Here, naphthalene diamine-based β-diketone derivative (compound LH) was successfully used as a dual signaling probe for divalent cations, Fe2+ and Cu2+ ions, in bimodal methods (colorimetric and fluorometric). It showed fluorescent enhancement for Fe2+ ion by photoinduced electron transfer mechanism and fluorescence quenching for Cu2+ ion by charge-transfer process. Binding stoichiometry for [LH–(Fe2+)2] and [LH–(Cu2+)2] was found to be 1:2 by Job’s plot method and, the binding constants were calculated as 1.6638 × 1010 and 9.22929 × 108 M–1, respectively. Compound LH exhibited OR and XOR logic gate behavior with H+, Fe2+, and Cu2+ as inputs. Further, the compound LH and bovine serum albumin binding interaction showed quenching of fluorescence by Forster resonance energy-transfer mechanism.

On/Off Fluorescent Chemosensor for Selective Detection of Divalent Iron and Copper Ions: Molecular Logic Operation and Protein Binding

A fluorescent chemical sensor based on a bis(salamo)-like tetraoxime H2LS was designed and synthesized. The chemical sensor uses double N2O2 cavities as sensing elements, which can be combined with specific metal ions to achieve ion recognition. The chemical sensor can detect Cu2+ by the phenomenon of fluorescence quenching, and a test strip loaded with the sensor is used to quickly and accurately identify Cu2+. Besides, the chemical sensor also can continuously recognize Al3+ in the system and realize the interference-free identification effect of other trivalent metal ions on Al3+. Through 1H NMR, mass spectrometry, infrared spectroscopy, and other experiments, the identification mechanism of the fluorescent chemical sensor was verified. The numerical values of LOD and Ka were calculated by the corresponding titration data and Benesi-Hildebrand formula.

Fluorescent chemical sensor based on double N2O2 cavities for continuous recognition of Cu2+ and Al3+

β-Cyclodextrin (β-CD) is a nontoxic cyclic oligosachcharide that can encapsulate all or part of organic molecules of appropriate size and specific shape through noncovalent interaction. Herein, we report the influence of β-CD complex formation of an antipyrine derivative on its metal ion sensing behavior. In aqueous solution, the antipyrine shows a turn-on fluorescence sensing of vanadyl ion, and in cyclodextrin medium it senses aluminum ion. The compound shows an unusual fluorescence quenching on binding with β-cyclodextrin (log KSV = 2.34 ± 0.02). The differential metal ion sensing is due to the partial blocking of the chelating moiety by the cyclodextrin molecule. The structure of the antipyrine–cyclodextrin complex is optimized by two-dimensional rotating-frame Overhauser effect spectroscopy. The binding constant is determined by isothermal titration calorimetry (log K = 2.09 ± 0.004). The metal ion binding site is optimized by quanutm mechanical calculations. The lower limit of detection of vanadyl a...

Differential Metal Ion Sensing by an Antipyrine Derivative in Aqueous and β-Cyclodextrin Media: Selectivity Tuning by β-Cyclodextrin.

For the first time, we have reported the metal ion sensing behaviour of a fluorescent probe APAP (derivative of 4-amino/4-formyl antipyrine) along with its precursors (AAP-4-Aminoantipyrine, FAP-4-Formylantipyrine) and explained the tuning of precursors resulted in difference in the sensing behaviour. The two antipyrine precursors (4-amino/4-formyl antipyrine) were condensed together to form a new host molecule APAP, which acts an effective fluorescent chemosensor for detection of Fe3+ ions. The precursors AAP and FAP would able to detect Al3+ and Cr3+ ions respectively. The antipyrine precursors as well as the antipyrine derivative showed fluorescence response towards trivalent cations when treated with various metal ions in CH3OH:H2O (1:9, v/v) medium. Binding stoichiometry between APAP and Fe3+ ion was 1:1 from Jobs’ plot and the binding constant value was calculated as 5.3 × 105 M−1 by Benesi–Hildebrand plot. Addition of Na2EDTA to the [APAP-Fe3+] complex solution quenched the fluorescence emission, indicating the reversible nature of the probe. The binding of APAP with Fe3+ was based on restricted PET with CHEF process. Quantum mechanical studies using time dependent density functional theory (TDDFT) have also been carried out to understand the mechanism of Fe3+ binding mode with APAP probe. With respect to various pH, the probe APAP exhibited an AND molecular logic gate behaviour when H+ and Fe3+ ions were given as inputs. For the first time, the metal recognition property of a fluorescent probe along with its precursors was studied.

Evaluation of metal ion sensing behaviour of fluorescent probe along with its precursors: PET-CHEF mechanism, molecular logic gate behaviour and DFT studies

Aqueous Zn2+ analysis: Specific recognition and instant imaging by Schiff base fluorescent probes

Vanadium compounds exhibit anti-tumor properties and insulin-like activity, but an excess is toxic Development of a selective fluorescent chemosensor for the detection of vanadyl ions has not been reported so far For the first time, we have reported an effective fluorescent chemosensor C1 for selective recognition and detection of vanadyl ions C1 was evaluated as a turn “ON” fluorescent chemosensor for vanadyl ions (VO2+) based on a photoinduced electron transfer (PET) mechanism The association constant for the complex C1–VO2+ was found to be 419 × 104 M−1 C1 also behaves as a NOT molecular logic gate where H+ and VO2+ were given as inputs The proposed binding mode between C1 and vanadyl ions was explained using DFT calculations

G. Tamilselvan

Papers

Evaluation of metal ion sensing behaviour of fluorescent probe along with its precursors: PET-CHEF mechanism, molecular logic gate behaviour and DFT studies

The first highly selective turn “ON” fluorescent sensor for vanadyl (VO2+) ions: DFT studies and molecular logic gate behavior