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Vanillinyl‐hydrazone Schiff base, 2,6‐Bis‐[(2‐hydroxy‐3‐methoxy‐benzylidene)‐hydrazonomethyl]‐4‐methyl‐phenol (PHV) is characterized by spectroscopic techniques and serves as selective and sensitive fluorescence sensor at different emission wavelength for Zn2+ (λem, 546 nm), Cd2+ (λem, 567 nm) and Mg2+ (λem, 625 nm) in DMSO/H2O medium (9 : 1, v/v) in presence of large number of available cations. The probe also displays selective turn‐on fluorescence sensitivity to I− (λem, 635 nm) in THF medium. Density Functional Theory (DFT) computation techniques are used to explain some of the obtained experimental observation. [ABSTRACT FROM AUTHOR]

(E)-N′-((7-Hydroxy-4-methyl-2-oxo-2H-chromen-8-yl)methylene)picolinohydrazide (H-CPh), a greenish yellow emitter in the solid state, aggregates in DMSO solution upon increasing the percentage of water (>50%) and the maximized emission intensity was reached at 90% water–DMSO medium. Upon excitation at 400 nm in pure aquatic medium (HEPES buffer, pH 7.2) H-CPh shows fluorescence sensitivity to Al3+ (λem, 470 nm) and forms a 1 : 1 complex, [(CPh)Al(OH)(H2O)]NO3, with a limit of detection (LOD) of 6.99 nM. The complex, [(CPh)Al(OH)(H2O)]NO3 shows sensitivity to nitroaromatics by quenching the strong emission of the fluorogenic complex and the LODs are: 2,4-dinitrophenol (DNP), 1.67 μM and 2,4,6-trinitrophenol (TNP) 0.99 μM. The H-CPh is electronically a semiconductor and the experimental (2.78 eV) and the DFT derived (2.75 eV) band gaps are comparable. The H-CPh forms a Schottky diode and its photoconductivity (19.98 × 10−4 S m−1) is three times higher than the dark phase conductivity (6.42 × 10−4 S m−1). [ABSTRACT FROM AUTHOR]

Herein, the vanilinyl-picolinyl hydrazide dyad Schiff base (HVPh) was structurally characterized by single-crystal X-ray diffraction crystallography. The molecule exhibits an intense green fluorescence in the solid state and serves as a solvent-tuned dual detector to Mg2+ and Al3+ and a secondary sensor to HF2−. Mg2+ imparts a yellow emission at 522 nm (LOD, 45 nM) in DMSO, whereas an intense blue emission is observed for Al3+ in pure water at 460 nm (LOD, 7.4 nM). The probe formed a 1 : 1 complex with Al3+ and a 1 : 2 complex with Mg2+, and the composition of these complexes was established by NMR, mass and FTIR spectral data. Studies on the anion sensitivity of these complexes showed that HF2− efficiently quenched the emission of the complexes, and the LODs were far below the WHO recommended data (Mg2+, 200 mM; Al3+, 7.41 mM; and F−, 3.68 μM). A recovery study was performed to check the practical applicability of the probe using drinking water supplied by Kolkata Municipality Corporation in the Jadavpur University campus. The molecular INHIBIT logic gate was also constructed by the sensor. The DFT and TDDFT computation techniques were used to explain the experimental findings. [ABSTRACT FROM AUTHOR]

Coumarinyl-rhodamine, HCR, served as an extremely selective sensor for Pd2+ ions in ethanol/H2O (8 : 2, v/v, HEPES buffer, pH 7.2) solution and the limit of detection (LOD) was 18.8 nM (3σ method). The free sensor, HCR, was weakly emissive and in the presence of Pd2+, the colour changed from straw to pink with very strong emission at 598 nm in the presence of eighteen other cations. A plausible mechanism involved opening of the spirolactam ring of rhodamine on interaction with Pd2+, which was justified by structure optimization and transition energy calculations using the DFT technique. HCR underwent 1 : 1 complexation with Pd2+, which was confirmed via the Job's plot, mass spectra and Benesi–Hildebrand plot (association constant Ka, 9.1 × 104 M−1). A separate in vitro experiment showed that HCR could specifically sense Pd2+ in MCF7 (human breast adenocarcinoma) cell lines. [ABSTRACT FROM AUTHOR]

6,6′-((1E,1′E)-((2E,2′E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(hydrazine-2,1-diylidene))bis(methanylylidene))bis(3-methoxyphenol). (H3L) is a multi-responsive vanilinyl-p-cresol diformyl Schiff base fluorescent chemosensor for Zn2+ (λem, 545 nm), Cd2+ (λem, 560 nm) (both in 9 : 1 (v/v) DMSO–water), and I− (λem, 630 nm in THF). The probe (H3L) is spectroscopically characterised and the chemosensing mechanism is demonstrated through 1H NMR, ESI-MS, absorption and luminescence spectral data. The most promising advantage of the probe (H3L) is its application in the one-pot detection of Zn2+ and Cd2+ using excitation at the same wavelength (λex, 482 nm) while highly intense emission appears at two different wavelengths. A detection kit is designed for drinking water analysis and has been checked to measure the quality of potable water in the locality. The sensor is also applied to construct an INHIBIT logic gate. Density Functional Theory (DFT) calculations are used to optimize the structure and the electronic properties are correlated with the experimental results. [ABSTRACT FROM AUTHOR]

