Arghyadeep Bhattacharyya

Highly sensitive and selective “naked eye” sensing of Cu(II) by a novel amido–imine based receptor: a spectrophotometric and DFT study with practical application

We report the synthesis of a novel compound (E)-bis-N′-((1H-pyrrol-2-yl)methylene)-pyridine-2,6-carbohydrazide and its sensing ability to detect copper(II) ion in aqueous medium by a sharp color change from yellow to brown, the sensing limit being 4.0 × 10−9 M. Theoretical modeling of the compound and its copper complex was performed. Practical utility was explored by successful paper strip response.

Hydrazine bridged coumarin-pyrimidine conjugate as a highly selective and sensitive Zn2 + sensor: Spectroscopic unraveling of sensing mechanism with practical application

We report the synthesis and Zn2+ sensing of a novel coumarin-hydrazine conjugate 3-{1-[(4, 6-Dimethyl-pyrimidin-2-yl)-hydrazono]-ethyl}-chromen-2-one (3). Compound 3 can act as a neat fluorescent Zn2+ sensor by an increment in fluorescence intensity along with an appreciable red shift. Fluorescence enhancement is caused by complexation through cis-trans isomerization process in the presence of Zn2+ ion. The practical utility of 3 was demonstrated by successful test kit experiment to detect Zn2+ in water under UV-light.

Selective chromo-fluorogenic molecular sensor for dual channel recognition of Cu2+ and F−: effect of functional group on selectivity

The sensor HNHCB (3-hydroxy-naphthalene-2-carboxylic acid (4-cyano-benzylidene)-hydrazide) comprises a –CONH– group, –OH group, –CHN– linkage and an electron withdrawing –CN group that can act as both an anion (fluoride) and a cation (copper) sensor by two distinct output modes. It can detect fluoride by naked eye color change and copper by fluorescence enhancement. Interestingly, the nature of the substituent in HNHCB has an effect on the selectivity. The detection limit can be as low as 160 nM for Cu2+ and 1.3 μM for F−. DFT calculations have been performed to demonstrate the structure of HNHCB and its copper complex. Biological applications of HNHCB have been evaluated in HEK 293 and it was found to exhibit membrane permeability for the detection of Cu2+. The sensor HNHCB is also sensitive towards fluoride in commercially available toothpaste.

Harnessing a pyrimidine based molecular switch to construct reversible test strips for F−/AcO− with respect to Al3 +: A colorimetric approach

We report novel compound 4-nitro-2-((pyrimidin-2-ylamino) methyl) phenol (1) synthesized by the condensation of 5-nitro salicylaldehyde with 2-amino pyridine. Compound 1 serves as a dual signalling chromogenic receptor for F-/AcO- and Al3+ ions. The chromogenic response of 1 towards the aforementioned analytes is reversible with respect to either Al3+/X (=F/AcO)- or X(F/AcO)-/Al3+. The limit of detection of 1 for F- and AcO- are 1.0025×10-7M and 0.79×10-7M, respectively. The optical switching has been rationalized on the basis of UV-Vis titrations and 1H NMR titrations respectively. The optical switching has been successfully use by constructing reversible paper strips for detecting Al3+ as well as F-/AcO-.

Employing a hydrazine linked asymmetric double naphthalene hybrid for efficient naked eye detection of F−: Crystal structure with real application for F−

An asymmetric hydrazide, (12E, 13E)-2-((naphthalen-1-yl) methylene)-1-(1-(2-hydroxynaphthalen-6-yl) ethylidene) hydrazine (abbreviated as AH) is synthesized and characterized by standard techniques and crystal structure of AH has been obtained. The naked eye detection of F- in aqueous acetonitrile (acetonitrile: water=7:3/v:v) by AH has been investigated by UV-Visible titration and in presence of other anions, the limit of detection being 1.31×10-6(M). The mechanism of F- sensing has been explored by 1H NMR titration. AH undergoes hydrogen bonding with F- followed by deprotonation. The practical utility of AH has been explored by successful test kit response and color change in toothpaste solution.

CHEF-Affected Fluorogenic Nanomolar Detection of Al3+ by an Anthranilic Acid–Naphthalene Hybrid: Cell Imaging and Crystal Structure

We report the synthesis of a novel hydrazine-bridged anthranilic acid–naphthalene conjugate (E)-2-(benzamido)-N′-((2-hydroxynaphthalen-1-yl) methylene) benzohydrazide (BBHAN) and its crystal structure. BBHAN can detect Al3+ by a sharp increment in fluorescence intensity (∼40 times) in aqueous methanolic medium. The limit of detection of BBHAN towards Al3+ is 1.68 × 10–9 M, and the former undergoes a 2:1 binding with Al3+ with a high binding constant of ∼1.15 × 1011 M2–. BBHAN detects Al3+ by the well-known mechanism of chelation-enhanced fluorescence (CHEF), established by fluorescence time-resolved measurement. The mode of interaction between BBHAN and Al3+ has been explored by 1H NMR and electrospray ionization mass spectrometry techniques. Paper strips coated with BBHAN can detect Al3+ under UV light observed through the naked eye. Lastly, BBHAN can detect Al3+ in MDA-MB-468 cells.