Anup Paul

pH dependent synthesis of Zn(II) and Cd(II) coordination polymers with dicarboxyl-functionalized arylhydrazone of barbituric acid: photoluminescence properties and catalysts for Knoevenagel condensation

Four novel Zn(II) and Cd(II) compounds based on a dicarboxyl-functionalized arylhydrazone of barbituric acid ligand, 5-[2-{2,4,6-trioxotetrahydropyrimidin-5(2H)-ylidene}hydrazinyl]isophthalic acid (H5L), namely [Zn(1κO:2κO′:3κO′′-H3L)(H2O)2]n (1), [Cd(1κO,O’:2κO′:3κO′′,O′′′-H3L)(H2O)2]n (2), [Zn(κN-H3L)(H2O)3]·3H2O (3) and [Cd(1κO,O′:2κN-H3L)(H2O)3]n·4nH2O (4), have been synthesized at different pHs under hydrothermal conditions and characterized by elemental and thermogravimetric, FT-IR, and X-ray single-crystal diffraction analyses. Compounds 1 and 2 prepared in acidic medium are coordination polymers exhibiting double chain type one-dimensional (1D) structures, whereas 3 and 4 are obtained in basic medium. Compound 3 is a mononuclear Zn(II) complex containing three lattice water molecules, but in 4, Cd(II) cations are bridged by H3L2− ligands to form an interesting zig-zag type 1D coordination polymer. The crystal structures of these compounds are stabilized by strong hydrogen bonding interactions, forming two and three-dimensional networks. The pH value of the reaction system plays a crucial role in the ligand deprotonation and in the assembly of the metal–organic polymers. These compounds act as effective heterogeneous catalysts, under mild conditions, for the Knoevenagel condensation reaction of different aldehydes with malononitrile and can be recycled at least five times without losing activity. Further, compounds 1–4 exhibit luminescence properties in the solid state at room temperature.

Potential apoptosis inducing agents based on a new benzimidazole schiff base ligand and its dicopper(II) complex

Synthesis, characterization and antiproliferative activity of a new benzimidazole based Schiff base 2-(1-methyl-1-H-benzimidazol-2-yl)phenyl)imino)methyl)phenol (HL) and dicopper(II) complex [{Cu(L)NO3}2] (CuL) containing L− has been described. Both HL and CuL have been meticulously characterized by satisfactory elemental analyses, FT-IR, NMR, ESI-MS, electronic absorption and emission spectroscopy, and their structures unambiguously determined by X-ray single crystal analyses. Titration studies (absorption and emission) revealed interaction of the ligand and its dicopper(II) complex with DNA/BSA and stronger affinity of the CuL relative to HL. Binding of the HL and CuL with DNA/BSA have been validated by in silico studies and their cytotoxic effect on human breast cancer cell lines (MCF-7) by MTT assay. IC50 values (458 μM and 22 μM for HL, CuL) clearly suggested substantial cytotoxicity of the complex CuL toward MCF-7 compared to the ligand HL. Greater antiproliferative efficacy of the CuL in contrast to HL has been evidenced by fluorescence activated cell sorting (FACS) and AO/EB fluorescence staining. The possible mode of the apoptotic pathway for CuL has further been affirmed by reactive oxygen species (ROS) generation studies.

Nanoporous lanthanide metal–organic frameworks as efficient heterogeneous catalysts for the Henry reaction

A series of self-assembled lanthanide coordination polymers formulated as [La(L1)2]n·1n(DMF)H·3n(DMF) (1), [Ce(L1)2]n·1n(DMF)H·2n(DMF) (2), [Sm(L1)2]n·1n(HCONH2)H·2n(HCONH2) (3), [La(L2)(HL2)(H2O)(DMF)2]n (4) and [Ce(L2)(HL2)(H2O)(DMF)2]n (5) [H2L1: 2-acetamidoterephthalic acid and H2L2: 2-benzamidoterephthalic acid] has been synthesized from the reactions of H2L1 or H2L2 with different lanthanide salts under hydrothermal conditions and characterized by elemental analysis, IR spectroscopy, X-ray single-crystal diffraction, powder X-ray diffraction, thermogravimetry and photoluminescence spectroscopy. X-ray diffraction analyses reveal that frameworks 1–3 have similar types of three-dimensional structures, composed of L12− ligands and trinuclear lanthanide nodes, in which two crystallographically independent lanthanide atoms are present. Frameworks 4 and 5 are isostructural, featuring a double chain-type one-dimensional coordination polymer which expands to 3D by means of H-bond interactions. These frameworks act as heterogeneous polymeric solid catalysts for the nitroaldol (Henry) reaction of different aldehydes with nitroalkanes, in water, and can be recycled without losing appreciable activity.

