathbf{L}_{2}$$ = 2-(-(benzothiazol-6-ylimino)methyl)-4-nitrophenol. The Schiff bases and metal complexes were characterized by analytical and spectral methods like elemental analysis, Mass, $$^{1}\hbox {H}$$ -NMR, $$^{13}\hbox {C}$$ -NMR, UV-Vis, IR, ESR, SEM, EDX, XRD and magnetic susceptibility measurements. From the analytical data, square planar geometry has been proposed for all the metal complexes. The binding interaction between the metal complexes and DNA was investigated by means of electronic absorption, fluorescence spectroscopy and viscosity measurements. The DNA cleavage ability of the metal complexes was also evaluated by agarose gel electrophoresis method. These studies revealed that the complexes showed an intercalative mode of binding to CT DNA and also effectively cleaved the supercoiled pBR DNA. The synthesised compounds were evaluated for in vitro antibacterial activity against Gram positive and Gram negative bacteria, and found that the metal complexes showed more potent biocidal activity than the Schiff bases. SYNOPSIS Six mononuclear metal complexes of benzothiazole Schiff bases were synthesized and characterized. The DNA interaction studies showed that all the complexes bind with CT-DNA through an intercalative mode. Supercoiled pBR322 DNA was effectively cleaved by the complexes . All the metal complexes exhibited better antibacterial activity than the Schiff bases from which they were prepared.

In the last few decades, the interaction between metal complexes and DNA has been the main subject of study for many researchers. DNA is the primary intracellular target for most anticancer therapi...

A series of bivalent metal complexes M(L1)2 and M(L2)2 where M = Cu(II), Ni(II), Co(II) and HL1=2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-chlorophenol, HL2=2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-nitrophenol were synthesized and characterized by elemental analysis, SEM, Mass, 1H NMR, 13C NMR, UV–Vis, FT-IR, ESR and magnetic susceptibility measurements. Based on the analytical and spectral data a square planar geometry has been assigned to all the metal complexes. DNA binding properties of these complexes have been explored using electronic absorption spectroscopy, fluorescence spectroscopy and viscosity measurements. The experimental evidence indicated that these binary complexes strongly bind to calf thymus DNA through an intercalation method. DNA cleavage efficacy of these metal(II) complexes have been investigated with super-coiled pBR322 DNA by gel electrophoresis in presence of H2O2 and UV light, and found that all complexes showed better nuclease activity. The in vitro antimicrobial activity results by paper disc method against few bacterial pathogens such as Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis and Staphylococcus aureus as well as fungal species Aspergillus niger and Candida albicans showed that the complexes are more biocidal than free ligands. Further, the compounds were screened for antioxidant activity using 1,1-diphenyl-2-picryl hydrazyl (DPPH) which was compared with a standard drug ascorbic acid.

Bidentate Schiff bases L1H and L2H were synthesized. Mono nuclear complexes [M(L1)2] and [M(L2)2] where, M = Cu(II)/Ni(II)/Co(II) were prepared and thoroughly characterized by various techniques. Square planar geometry has been envisaged for all the metal complexes, while the Schiff bases coordinated through the phenolic oxygen and azomethine nitrogen atoms. Interactions of complexes with CT-DNA and circular super coiled pBR322 DNA were delved by UV–Visible spectra, fluorescence, viscosity studies, as well as agarose gel electrophoresis method. The results displayed that the complexes interact moderately with CT-DNA via an intercalative mode and could also cleave DNA efficiently. The compounds were screened for their in-vitro antimicrobial activities against the selected microorganisms, data assert on the tested compounds as good bactericides and fungicides. Antioxidant activity by DPPH method emphasized that complexes can act as free radical scavengers.

Four mononuclear metal chelated complexes, [Co(L)] (1), [Ni(L)] (2), [Cu(L)] (3) and [Zn(L)] (4), were designed and synthesized from a novel quadridentate salen-type Schiff base ligand (H2L) derived from 2-hydroxy napthaldehyde and 4-fluoro-1,2-phenylenediamine. The chemical structures of synthesized compounds were fully characterized by various techniques. Spectral and analytical investigations clearly suggested that a square planar geometry around metal centre. The thermal analysis (TGA) of these complexes indicated greater thermal stability and various steps involved in thermal decomposition of metal complexes. The binding ability between the metal complexes and CT-DNA was investigated by UV-Vis, fluorescence spectroscopy and viscometric experiments which revealed an intercalation binding mode of binding. The cleavage property of metal complexes against pBR322 DNA has been explored. The antioxidant activity of M(II) complexes against active free radicals was determined by DPPH free radical scavenging experiment. Furthermore all compounds were screened against antimicrobial activity.

A series of six novel mononuclear Schiff base complexes 1 [Co(L1)2], 2 [Ni(L1)2], 3 [Co(L2)2], 4 [Ni(L2)2], 5 [Co(L3)2], and 6 [Ni(L3)2] have been synthesized and characterized by several physicochemical techniques. Co(II) and Ni(II) complexes possess a square planar coordination environment composed of N,O donor atoms. The results of these studies suggest that the metal complexes bind to DNA through intercalation. The mono nuclear complexes were found to cleave the pBR-322 DNA in the presence of oxidative and photolytic cleavage. The antibacterial activity of all the complexes was studied against four bacterial strains. Among them metal complexes have the moderate potential activity against microorganisms. Furthermore, the antioxidant activity of the metal complexes was determined by the DPPH radical scavenging method, the complex 5 was shown the good DPPH scavenging activity with IC50 value 07.45 ± 1.52 μM.

