Abstract:An efficient and environmentally benign synthetic protocol has been developed for the synthesis of benzo[c]pyrazolo[2,7]naphthyridine derivatives through regioselective multi-component “on-water” reaction of isatin, malononitrile and 3-aminopyrazole.
“…The isatins 6 react with malononitrile 7 via Knoevenogel condensation to form arylidenes. The formed arylidenes are then reacted with 3-amino-5-methylpyrazole 8 to synthesize spiro-intermediates which then undergo basic hydrolysis, cyclization, decarboxylation and aromatization to form target naphthyridine receptors (L1–L4) 37 .…”
Highly selective and sensitive 2,7-naphthyridine based colorimetric and fluorescence “Turn Off” chemosensors (L1-L4) for detection of Ni2+ in aqueous media are reported. The receptors (L1-L4) showed a distinct color change from yellow to red by addition of Ni2+ with spectral changes in bands at 535–550 nm. The changes are reversible and pH independent. The detection limits for Ni2+ by (L1-L4) are in the range of 0.2–0.5 µM by UV–Visible data and 0.040–0.47 µM by fluorescence data, which is lower than the permissible value of Ni2+ (1.2 µM) in drinking water defined by EPA. The binding stoichiometries of L1-L4 for Ni2+ were found to be 2:1 through Job’s plot and ESI–MS analysis. Moreover the receptors can be used to quantify Ni2+ in real water samples. Formation of test strips by the dip-stick method increases the practical applicability of the Ni2+ test for “in-the-field” measurements. DFT calculations and AIM analyses supported the experimentally determined 2:1 stoichiometries of complexation. TD-DFT calculations were performed which showed slightly decreased FMO energy gaps due to ligand–metal charge transfer (LMCT).
“…The isatins 6 react with malononitrile 7 via Knoevenogel condensation to form arylidenes. The formed arylidenes are then reacted with 3-amino-5-methylpyrazole 8 to synthesize spiro-intermediates which then undergo basic hydrolysis, cyclization, decarboxylation and aromatization to form target naphthyridine receptors (L1–L4) 37 .…”
Highly selective and sensitive 2,7-naphthyridine based colorimetric and fluorescence “Turn Off” chemosensors (L1-L4) for detection of Ni2+ in aqueous media are reported. The receptors (L1-L4) showed a distinct color change from yellow to red by addition of Ni2+ with spectral changes in bands at 535–550 nm. The changes are reversible and pH independent. The detection limits for Ni2+ by (L1-L4) are in the range of 0.2–0.5 µM by UV–Visible data and 0.040–0.47 µM by fluorescence data, which is lower than the permissible value of Ni2+ (1.2 µM) in drinking water defined by EPA. The binding stoichiometries of L1-L4 for Ni2+ were found to be 2:1 through Job’s plot and ESI–MS analysis. Moreover the receptors can be used to quantify Ni2+ in real water samples. Formation of test strips by the dip-stick method increases the practical applicability of the Ni2+ test for “in-the-field” measurements. DFT calculations and AIM analyses supported the experimentally determined 2:1 stoichiometries of complexation. TD-DFT calculations were performed which showed slightly decreased FMO energy gaps due to ligand–metal charge transfer (LMCT).
“…The isatin 6 react with malononitrile 7 via Knoevenogel condensation to form arylidene. The formed arylidene then reacted with 3-amino-5-methylpyrazole 8 to synthesize the spiro-intermediates which then undergo basic hydrolysis, cyclization, decarboxylation and aromatization to form target naphthyridine receptors (L1-L4) 31 .…”
Section: Resultsmentioning
confidence: 99%
“…The synthesis of receptors (L1-L4) was carried out in two steps following our previously reported protocol 31 Synthesis of L4-Ni 2+ complex…”
A highly selective and sensitive 2,7-naphthyridine based colorimetric, reversible, pH independent and fluorescence “Turn Off” chemosensors (L1-L4) for detection of Ni2+ are being reported in aqueous media. The synthesized sensors are highly efficient in detecting Ni2+ even in the presence of other metal ions that commonly co-exist with nickel. The receptors (L1-L4) showed a distinct color change from yellow to red by addition of Ni2+ with spectral changes in bands at 535–550 nm. The detection limit of Ni2+ for (L1-L4) are in the range of 0.2–0.5 µM which is 2–5 times lower than the permissible value of Ni2+ (1.2 µM) in drinking water defined by EPA. The binding mode of interactions of L1-L4 for Ni2+ were found to be 2:1 through job’s plot and ESI-MS analysis. Moreover the receptors can be used to quantify Ni2+ in real water samples and formation of test strips by dip-stick method increases the practical applicability of Ni2+ test for “in-the-field” measurement of Ni2+. Importantly the sensing potential of these derivatives have been tuned by the nature of substituents i.e. electron donating (CH3) and electron attracting (F, OCF3), which showed that L4 is highly efficient in sensing of Ni2+ even at minute level.
Cancer is one of the leading causes of death worldwide. The increasing prevalence and resistance to chemotherapy is responsible for driving the search of novel molecules to combat this disease. In search of novel compounds with pro-apoptotic potential, pyrazolo-pyridine and pyrazolo-naphthyridine derivatives were investigated against cervical cancer (HeLa) and breast cancer (MCF-7) cells. The anti-proliferative activity was determined through the MTT assay. Potent compounds were then analyzed for their cytotoxic and apoptotic activity through a lactate dehydrogenase assay and fluorescence microscopy after propidium iodide and DAPI staining. Flow cytometry was used to determine cell cycle arrest in treated cells and pro-apoptotic effect was verified through measurement of mitochondrial membrane potential and activation of caspases. Compounds 5j and 5k were found to be most active against HeLa and MCF-7 cells, respectively. G0/G1 cell cycle arrest was observed in treated cancer cells. Morphological features of apoptosis were also confirmed, and an increased oxidative stress indicated the involvement of reactive oxygen species in apoptosis. The compound-DNA interaction studies demonstrated an intercalative mode of binding and the comet assay confirmed the DNA damaging effects. Finally, potent compounds demonstrated a decrease in mitochondrial membrane potential and increased levels of activated caspase-9 and -3/7 confirmed the induction of apoptosis in treated HeLa and MCF-7 cells. The present work concludes that the active compounds 5j and 5k may be used as lead candidates for the development of lead drug molecules against cervical and breast cancer.
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