Niraj Kumari

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.

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.

A light/pH/multiple ion-driven smart switchable module for computing sequential logic operations via a resettable dual-optical readout

A switchable module comprising pendant pyridine groups, an amide linkage and a photoswitchable functionality (azobenzene) has been designed and characterized via a full battery of physico-chemical techniques. The module has been exploited for ternary/binary data storage with non-destructive optical identity owing to its high photo-stability, excellent reversibility, and chemical-/photo-switchability. Moreover the module exhibits sequential logic gate-based detection of multiple ions (Cu2+, CN−, F− and I−) at ppm levels via a “turn on” signature which potentially meets real-world challenges in terms of the simple synthesis route, rapid response, water based activity, naked-eye visualization, regenerative action, high selectivity and multiple readout for precise analysis.

Azobenzamide-based proteomorphous objects as a light/pH-induced photoswitchable module

Azobenzamide-based molecular scaffolds viz. (E)-4,4′(diazene-1,2-diyl)bis(N-pyridin-3-yl)benzamide (1) and (E)-4,4′(diazene-1,2-diyl)bis(N-pyridin-4-yl)benzamide (2), yield proteomorphous architectures i.e., secondary “β-pleated sheet” and tertiary “β-hairpin” respectively, that offer “optical data storage” competence as a result of reversible light-induced conformational changes in organic solvent.

Correction: Fluorescein hydrazone-based supramolecular architectures, molecular recognition, sequential logic operation and cell imaging

A fluorescein hydrazone (FDNS) is prepared by the coupling of fluorescein hydrazide with 3,5-dinitrosalicylaldehyde. It is well characterized using spectroscopic (IR, UV-visible, 1H, 13C NMR, ESI-MS) techniques and X-ray crystallography. FDNS is embedded with several H-bonding domains which provide interesting intra and inter molecular H-bonded networks. Its crystal packing along the b crystallographic axis using H-bonding interactions provides a fascinating helical structure. It detects Cu2+ ions selectively over many relevant ions and displays a novel peak at λmax = 495 nm. The significant enhancement in its fluorescence is observed with a peak at λem = 517 nm on addition of Hg2+ ions, which is quenched upon the addition of S2− ions. The sensing of Hg2+ ions by FDNS follow a hydrolysis pathway whereas the binding of Cu2+ ions with FDNS provides a colour change. The addition of a solution of tetrabutylammoniumcyanide in methanol to a corresponding solution of FDNS caused a turn to a green colour immediately. But on keeping the solution at room temperature for 72 h, red coloured crystals are obtained. The crystals were authenticated by X-ray crystallography. It was found to be a new compound FKCN in which a tetrabutylammonium cation is co-crystallized with deprotonated FDNS. Its supramolecular assembly via H-bonding provides an interesting ladder type architecture. FDNS displays chronological logic gate-based detection of several ions (Cu2+, Hg2+, EDTA, and S2−) at ppm levels. The real sample analysis, live cell imaging and portable paper strip based detection of Cu2+ and Hg2+ ions via an obvious colour change endows FDNS with great economic significance in recognition processes.

Thiocyanato Bridged Heterodinuclear Complex [Cu(bpy)2(µ-NCS)Ru(bpy)2(NO3)](PF6)2 and Its Binding with Cd(II), Hg(II), Pb(II) and Ag(I) Ions

The precursor complexes of composition [Cu(bpy)2(H2O)](PF6)2 1 and [Cu(bpy)2(NCS)](PF6) 2 (bpy = 2,2′-bipyridine) were initially prepared and characterized using spectroscopic (IR, UV-vis, ESR, Emission) along with their mass, elemental analysis, and single crystal X-ray crystallographic data. Complex 2 is linked with a known complex Ru(bpy)2(NO3)2 prepared in situ. The resulting heterobimetallic complex of composition [Cu(bpy)2(μ-NCS)Ru(bpy)2(NO3)](PF6)2 3 was isolated and characterized by its spectroscopic, mass, and elemental analysis data and its geometry is optimized without any constraint with plane-wave ab initio density functional theory using solid state package Abinit. The emission and electrochemical properties of these complexes are studied. The multiresponsive chemosensor property of complex 3 for Hg(II) ions as compared to Cd(II), Pb(II) and Ag(I) ions is monitored using UV-vis and fluorescence titrations.