a b s t r a c tAn electronically active and spectral sensitive fluorescent "turn-on" chemosensor (BTP-1) based on the benzo-thiazolo-pyrimidine unit was designed and synthesized for the highly selective and sensitive detection of Fe 3 þ from aqueous medium. With Fe 3 þ , the sensor BTP-1 showed a remarkable fluorescence enhancement at 554 nm (λ ex ¼314 nm) due to the inhibition of photo-induced electron transfer. The sensor formed a host-guest complex in 1:1 stoichiometry with the detection limit down to 0.74 nM. Further, the sensor was successfully utilized for the qualitative and quantitative intracellular detection of Fe 3 þ in two liver cell lines i.e., HepG2 cells (human hepatocellular liver carcinoma cell line) and HL-7701 cells (human normal liver cell line) by a confocal imaging technique.

An imatinib intermediate, 6-methyl-N-[4-(pyridin-3-yl)pyrimidin-2-yl]benzene-1,3-diaminepyridopyrimidotoluidine (PPT-1), was developed for the colorimetric sensing of Cu(2+) ions in aqueous solution. With Cu(2+), the receptor PPT-1 showed a highly selective naked-eye detectable color change from colorless to red over the seventy other tested cations. The colorimetric sensing ability of PPT-1 was successfully utilized in the preparation of test strips and supported silica for the real samples analysis to detect Cu(2+) ions from 100% aqueous environment. Moreover, the iodide-sensing ability of receptor PPT-1 was explored among the ten examined anions.

The pyridine substituted thiourea derivative PTB-1 was synthesized and characterized by spectroscopic techniques as well as by single crystal X-ray crystallography. The metal ion sensing ability of PTB-1 was explored by various experimental (naked-eye, UV-Vis, fluorescence, mass spectrometry and H NMR spectroscopy) and theoretical (B3LYP/6-31G**/LANL2DZ) methods. PTB-1 exhibited a highly selective naked-eye detectable color change from colorless to dark brown and UV-Vis spectral changes for the detection of Ag with a detection limit of 3.67 μM in aqueous medium. The detection of Ag ions was achieved by test paper strip and supported silica methods. In contrast, PTB-1 exhibited a 23-fold enhanced emission at 420 nm in the presence of Hg ions with a nano-molar detection limit of 0.69 nM. Finally, the sensor PTB-1 was applied successfully for the intracellular detection of Hg ions in a HepG2 liver cell line, which was monitored by the use of confocal imaging techniques.

An amidine based chemosensor AM-1 was synthesized and characterized by various spectroscopic (FT-IR, (1)H-NMR and mass) data and elemental analyses. Sensor AM-1 exhibited high selectivity and sensitivity towards Fe(3+), Fe(2+) and Cu(2+) in the presence of other surveyed ions (such as Sr(2+), Cr(3+), Co(2+), Ni(2+), Zn(2+), Ag(+), Al(3+), Ba(2+), Ca(2+), Cd(2+), Cs(+), Hg(2+), K(+), Li(+), Mg(2+), Mn(2+), Na(+) and Pb(2+)) with a distinct naked-eye detectable color change and a shift in the absorption band. Moreover, the emission of AM-1 was quenched selectively only in the presence of Fe(3+).

A simple uracil nitroso amine based colorimetric chemosensor (UNA-1) has been synthesized and screened for its cation recognition ability.

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A novel fused benzothiazolo-pyrimidine based optical chemosensor 4-imino-2-methylsulphanyl-4H-9-thia-1,4a-diaza-fluorene-3-cabonitrile (BTP-1) was designed and synthesized efficiently for the selective recognition of Fe 3 + and I À ions from the aqueous medium. Sensor BTP-1 selectively recognizes Fe 3 + ions through the quenching of fluorescence emission intensity at 454 nm and I À ions through a hyperchromic shift in UV-Vis spectra. The recognition of both Fe 3 + and I À ions was found free from the interference of other inspected cations and anions, respectively.[a] N.