Lallan Mishra

The importance of cellular localisation of probes: synthesis, photophysical properties, DNA interactions and cellular imaging properties of rhenium dppz complexes with known cellular localisation vectors

The synthesis, photophysical properties, DNA binding, DNA cleavage and cellular imaging behaviour of a range of complexes of the type [Re(CO)3(dppz)(PyR)]+ are reported, where PyR represents a range of substituted pyridines which have previously been studied for cellular localisation of related complexes. Confocal imaging experiments confirm that the complexes retain the variety of cellular localisation behaviour associated with the PyR units in other complexes, and suggest applications as probes for oligonucleotides in specific cellular compartments (e.g. mitochondrial DNA). This study illustrates the importance of considering cellular localisation as a prime consideration in the design of probes for in vivo application.

Synthesis, spectroscopic, electrochemical and antibacterial studies of new Ru(II) 1,10-phenanthroline complexes containing aryldiazopentane-2,4-dione as co-ligand

Mononuclear and dinuclear Ru(II) complexes of 1,10-phenanthroline containing aryldiazopentane-2,4-diones (L1H–L3H2) as co-ligands were prepared and characterised using IR, 1H NMR, UV/Vis spectra in addition to their elemental analysis and FAB mass spectral data. A representative ligand L2H2 and its complex [Ru2L2(phen)4]2+ (phen=1,10-phenanthroline) were characterised also by 1H–1H COSY, TOCSY and 1H–13C HMBC spectral data. Electrochemical behaviour of the complexes was studied in acetonitrile solution and showed irreversible RuII/RuIII redox couples. Luminescence and UV/Vis spectral properties of the complexes in the presence and absence of buffered solutions of calf thymus DNA were also compared. Antibacterial activity of the complexes has been evaluated against Pseudomonas aeruginosa.

Antitumor and antimicrobial activities of Fe(II)/Fe(III) complexes derived from some heterocyclic compounds

The antitumor activities of some Fe(II)/Fe(III) complexes containing 1,3-diacetyl-2H-benzimidazole-2-thione along with a few derivatives of 1,2,4-triazol, 1,3,4-oxadiazole and 1,3,4-thiadiazole as co-ligands have been investigated. Antibacterial and antifungal activities of disulfido-/dichloro-bridged dinuclear Fe(III)/Fe(II) complexes containing similar heterocycles as terminal ligands have also been investigated.

SYNTHESIS, SPECTROSCOPIC AND ANTIFUNGAL STUDIES OF TRANSITION METAL TRINUCLEAR/POLYNUCLEAR COMPLEXES WITH AZOLO-2,4-PENTANEDIONE : PART III

Azolo (thiazolo and triazolo)-2,4-pentanedione (L1 and L2) were condensed with o-phenylenediamine in the presence of the chloride salts of nickel(II), copper(II) and palladium(II). The resulting trinuclear/polynuclear complexes were characterized by elemental analysis, conductance and magnetic moments (room temperature and variable temperature) as well as i.r., u.v.–vis., 1H-n.m.r. and e.s.r. spectra.

Tuning of Aggregation Enhanced Emission and Solid State Emission from 1,8-Naphthalimide Derivatives: Nanoaggregates, Spectra, and DFT Calculations.

Four new 1,8-naphthalimide based compounds, 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-benzoic acid (LH), 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-benzoic acid methyl ester (LMe), 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-benzoyl chloride (LCl), and 4-(1,3-dioxo-1H,3H-benzo[de]isoquinolin-2-ylmethyl)-benzoic acid hydrazide (LN) are synthesized and characterized using spectral data and X-ray crystallography. They form nanoaggregates in aqueous-DMF solution and exhibited aggregation enhanced emission. The nanoaggregates are characterized using their scanning electron and atomic force microscopy images. The emission intensity follows the order as LH > LMe > LCl > LN. Their photophysical properties are recorded both in solution and in the solid-state and are correlated with the nature of benzoic acid derivatives owing to the combinatorial effect of π-π stacking and intermolecular and intramolecular interactions. The density functional theory calculations empower the understanding of their molecular and cumulative electronic behaviors. Antiparallel dimeric interactions in the solid-state extend a herringbone arrangement to LH and 2D channel and stair-like arrangement for LCl and LN, respectively.

Neuroprotective Role of a Novel Copper Chelator against Aβ 42 Induced Neurotoxicity.