Amide functionalized metal–organic frameworks for diastereoselective nitroaldol (Henry) reaction in aqueous medium

The two new metal–organic frameworks (MOFs) of zinc(II) and copper(II) [Zn2L2(1,4-BDC)]n·2n(DMF) (1) and [Cu(L)2]n·4n(DMF)·n(H2O) (2) (L = 4-(pyridin-4-ylcarbamoyl)benzoate; BDC = benzenedicarboxylate), respectively, have been synthesized from a pyridyl amide functionalized benzoic acid (HL). They were characterized by elemental, FT-IR, thermogravimetric, powder X-ray and single crystal X-ray diffraction analyses. Single crystal X-ray crystallography reveals that 1 and 2 exhibit 2D and 3D polymeric architectures, respectively. Topological analysis illustrates a 6-connected pcu alpha-Po primitive cubic topology for 1 and an 8-connected body centred cubic (bcu) topology for 2. Both 1 and 2 act as heterogeneous catalysts for the nitroaldol reaction in aqueous medium, with a high yield and moderate to good diastereoselectivities under ambient conditions. They can be recycled and reused without any significant loss of the catalytic efficiency.

Recent advances on supramolecular isomerism in metal organic frameworks

Metal–organic frameworks (MOFs) or coordination polymers (CPs), a class of compounds constructed often by self-assembly of inorganic metal ions and organic ligands, have attracted growing interest on account of their diverse structures, permanent porosity and tunable properties, with a prospect for various applications. In some cases, the self-assembly of the building blocks produces different MOFs with the same molecular composition, i.e., supramolecular isomers. The design of supramolecular isomers in the area of MOFs is challenging and this highlight gathers recently published articles concerning the different types of supramolecular isomers, i.e., structural, conformational, catenane and optical, in this area. The syntheses and structures of the isomers and their comparison are presented, as well as the role of various parameters, such as temperature, solvent, concentration, crystallization method, additive and template, in the formation of the different supramolecular isomers, by analyzing selected examples.

Application of atomic and nuclear techniques to the study of inhomogeneities in electrodeposited α-particle sources

Three α-particle sources made by different methods of electrodeposition were analysed using α-particle spectrometry, Rutherford backscattering (RBS), and atomic force microscopy (AFM) on several surface zones. The thickness and homogeneity of these sources was studied using RBS, and the results were analysed jointly with those obtained with α-particle spectrometry and AFM techniques. The comparison of the electrodeposition methods showed that the most homogeneous electrodeposited zones corresponded to the source made with a stirring cathode.

Unfolding biological properties of a versatile dicopper(II) precursor and its two mononuclear copper(II) derivatives

Synthesis, inter-conversions and biological study of the dichloro bridged dicopper(II) compound [CuLCl]2 (1) and its two mononuclear derivatives [CuLCl(H2O)]·H2O (2) and [CuLCl(py)] (3) (HL=2-(2-pyridylmethyleneamino)benzenesulfonic acid) are described. The dimeric compound 1 collapses into monomers 2 and 3 in the presence of coordinating solvents, water and pyridine, respectively, and 1 is regenerated upon simple stirring of 2 or 3 in methanol. The reactions of 1 with neutral (present study) and charged (earlier studies) ligands result in monomeric and multimeric compounds, respectively, attesting that it is a versatile dicopper(II) precursor. The anticancer activity of these copper complexes (1-3) was screened against lung (A-549) and breast (MDA-MB-231) human cancer cell lines. The IC50 (half maximal inhibitory concentration) value for one (3) of the compounds suggests preferential cytotoxicity against breast cancer MDA-MB-231 cell line. Furthermore, the IC50 value obtained for complex 3 is found to be almost two-fold times cytotoxic than the standard drug cisplatin. In addition, the underlying possible mechanism of its apoptosis-inducing efficacy in MDA-MB-231 cells has been rationalized by using flow cytometry (FACS) and Hoechst 33342/propidium iodide (PI) fluorescence staining. The stimulation of apoptotic induction for complex 3 has further been affirmed by reactive oxygen species (ROS) generation and mitochondrial aggregations studies.