Anandaram Sreekanth

DNA/protein binding, DNA cleavage, cytotoxicity, superoxide radical scavenging and molecular docking studies of copper(II) complexes containing N-benzyl-N′-aryl-N′′-benzoylguanidine ligands

Five copper(II) complexes containing N,N′,N′′-trisubstituted guanidine ligands were synthesized and characterized by elemental analyses and UV-Visible, FT-IR, EPR and mass spectroscopic techniques. The synthesized copper(II) complexes (1–5) bear the general formula [Cu{C6H5CONC(NR)NHCH2C6H5}2] where R = phenyl (1), 4-methylphenyl (2), 4-ethoxyphenyl (3), 2-methoxyphenyl (4) or 1-naphthyl (5). The four coordinated square planar geometry of the complexes was confirmed by the single crystal X-ray diffraction study. The interaction of the Cu(II) complexes with calf thymus DNA (CT DNA) was explored using absorption and fluorescence spectroscopic methods. The results revealed that the complexes have an affinity constant for DNA in the order of 104 M−1 and the mode of interaction is non-covalent intercalation. The DNA cleavage study showed that the complexes cleaved DNA without any external agent. The interaction of Cu(II) complexes with bovine serum albumin (BSA) was also studied using absorption and fluorescence techniques. The cytotoxic activity of the Cu(II) complexes was probed in vitro against human breast (MCF7) and lung (A549) cancer cell lines. The complexes were also tested against mouse embryonic fibroblast (NIH 3T3) cell lines. Complexes 1 and 3 have good cytotoxic activity which is comparable with the cyclophosphamide drug. The complexes were less cytotoxic towards normal cell lines showing that they affect only cancer cell lines. Superoxide radical scavenging property of the complexes was assessed using the NBT assay. Copper(II) complexes showed appreciable superoxide radical scavenging activity with IC50 values ranging from 1.53 to 5.62 μM. A further molecular docking technique was employed to understand the binding of the complexes toward the molecular target DNA and human DNA topoisomerase I.

Synthesis, X-ray crystal structure, DNA/protein binding and DNA cleavage studies of novel copper(II) complexes of N-substituted isatin thiosemicarbazone ligands

A new series of N-substituted isatin thiosemicarbazone ligands (L1–L5) and their copper(II) complexes [Cu(II)(ITSC)] (1–5) were synthesized and characterized by elemental analyses, UV-Visible, FT-IR, 1H and 13C NMR/EPR and mass spectroscopic techniques. The molecular structures of L1–L5, and 3 were confirmed by single crystal X-ray crystallography. The X-ray diffraction studies of the complexes revealed a square planar geometry. The interaction of calf thymus (CT) DNA and bovine serum albumin (BSA) with the copper(II) complexes was explored using absorption and emission spectral methods. Spectral evidence showed the intercalative mode of DNA binding with the copper(II) complexes. The DNA cleavage study showed that the complexes cleaved DNA without any external agents. Spectral evidence also supported the binding property of the complexes with the protein. The alterations in the secondary structure of the protein by the copper(II) complexes (1–5) were confirmed by synchronous and three-dimensional fluorescence spectroscopic studies.

Spectroscopic and DFT investigations on the corrosion inhibition behavior of tris(5-methyl-2-thioxo-1,3,4-thiadiazole)borate on high carbon steel and aluminium in HCl media

The effect of tris(5-methyl-2-thioxo-1,3,4-thiadiazole)borate (HB(mtdaMe)3) on the corrosion of high carbon steel (HCS) and aluminium (Al) in HCl media has been examined by Electrochemical Impedance Spectroscopy (EIS), polarization (Tafel), Scanning Electron Microscopy (SEM), X-ray Photoelectron Spectroscopy (XPS), Electronic spectroscopy and adsorption kinetics methods. The polarization studies show that HB(mtdaMe)3 acts as a cathodic inhibitor for HCS, while it is a mixed type inhibitor of predominantly the cathodic reaction in Al. The inhibition efficiency of the compound is very high and the SEM and XPS results have revealed that HB(mtdaMe)3 is adsorbed on the HCS and Al surface. The adsorption of HB(mtdaMe)3 on the HCS and Al surface obeys the Langmuir adsorption isotherm. DFT calculations were used to gain insight into the structural and electronic properties in relation to the inhibition efficiency.

Multi-ion detection and molecular switching behaviour of reversible dual fluorescent sensor

The selective chemosensing behaviour of imidazole bisthiocarbohydrazone (IBTC) towards F- and Cu2+ are studied via colorimetric, UV-Visible, fluorescence spectra studies, and binding constants were calculated. The 1H NMR titration study strongly support that the deprotonation of IBTC followed by the hydrogen bond formation via N1H1 and N2H2 protons with fluoride ion. The fluorescence inactive IBTC-Cu complex became fluorescence active in the presence of perchlorate (ClO4-) ion. The selective detection of perchlorate ion was also explained. The F- sensing mechanism of IBTC has been investigated by Density Functional Theory (DFT) and Time-Dependent Density Functional Theory (TDDFT) methods. The theoretical outcomes well reproduce the experimental results. And it concluded the NH protons, nearby the imine group was first captured by the added F- ion and then deprotonation happened followed by the formation of hydrogen bond. The IBTC found good reversibility character with the alternative addition of Ca2+ and F-. The multi-ion detection of IBTC was used to construct the NOR, OR and INHIBITION molecular logic gates.

Crystal structure of 3-[(E)-(2-hy­droxy-3-meth­oxy­benzyl­idene)amino]-1-methyl-1-phenyl­thio­urea

The asymmetric unit comprises two independent molecules. In the crystal, the two independent molecules are linked by bifurcated N—H⋯O hydrogen bonds, forming a supramolecular chain with a (14)[(5)] motif.