Soumik Mandal

Synthesis and characterization of two Cu(II) complexes with a new pyrazole-based Schiff base ligand: crystallography, DNA interaction and antimicrobial activity of Ni(II) and Cu(II) complexes

Abstract Reaction of Cu(II) nitrate with a new pyrazole-based Schiff base ligand, 5-methyl-3-formylpyrazole-N-(2′-methylphenoxy)methyleneimine (MPzOA), afforded two types of Cu(II) complexes at different reaction temperatures, [Cu(MPzOA)(NO3)]2 (1) and [Cu(3,7,11,15-tetramethylporphyrin)(H2O)](NO3)2 (2), reported together with a Ni(II) complex, [Ni(MPzOA)2(H2O)2]Br2 (3). The compounds are characterized by single crystal X-ray structure analyses along with several physico-chemical and spectral parameters. Complex 1 is authenticated as a bis(μ-pyrazolato)dicopper(II), while 2 is a porphyrinogen and 3 is a distorted octahedral complex. Structural analyses of the complexes reveal that 1 crystallized in monoclinic P21/n space group while 2 and 3 crystallized in monoclinic C2/c space group. DNA-binding studies of the complexes have shown that the complexes interact with CT-DNA. DNA-cleavage studies with plasmid DNA have shown that 1 and 2 induce extensive DNA cleavage in the presence of H2O2 as an additive, whereas there is no change in degradation of super-coiled DNA by 3 in the presence of additive. The antimicrobial studies of the complexes against Escherichia coli DH5α bacteria strain indicated that all the complexes were capable of killing E. coli with different LD50 values.

Organoiridium complexes: efficient catalysts for the formation of sugar acetals and ketals.

[Cp(∗)IrCl(2)](2) is used as an efficient promoter for the synthesis of sugar acetals and ketals with good to excellent yields. The catalyst is found to be general for a wide range of sugars.

Interaction of semicarbazide and thiosemicarbazide pyrene derivatives with anionic and cationic micelles: changed character of pyrene due to alteration in charge density induced by the side chains

A semicarbazide and a thiosemicarbazide derivative of pyrene have been synthesized keeping in mind the pharmaceutical potentiality of the molecules. The molecules differ in structure only at the CO and the CS groups. The presence of the amine group in the vicinity of the O and the S atoms distributes the π-electrons in the pyrene differently making the pyrene moiety in the semicarbazide more hydrophobic than that in the thiosemicarbazide. Because of this different electron distribution in the ground state of the molecules, they interact variably with either cationic or anionic micelles. The compounds are found to attach to the cationic micelles at the surface through electrostatic interactions between the pyrene electrons and the surfactant head groups, varying in the strength of the binding. The exaggerated electron density towards the S counterpart in the thiosemicarbazide drives the molecule to move to the Stern layer, whereas, due to a greater electron cloud over the pyrene moiety of the semicarbazide it stays inside the palisade layer of the anionic micelle. We have used fluorescence spectroscopy to investigate the interactions. The different extents of the distribution of these medically potent compounds in biomimicking cationic and anionic micelles could further open up their biological applications.

Bis{μ-(E)-methyl 4-[(2-carbamothio-ylhydrazinyl-idene)meth-yl]benzoate-κS:S}bis-[iodido(triphenyl-phosphane-κP)copper(I)].

The title complex, [Cu2I2(C10H11N3O2S)2(C18H15P)2], is a centrosymmetric sulfur-bridged dimer of CuI with PPh3 and iodine. The CuI atom shows a distorted tetrahedral geometry, with bite angles ranging from 98.61 (2) to 120.16 (3)°. The intramolecular Cu⋯Cu distance is 2.8228 (12) Å. The thiosemicarbazone ligand is coordinated only through the S atom. In the crystal, the complex molecules are linked via intermolecular N—H⋯O hydrogen bonds, resulting in a hydrogen-bonded chain along the b axis.

Methyl 4-(1H-benzimidazol-2-yl)benzoate trihydrate.

The title compound, C15H12N2O2·3H2O, has been prepared from the reaction of a Schiff base of benzene-1,2-diamine and iron perchlorate at room temperature. The dihedral angle between the benzimidazole ring and the 4-substituted benzene ring is 0.47 (3)°. Hydrogen bonding involving water molecules, imidazole N, imidazole imine H and ester O atoms stabilizes the crystal structure.