A series of six novel metal complexes of the type [M(L1)2] 1a-1c and [M(L2)2] 2a-2c, where, M = Cu(II), Ni(II), Co(II), HL1 = 2-(5-(trifluoromethyl)-2-methoxyphenylimino)methyl)-4,6-dichlorophenol and HL2 = 2-(5-(trifluoromethyl)-2-methoxyphenylimino)methyl)-4-bromo-6-methoxyphenol, have been synthesized and characterized by several physicochemical techniques. Having a base of spectroscopic and analytical data, complexes 1a, 1c, 2a and 2c showed a square planar geometry, whereas, complexes 1b and 2b owned a octahedral geometry around the metal ion. Thermal decomposition process of complexes 1a-2c is nonspontaneous, i.e., the complexes are thermally stable. DNA binding (UV–Visible absorption and fluorescence) studies against calf thymus DNA (CT-DNA), revealed an intercalative mode of binding. The complexes along with corresponding ligands have been investigated for their in-vitro cytotoxic activity against two human cancer cell lines such as HeLa and A549 using cisplatin as standard drug under MTT assay. All the complexes showed higher cytotoxicity than the parent ligand and moderate to cisplatin. In addition, antimicrobial activity of all the compounds was also examined.

Novel Schiff base (L) derived from 6-aminobenzothiazole and 4-methoxy salicylaldehyde and its bivalent Cu(II) (1), Ni(II) (2) and Co(II) (3) metal complexes were synthesized and thoroughly characterized by various analytical and spectral techniques. From the data a square planar geometry is assigned for all complexes. The DNA interaction studies of complexes with CT-DNA were carried out by UV–Vis absorption, fluorescence and viscosity measurements. These studies revealed that the complexes bind to CT-DNA by intercalative mode. DNA cleavage capacity of all the metal complexes was studied by agarose gel electrophoresis method. Further, the antibacterial studies of metal complexes were evaluated and it is observed that all complexes showed grater activity than free ligand. In addition, in-vitro cytotoxicity of these complexes on tumor cell lines HeLa, A549 and MCF-7 have been examined by MTT assay. The complexes showed greater cytotoxicity than the free Schiff base ligand.

A series of bivalent metal complexes [M(L1)2] and [M(L2)2] where M = Co(II), Ni(II), Cu(II) and newly synthesized Schiff bases L1 = (1-(5-(4-fluorophenyl)isoxazol-3-ylimino)methyl)napthalen-2-ol), L2 = (2-(5-(4-fluorophenyl)isoxazol-3-ylimino)methyl)-4-methylphenol) have been synthesized and characterized by elemental analysis, UV–Vis, FT-IR, Mass, NMR, ESR, magnetic moment, TGA, SEM and powder XRD analyses. Based on the spectral data, all the complexes adopted a square planar geometry around the metal ion. The interaction of metal complexes with CT–DNA was determined by using UV–absorption, fluorescence and viscosity measurements. And these results showed that the complexes moderately intercalate with CT–DNA. The DNA cleavage studies of metal complexes showed a significant cleavage of pBR322 DNA. The antioxidant activity of complexes was determined by DPPH• free radical scavenging assay. The antimicrobial activity of all the compounds was screened by disc diffusion method and it is found that the complexes showed better activity than the free ligands.

A series of six new metal complexes of the type [Cu/Co/Ni(L1)2] 1–3 and [Cu/Co/Ni(L2)2] 4–6, where, HL1 = (2-benzo[d]thiazol-6-ylimino)methyl)-4-methoxyphenol and HL2 = (2-benzo[d]thiazol-6-ylimino)methyl)-4-methylphenol, have been characterized by several physicochemical techniques. The metal complexes were subjected to study their DNA binding, cleavage, antioxidant and antimicrobial activity. These complexes are found to be strong binders to CT-DNA. The binding constants (Kb) estimated by the absorption spectral study and the quenching constants (KSV) calculated by fluorescence quenching data revealed a non-covalent interaction between the metal complexes and DNA base pairs. In addition, antimicrobial activity against some important pathogens viz., B. amyloliquefaciens, S. aureus, E. coli, K. pneumoniae, S. rolfsii and M. phaseolina have shown that the complexes are more potent than the free ligands. The antioxidant activity of metal complexes have also been determined using DPPH assay and found that the complexes are acted as good free radical scavengers.

A series of binary metal complexes [M(L1)2] and [M(L2)2], (where M = Cu(II), Co(II), Ni(II)) of Schiff bases, HL1 = 2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-4-methylphenol, HL2 = 2-((E)-(4-(trifluoromethoxy)phenylimino)methyl)-5-methoxyphenol, were synthesized and characterized by different analytical and spectral techniques. The spectral studies revealed that the complexes possess a square planar arrangement around the metal ions. DNA binding studies were investigated against calf thymus DNA and found that the compounds bound to DNA through an intercalation mode. The role of compounds in oxidative and photolytic cleavage of supercoiled pBR322 DNA was considered and emphasized that the complexes can cleave the DNA efficiently. The antioxidant activity of ligands and their complexes was evaluated by DPPH assay method and observed that the complexes found to be potent free radical scavengers. Finally, the in vitro antimicrobial activities by paper disc methods have shown that the complexes are more biocidally active than the free Schiff base ligands.