Senjuti Mandal

A new pyridoxal based fluorescence chemo-sensor for detection of Zn(II) and its application in bio imaging

This paper describes the activity of a Schiff base ligand, derived from pyridoxal, as a promising fluorescence probe for biologically important Zn(II) ion sensing. A physiologically compatible pyridoxal based chemosensor PydDmen was synthesized and evaluated for its fluorescent response towards metal ions. Chemosensor PydDmen exhibits a selective turn-on type response in the presence of Zn2+ in ethanol–water mixture. The addition of EDTA quenches the fluorescence of receptor PydDmen-Zn2+, making the chemosensor PydDmen reversible. The response is specific for Zn(II) ions, and remains almost unaffected by the presence of alkali and alkaline earth metals but is suppressed to varying degrees by transition metal ions. The selectivity mechanism of PydDmen for Zn2+ is the combined effects of proton transfer between the prevailing tautomeric forms, CN isomerization and CHEF. The DFT optimized structure of the complex is compatible with elemental analysis, mass spectrometry, FT-IR, electronic and NMR spectra. The experimental and theoretical support in terms of NMR spectroscopy and DFT are provided to establish the existence of Zn2+ induced transformation of PydDmen to a 3-pyridone tautomeric form.

Syntheses, crystal structures, spectral studies, and DFT calculations of two new square planar Ni(II) complexes derived from pyridoxal-based Schiff base ligands

Two new complexes based on a Schiff base derived from pyridoxal N,N-dimethylethylenediamine (HL1) and N,N-diethylethylenediamine (HL2), [Ni(L1)SCN] (1) and [Ni(L2)SCN] (2), have been synthesized and structurally characterized by single-crystal X-ray diffraction along with other physical techniques, including elemental analyses, IR spectra, cyclic voltammetry, UV–vis, and luminescence studies. X-ray studies suggest that in both the complexes nickel lies in a slightly distorted square planar environment occupied by the tridentate ONN ligand and an isothiocyanate moiety. Density functional theory computations have been carried out to characterize the complexes. Two new square planar Ni(II) complexes, [Ni(L1)SCN] (1) and [Ni(L2)SCN] (2) are synthesized from pyridoxal-based Schiff base ligands and structurally characterized. DFT calculations are also done to establish their optimized electronic structures.

Bis{2-[(5-hy­droxy­pent­yl)imino­meth­yl]phenolato-κ2N,O1}copper(II)

In the title compound, [Cu(C12H16NO2)2], the CuII ion, located on a center of inversion, is coordinated by two singly deprotonated Schiff base ligands derived from condensation of salicyldehyde and 1-aminopentan-5-ol. The imino N and phenol O atoms from both ligands offer a square-planar arrangement around the metal ion. The Cu—N and Cu—O bond lengths are 2.0146 (15) and 1.8870 (12) Å, respectively. Since the Cu—O and Cu—N bond lengths are different, it can be concluded that the resulting geometry of the complex is distorted. The aliphatic –OH group of the ligand is not coordinated and points away from the metal coordination zone and actively participates in hydrogen bonding connecting two other units and thus stabilizing the crystal lattice. This results in a two-dimensional extended array parallel to (201).