Chandana Sen

Synthesis and structural characterization of a Cu(II)-based 1D coordination polymer and its application in Schottky devices

A new Cu(II) based one-dimensional coordination polymer (1D CP), [Cu(fum)(4-phpy)2(H2O)] (1) (H2fum = fumaric acid and 4-phpy = 4-phenyl pyridine), has been synthesized and well characterized using elemental analysis, infrared spectra, single crystal X-ray diffraction (SCXRD) techniques, powder X-ray diffraction (PXRD) patterns, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). In the solid state structure, 1D chains are self-assembled through strong intermolecular hydrogen bonding to give a 2D sheet structure. These 2D sheets are further accumulated to fabricate 3D supramolecular aggregates via weak CH⋯π interactions. The band gap measurement which is equivalent to the HOMO–LUMO gap calculated by density functional theory (DFT) computations confirms the semiconducting properties of the material. To gain insight into the charge transport mechanism of the compound, its mobility, lifetime and diffusion length have been estimated. The analysis indicates that compound 1 may be applied in active electronic devices. Finally, a metal–CP junction Schottky barrier diode has been successfully fabricated and studied in detail.

Imine-functionalized thioether Zn(II) turn-on fluorescent sensor and its selective sequential logic operations with H2PO4−, DFT computation and live cell imaging

The diformyl thioether Schiff base (H2L) exhibits fluorescent sensing behaviour towards Zn2+ with a limit of detection (LOD) of 0.050 μM, which is far below the WHO guideline (76 μM) in drinking water. The formation of a 1 : 1 metal-to-ligand complex, [ZnL], has been ascertained by X-ray crystallography, Jobs plot and mass spectra. The fluorogenic complex, [ZnL] (either in situ or a solution of the isolated complex) has shown selective ON–OFF emission toward H2PO4−. A two-input, one-output sequential INHIBIT logic circuit has been constructed from H2L, Zn2+ and H2PO4−. The practical applicability of H2L has been examined by the identification of Zn2+ and H2PO4− in the intracellular fluid of African monkey Vero cells.

The spectroscopic characterization, photochromism of cadmium(II)-iodo complexes of 1-alkyl-2-(arylazo)imidazoles and DFT computation of representative complexes.

[Cd(Raai-C(n)H(2n+1))(μ-I)I]2 and [Cd(Raai-C(n)H(2n+1))2I2] are synthesized by the reaction of CdI2 with 1-alkyl-2-(arylazo)imidazole (Raai-C(n)H(2n+1), n=4, 6, 8) in MeOH in 1:1 and 1:2 M ratio of salt and ligands, respectively. The complexes have been characterized by spectral data (UV-Vis, IR, (1)H NMR, Mass). The coordinated Raai-C(n)H(2n+1) shows photochromism, E(trans)-to-Z(cis) isomerisation, upon UV light irradiation. The reverse process, Z-to-E, is very slow in visible light irradiation process while the reaction is sensitive to change of reaction temperature. The quantum yields (ϕE→Z) for E-to-Z and the activation energy (Ea) of Z-to-E isomerisation are calculated and found that the complexes show subordinate results compared to free ligand. DFT computations of two representative complexes were carried out to explain the spectral and photochromic phenomena.

Doubly end-on azido bridged mixed-valence cobalt trinuclear complex: spectral study, VTM, inhibitory effect and antimycobacterial activity on human carcinoma and tuberculosis cells

Doubly end-on azido-bridged mixed-valence trinuclear cobalt complex, [Co3(L)2(N3)6(CH3OH)2] (1) is afforded by employing a potential monoanionic tetradentate-N2O2 Schiff base precursor (2-[{[2-(dimethylamino)ethyl]imino}methyl]-6-methoxyphenol; HL). Single crystal X-ray structure reveals that in 1, the adjacent Co(II) and Co(III) ions are linked by double end-on azido bridges and thus the full molecule is generated by the site symmetry of a crystallographic twofold rotation axis. Complex 1 is subjected on different spectral analysis such as IR, UV-vis, emission and EPR spectroscopy. On variable temperature magnetic study, we observe that during cooling, the χMT values decrease smoothly until 15K and then reaches to the value 1.56 cm(3) K mol(-1) at 2 K. Complex 1 inhibits the cell growth on human lung carcinoma (A549 cells), human colorectal (COLO 205 and HT-29 cells), and human heptacellular (PLC5 cells) carcinoma cells. Complex 1 exhibits anti-mycobacterial activity and considerable efficacy on Mycobacterium tuberculosis H37Rv ATCC 27294 and H37Ra ATCC 25177 strains.

The structure and photophysics of di-iodo-zinc(II) complexes of long alkyl chain substituted imidazolyl motif of arylazoimidazoles and the DFT computation.

Distorted tetrahedral structure of [Zn(Haai-C10H21)2I2] (Haai-C10H21, 1-decayl-2-(arylazo)imidazole) has been supported by single crystal X-ray diffraction study. The structures of other complexes, [Zn(Raai-CnH2n+1)2I2] (n=10, 12, 14, 16, 18, 20, 22) have been determined by spectroscopic data (FT-IR, UV-vis, (1)H NMR). The complexes show light induced photoisomerisation, E-to-Z (trans-to-cis) of coordinated, Raai-CnH2n+1. The Z-to-E (cis-to-trans) isomerisation is also carried out by thermal activation route. The quantum yields of the E→Z progression (ϕE→Z) of the complexes are less than that of free ligand, which could be due to increase in molar mass and molar volume of the complexes than that of free ligands. The activation energy (Ea) of Z→E isomerisation of the complexes is is less than that of free ligands. This observation is also consistent with femtosecond transient absorption results which suggests that the E(trans)→Z(cis) isomerization occurs through the motion of pendant NNAr of the molecule. The temporal profiles of free ligand shows three decay processes corresponds to 0.24ps (S2 state) and subsequent decay, 0.85ps of the S1 state and finally 5ps to the hot ground state at 500nm. The complexes also show three decay periods approximately at 0.25ps, 1.3ps and 13ps. The spectral property and photochromic efficiency have been explained by DFT computation of optimized geometry of the complexes.