Alzheimers disease (AD) is a progressive neurodegenerative disease and associated with the extracellular deposits of amyloid-β peptide in hippocampus region. Metal ions like Cu, Fe and Zn are known to associate with the amyloid beta (Aβ) at high concentration and interaction of these ions with soluble and aggregated forms of Aβ peptide help in development of AD. Here we showed Cu mediated neurotoxicity in the eye tissues of transgenic Drosophila expressing human amyloid β and its rescue through a novel Cu chelator. In this context, we have synthesised and characterized the compound L 2,6-Pyridinedicarboxylic acid, 2,6-bis[2-[(4-carboxyphenyl) methylene] hydrazide] by Mass spectra (MS) and Elemental analysis (EA). The Cu chelation potential of the compound L is tested in vivo in Drosophila. Oral administration of Copper to the transgenic larvae resulted in severe degeneration in eye tissues, which was rescued by the supplementation of compound L. The levels of anti-oxidant markers like SOD and MDA were measured in compound L treated flies and found a significant rescue (P < 0.001). Further rescue of the eye degeneration phenotypes as revealed by SEM affirm the role of copper in Aβ toxicity. Hence, use of compound L, an amidoamine derivative, could be a possible therapeutic measure for Aβ induced neurotoxicity.

Studies on Some New Ru(III) Complexes Using aryl-azo Pentane- 2,4-dione and 2,6-bis (2'-Benzimidazolyl) Pyridine as Ligands: Synthesis, Spectroscopic, Luminescent, Electrochemical and Biological Activities.

Some ruthenium(III) complexes with aryl-azo 2,4-pentanedione as co-ligands (L1H - L3H2) have been synthesized and characterized spectroscopically IR, 1H NMR, UV/Vis, ESR, conductimetric) along with elemental analysis and FAB-mass data. Their luminescent and redox properties have been studied. The antibacterial, anti-HIV and antitmnour activities have also been reported.

A new rhodamine derivative as a single optical probe for the recognition of Cu2+ and Zn2+ ions

A bifunctional colorimetric and fluorescent chemosensor of type 3,5-dinitro-2-hydroxy benzaldehyde rhodamine hydrazone (RHDN) was synthesized by the condensation of 3,5-dinitro salicylaldehyde and rhodamine B hydrazide. It was characterized using spectroscopic techniques and single crystal studies. The chemosensor RHDN exhibited remarkably enhanced absorbance and colour changes from colourless to pink color on binding with Cu2+ ions. In contrast, Zn2+ ions were identified by their selective binding with RHDN showing OFF–ON type fluorescence, which changes from colorless to orange color in ultra violet-light. The absorbance and emission pattern of RHDN adduct separately with Cu2+ and Zn2+ ions were restored with the addition of an aqueous solution of disodium salt of ethylenediaminetetraacetic acid. Thus, RHDN was found to be very robust and reversible in its binding with Cu2+ and Zn2+ ions separately.

Bi-nuclear Ru(II) complexes of bis-chalcone and bis-flavonol: synthesis, characterization, photo cleavage of DNA and Topoisomerase I inhibition

Complexes of type [Ru2(L1/L2)(DMSO)6Cl2] (L1H2 = 1-(2-Hydroxy-phenyl)-3-{4-[3-(2-hydroxy-phenyl)-3-oxo-propenyl]-phenyl}-propenone 1, L2H2 = 1,4-bis-(3-hydroxy-4-oxo-4H-chromen-2-yl)-benzene) 2, are prepared and characterized using spectroscopic techniques. In complex 1, both ruthenium centres possess a similar coordination environment in which all S-dmso coordinate to ruthenium centres. However, in complex 2, one ruthenium centre is coordinated to three S-bonded dmso, and other ruthenium ion is coordinated to two S-bonded dmso and one O-bonded dmso. This difference in coordination around ruthenium centres in complex 2 is supported by two irreversible oxidation peaks observed at 0.84 V and 1.06 V and two MLCT transitions observed at λmax 485 and 565 nm in its cyclic voltammetry and UV-visible spectrum respectively. The interaction of complexes with Calf Thymus DNA (CT-DNA) is monitored using UV–vis titrations (Kb = 2.1 × 106 M−1 for 1 and 1.3 × 105 M−1 for 2) and ethidium bromide displacement studies (Ksv = 1.37 and 0.98). The stronger binding of complex 1 with CT-DNA as compared to complex 2 could be attributed to its conjugated structural framework. In presence of complex 1 under photo-induced condition in visible region at λ 560 nm, supercoiled DNA is converted more in nicked circular form and supported its stronger binding with DNA as compared to complex 2. Complexes intercalate (1 stronger than 2) with DNA. They also prefer minor groove (1) and major groove (2) binding with DNA. Both complexes inhibit topoisomerase I relaxation activity at concentration > 50 μM.

Binding of Urea and Thiourea with a Barbiturate Derivative: Experimental and Theoretical Approach

A barbiturate derivative [1,5-dihydro-5-[5-pyrimidine-2,4(1H,3H)-dionyl]-2H-chromeno[2,3-d] pyrimidine-2,4(3H)-dione)] (L1) possesses functionalities complementary to amide and thioamide. Hence its binding with urea and thiourea, is monitored using UV-vis and fluorescence titrations as well as isothermal titration calorimetry (ITC) study. Theoretical studies on hydrogen-bonded complexes of L1-urea and L1-thiourea in the gas phase, aqueous, and DMSO medium are carried out using density functional theory (DFT) at the B3LYP/6-31G** level. The theoretical calculations support the experimental results.