Mrigendra Dubey

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.

A schiff base and its copper(II) complex as a highly selective chemodosimeter for mercury(II) involving preferential hydrolysis of aldimine over an ester group

The syntheses of a new Schiff base, diethyl-5-(2-hydroxybenzylidene)aminoisophthalate (HL), and a copper complex, [Cu(L2)] (1), imparting L(-), have been described. Both the ligand HL and complex 1 have been thoroughly characterized by elemental analyses, electrospray ionization mass spectrometry, FT-IR, NMR ((1)H and (13)C), electronic absorption, and emission spectral studies and their structures determined by X-ray single-crystal analyses. Distinctive chemodosimetric behavior of HL and 1 toward Hg(2+) has been established by UV/vis, emission, and mass spectral studies. Comparative studies further revealed that the chemodosimetric response solely originates from selective hydrolysis of the aldimine moiety over the ester group and 1 exhibited greater selectivity toward Hg(2+) relative to HL while the sensitivity order is reversed. Further, these followed different hydrolytic pathways but ended up with the same product analyzed for diethyl-5-aminoisophthalate (DEA). Hg(2+)-induced displacement of Cu(2+) and subsequent hydrolysis of the -HC═N- moiety in 1 affirmed the identity of the actual species undergoing hydrolysis as HL. The occurrence of Cu(2+) displacement and Hg(2+) detection via hydrolytic transformation has been supported by various physicochemical studies.

Li+-induced selective gelation of discrete homochiral structural isomers derived from L-tartaric acid

Two chiral structural isomers have been synthesized by molecular engineering of L-tartaric acid. In the presence of LiOH isomer forms a thermally stable, fluorescent gel which exhibits interesting nano-cluster morphology, anomalous optical and rheological properties whilst forms a non-fluorescent solution under similar conditions. The current-voltage (I-V) curve followed a non-linear trend, rationally in close proximity to the diode characteristic curve.

Size-controlled synthesis of Ag nanoparticles functionalized by heteroleptic dipyrrinato complexes having meso-pyridyl substituents and their catalytic applications

The syntheses of heteroleptic dipyrrinato nickel(II) complexes [Ni(4-pydpm)(dedtc)] (1) and [Ni(4-pydpm)(dipdtc)] (2) [4-pydpm = 5-(4-pyridyl)dipyrromethene; dedtc = diethyldithiocarabamate; and dipdtc = diisopropyldithiocarbamate] and the thorough characterization of these complexes by satisfactory elemental analyses, electrospray ionization mass spectrometry, Fourier-transform infrared, NMR ((1)H, (13)C), and UV-vis spectroscopies, and electrochemical studies was achieved. Structure of 1 was authenticated by X-ray single-crystal analysis. Both the complexes 1 and 2 were successfully utilized as a capping agent in the preparation of silver nanoparticles. Availability of free pyridyl nitrogen on the dipyrrin core of these complexes was meticulously exploited in functionalization and stabilization of the silver nanoparticles (AgNPs). Morphological and structural investigations on colloidal nanoparticles were followed by UV-vis spectroscopy and transmission electron microscopy (TEM). Overall results revealed that average size of the silver nanoparticles (∼10, 15, 20 nm, and aggregation) is strongly influenced by ratio of Ag/[1/2] (03, 06, 10, 20). Correlation between particle size and capping agents was realized by UV-vis and TEM studies. Catalytic activity of the AgNPs obtained through this route was successfully employed in the reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP). It was established that reduction process follows a pseudo-first-order kinetics.

Detection of copper(II) and aluminium(III) by a new bis-benzimidazole Schiff base in aqueous media via distinct routes

The synthesis is described of a new bis-benzimidazole appended Schiff base ligand [2-(3,5-bis(1H-benz-imidazol-2-yl)-phenyliminomethyl)phenol] (H3L) followed by its thorough characterization by elemental analyses, spectroscopic studies (FT-IR, 1H, 13C NMR, ESI-MS, UV/vis, fluorescence) and X-ray single crystal analyses. The excellent selectivity of H3L towards Cu2+ and Al3+ via distinct responses in mixed aqueous conditions was established by spectroscopic studies. The selective detection of Cu2+ due to the creation of complex 1 in which Cu2+ occupied only the salen-type N2O2 coordination site and the strong binding with Al3+ through both benzimidazole and salen moieties to yield complex 2 was confirmed by various studies. The disparate detection of these cations by H3L was substantiated by comparative studies, performed under analogous conditions, of the precursor compound 3,5-bis(1H-benzimidazol-2-yl)-aniline (BBA). The distinct interaction of H3L with Cu2+ and Al3+ and the sensing mechanisms were investigated in detail by spectroscopic studies and were supported by theoretical studies (Density Functional Theory). It has been clearly shown that the use of appropriate substituents may facilitate the design and development of probes suitable for the real time detection of more than one analyte.

Retention of Cs–Cl bond induces coordination polymer formation over trinuclear chiral assembly of copper(II) complexes of L-leucine derived ligand

The use of caesium is a less trodden path in terms of the synthesis of coordination polymers. The chemical similarity and mild toxic nature of caesium salts does not provide much impetus to work with these compounds compared to their potassium analogues. However, are the potassium and caesium salts really close in terms of coordination polymer formation? The result presented in this manuscript shows that while neither potassium halides or potassium nitrate inhibit the formation of a trinuclear chiral assembly of a copper(II) complex from a mononuclear Cu(II) complex, caesium chloride preferentially forms a coordination polymer while keeping the Cs–Cl bond intact. Under the same conditions, caesium nitrate does not inhibit the assembly formation. Structural characterization of {[CsCl{Cu(HLL-leu)2}(H2O)]}n (2) showed it to be a two-dimensional coordination polymer in the ab plane, where penta-coordinated Cu(HLL-leu)2 complex units (HLL-leu = reduced Schiff base of L-leucine and the salicylaldehyde condensation product) were interconnected through the formation of Cu–Cl–Cs bonds. Multitudes of intermolecular H-bonds were observed as well. The use of KCl, KBr, KI or CsNO3 in lieu of CsCl to the [Cu(HLL-leu)2(CH3CN)] (1) facilitated the formation of the trinuclear assembly, [M{Cu(HLL-leu)2}3]X, where M = K+ or Cs+ and X = Cl, Br, I or NO3 depending on the salt used. The Cu(HLL-leu)2 units in these assemblies are hexacoordinated Cu(II) complexes.