6,6′-((1E,1′E)-((2E,2′E)-((2-hydroxy-5-methyl-1,3-phenylene)bis(methanylylidene))bis(hydrazine-2,1-diylidene))bis(methanylylidene))bis(3-methoxyphenol). (H3L) is a multi-responsive vanilinyl-p-cresol diformyl Schiff base fluorescent chemosensor for Zn2+ (λem, 545 nm), Cd2+ (λem, 560 nm) (both in 9 : 1 (v/v) DMSO–water), and I− (λem, 630 nm in THF). The probe (H3L) is spectroscopically characterised and the chemosensing mechanism is demonstrated through 1H NMR, ESI-MS, absorption and luminescence spectral data. The most promising advantage of the probe (H3L) is its application in the one-pot detection of Zn2+ and Cd2+ using excitation at the same wavelength (λex, 482 nm) while highly intense emission appears at two different wavelengths. A detection kit is designed for drinking water analysis and has been checked to measure the quality of potable water in the locality. The sensor is also applied to construct an INHIBIT logic gate. Density Functional Theory (DFT) calculations are used to optimize the structure and the electronic properties are correlated with the experimental results. [ABSTRACT FROM AUTHOR]

2,6-Bis(N-ethylhydrazonethiocarbamide)-4-methyl-phenol (HTP) recognizes PO43− and AsO33− and is effective as a colorimetric and turn-on fluoremetric sensor in the presence of a large number of biologically important cations and anions. The limit of detection (LOD) is 34 nM for PO43− and 15 nM for AsO33−. The composition of the probe–anion association has been established by Job's plot, 1H-NMR titration and HR-MS data. The Density Functional Theory (DFT) computation technique is used to optimize the structure that has been compared with an X-ray structure of HTP and the calculated electronic properties are correlated with the experimental results. Turn-on detection of PO43− and AsO33− is also successfully utilized for the fabrication of an ‘OR’ gate. The probe, HTP, is used for analysis of the ground water of Jadavpur, Kolkata. [ABSTRACT FROM AUTHOR]

The efficiency of the fluorescence sensitivity of a sensor may be tuned by the modulation of the steric and electronic parameters in the structure. In this study, the thiophenyl Schiff base (E)-N 1 -(phenyl(pyridin-2-yl)methyl)-N 2 -(thiophen-2-ylmethylene)benzene-1,2-diamine (HL') exhibited very high selectivity and a sensitive fluorescence enhancement towards Fe 3+ with violet emission (λ em , 385 nm; LOD, 3.8 nM). On the other hand, the naphthyl Schiff base (E)-1-(((2-((phenyl(pyridin-2-yl)methyl)amino)phenyl)imino)methyl)naphthalen-2-ol (H 2 L'') exhibited fluorescence sensitivity towards Al 3+ , showing blue emission (λ em , 502 nm; LOD, 3.3 nM) in H 2 O (HEPES buffer, pH 7.4) medium. The emission enhancement of HL' upon binding to Fe 3+ may be considered to be due to the restriction of intramolecular rotation, while the selectivity of H 2 L'' towards Al 3+ may be due to the turn on emission through the restriction of excited state intramolecular proton transfer (ESIPT) and the introduction of chelation enhanced fluorescence (CHEF). Furthermore, DFT computation supported the sensing strategy and the probes were applied for intracellular detection of Fe 3+ and Al 3+ in HepG2 cell lines.

( E )- N '-((2-Hydroxynaphthalen-1-yl)methylene)picolinohydrazide (H-PNAP) shows aggregation-induced emission (AIE) strictly in a 90% water/MeOH (v/v) mixture at 540 nm, and the solid-state emission is blue-shifted to 509 nm upon excitation at 400 nm. The AIE activity of H-PNAP is selectively quenched by 2,4,6-trinitrophenol (TNP) and 2,4-dinitrophenol (DNP) out of different nitroaromatic compounds with a limit of detection (LOD) of 7.79 × 10 -7 and 9.08 × 10 -7 M, respectively. The probe is nonemissive in aqueous medium (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, HEPES buffer, pH 7.2); however, it shows a strong emission to Al 3+ (λ em , 490 nm) in the presence of 17 other biological metal ions, and the LOD is 2.09 nM which is far below the WHO recommended value (7.41 mM). The emission of the [Al(PNAP)(NO 3 ) 2 ] complex is quenched by HF 2 - (F - and PO 4 3- are weak quencher), and the LOD is as low as 15 nM. The probable mechanism of the sensing feature of the probe has been authenticated by 1 H nuclear magnetic resonance titration, mass spectrometry, Fourier transform infrared spectroscopy, Benesi-Hildebrand plot, and Job's plot in each case. The probe has some practical applications such as recovery of Al 3+ from the drinking water sample, construction of the INHIBIT logic gate, and detection kits for Al 3+ and TNP/DNP by simple paper test strips. The probe, H-PNAP, has successfully been applied to the detection of intracellular Al 3+ and HF 2 - ions in the human breast cancer cell, MDA-MB-468., Competing Interests: The authors declare no competing financial interest.