Chromogenic hydrazide Schiff base reagent: Spectrophotometric determination of CN- ion.

A Schiff base reagent, Picolinohydrazide-naphthol (HL), is used for trace level detection of toxic CN- selectively in presence of eighteen other anions (SCN-, OCN-, S2O32-, HPO42-, H2PO4-, I-, ClO4-, HSO4-, SO42-, AsO43-, NO2-, AsO2-, Cl-, F-, HF2-, NO3-, Br-, N3-) by visual color change, colorless to yellow, in DMSO/H2O (9:1, v/v) at pH, 7.2 (HEPES buffer) medium. The sensitivity of the probe shows that the limit of detection (LOD) is 7.08 µM. The probable mechanism for the sensing behavior involves the deprotonation of naphthol-OH by CN- that has been authenticated by 1H NMR titration and Mass spectra. The composition (1:1 mol ratio) is supported by Job's plot and binding constant (Ka, 1.5 × 104 M-1) is reported by Benesi-Hildebrand plot. Furthermore, a simple paper strip device is fabricated for the determination of CN- ion in water. DFT computation is carried out to explain the electronic spectral feature of the sensor.

Surface Enhanced Raman Scattering Study of 1-H-2 (tolylazo) Imidazole (TaiH) Induced by Uncoupled Plasmon of Silver Nano Particles.

Raman and SER spectra of 1-H-2 (tolylazo) imidazole (Tai H) are reported for the first time. Monomolecular layer of TaiH is formed on silver nano particles (SNPs) at a concentration of 4.93×10-6 M in Ag-sol. TaiH molecules are adsorbed on to SNPs the through the imidazole N atom and undergo trans-to-cis dark isomerization as evidenced by the appearance of signature cis-peaks and the UV-Vis absorption spectra. Stable non-aggregated SNPs are resulted by the interaction of TaiH and the particle size is significantly reduced. DFT calculations based on single Ag-atom model are in excellent agreement with experimental observations.

EPR interpretation, magnetism and biological study of a Cu(II) dinuclear complex assisted by a schiff base precursor.

A new Cu(II) dinuclear complex, Cu2L2 (1) was afforded employing the potentially pentatentate Schiff base precursor H2L, a refluxed product of o-vanillin and diethylenetriamine in methanol. Complex 1 was systematically characterized by FTIR, UV-Vis, emission and EPR spectrometry. The single crystal X-ray diffraction analysis of 1 reveals that the copper atom exhibits a distorted square planar geometry, comprising two pairs of phenolato-O and imine-N donors from two different H2L ligands. The temperature dependent magnetic interpretation agrees with the existence of weak antiferromagnetic interactions between the bridging dinuclear Cu(II) ions. A considerable body of experimental evidence has been accumulated to elucidate the magneto-structural relationship in this dinuclear Cu(II) complex by DFT computation. Both the ligand and complex 1 exhibit anti-mycobacterial activity and considerable efficacy on M. tuberculosis H37Ra (ATCC 25177) and M. tuberculosis H37Rv (ATCC 25618) strains. The practical applicability of the ligand and complex 1 has been examined in living cells (African Monkey Vero Cells). The MTT assay proves the non-toxicity of the probe up to 100 mg mL-1. A new homometallic dinuclear Cu(II) complex is afforded with a tetradentate Schiff base precursor. EPR interpretation and temperature dependent magnetic studies show that complex 1 has weak antiferromagnetic coupling and DFT computation is governed to explain the magneto-structural correlation.

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.

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 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.