Explosive and pollutant nitroaromatic sensing through a Cd(II) based ladder shaped 1D coordination polymer.

In the existing leanings of environmental and national security issues, establishment of appropriate sensors for explosive as well as pollutant nitroaromatic compounds may be considered as one of the most prodigious job for material researchers. In the current study a new Cd(II) based 1D ladder coordination polymer (CP), [Cd(4-bpd)(3-cbn)2]n, has been synthesized and well characterized through single crystal X-ray diffraction analysis. Interestingly, the supramolecular assembly of this compound has efficiently identified 2,4,6-trinitrophenol through fluorescence quenching method. The Stern-Volmer coefficient (Ksv) has been calculated as 6.047 × 103 M-1, which can be attributed to the quenching of the emission intensity. The limit of detection (LOD) has been determined as 0.260 µM following the 3σ method along with almost 95% fluorescence intensity reduction. FESEM study revealed that the crystalline nature of the compound has been altered upon interaction with the above mentioned nitroaromatic analyte. Theoretical studies were performed to get the insight idea of fluorescence quenching mechanism which also substantiated the experimental observation. The present study can pave the way for the fabrication of future generation technology in sensor field.

Idiosyncatic recognition of Zn2+ and CN- using pyrazolyl-hydroxy-coumarin scaffold and live cell imaging: depiction of luminescent Zn(II)-metallocryptand.

Multi-responsive and selective sensor design is one of the stimulating research areas in the sensors field. We have designed a pyrazolyl-hydroxy-coumarin scaffold, 7-hydroxy-4-methyl-8-(((5-phenyl-1H-pyrazol-3-yl)imino)methyl)-2H-chromen-2-one (H2L) and characterized it by spectroscopic techniques (1H NMR, 13C NMR, ESI-MS, IR). The single crystal X-ray diffraction measurement confirms the molecular structure of the probe. It shows the selective sensing of Zn2+ in the presence of sixteen other cations with 'Turn On' approach through the enhancement of green florescence ((λem = 499 nm; λex = 390 nm) in CH3CN/H2O (99 : 1, v/v; HEPES buffer, pH 7.5) medium with the limit of detection (LOD) of 34.76 nM. The structural depiction of the isolated Zn2+ complex reveals cage like metallocryptand cyclic hexamer, [Zn6L6] with 30.9% void of cavity along the crystallographic c axis of approximate dimension of 7.502 × 7.050 × 7.068 Å3. The diffusion NMR study reveals only one type of complex in the solution, having 1 : 1 composition, i.e., Zn2+ : H2L, which affirms the isolated form of the complex. On the other hand, the receptor, H2L, recognizes the very noxious anion CN- out of sixteen anions. The product identification using spectroscopic techniques supports the nucleophilic addition of CN- across the exocyclic imine (CN) bond, which shows blue emission ((λem = 447 nm; λex = 390 nm), and the LOD was 19.91 nM. The composition of [H2L-Zn2+] and [H2L-CN-] was established by 1H NMR titration, Job's method, ESI-MS, and FTIR spectra. The efficacy of the probe was further studied using MTT assay in MDA-MB 231 and WI-38 cell line as well as for the intracellular imaging of Zn2+ and CN- using a fluorescence microscope. Flow Cytometry was further performed for the quantitative analysis of Zn2+ distribution in MDA-MB 231 cells.

A highly emissive Zn(II)-pyridyl-benzimidazolyl-phenolato-based chemosensor: detection of H2PO4-via "use" and "throw" device fabrication.

2-Ethoxy-6-[1-(phenyl-pyridin-2-yl-methyl)-1H-benzoimidazol-2-yl]-phenol (HL) selectively serves as a sensitive 'turn on' Zn2+ sensor in 9 : 1 (v/v) DMSO/H2O (HEPES buffer, pH = 7.4) medium in the presence of sixteen other cations at the limit of detection (LOD) of 3.2 nM. The strong blue emission of the complex, {[Zn(L1)OAc]} (HL1 = benzimidazolyl ring-opening structure of HL) (λem, 461 nm), is quenched by H2PO4- in the presence of eighteen other anions and the LOD is 0.238 µM. The emission of the complex is due to restricted intramolecular rotation (RIR) followed by chelation-enhanced fluorescence (CHEF). The quenching of the emission of [Zn(L1)OAc] by H2PO4- (in the presence of other PVs (inorganic and biological) as well as additional anions) is due to the 'turn off' fluorescence via the demetallation and release of the nonfluorescent ligand, HL, and [Zn(H2PO4)]+. An INHIBIT logic gate memory circuit of the probe HL was devised with Zn2+ and H2PO4- as two consecutive inputs. The percentage of H2PO4- recovery was excellent and was obtained from distilled, tap, and drinking water sources. The bright blue emission of [Zn(L1)OAc] further triggered the fabrication of ready-made portable thin films of the Zn-complex, which executed a cost-effective 'on-site' solid-state contact mode detection of H2PO4- with selectivity at the picogram level (10.97 pg cm-2) by monitoring the intensities of quenched spots under UV light upon varying the analyte concentration from 10-8 to 10-3 M. Finally, taking advantage of reversible fluorescence switching, a simple and definite ion-responsive security feature was successfully embedded into a "use" and "throw" solution-coated paper strip of the Zn(II)-pyridyl-benzimidazolyl-phenolato-based chemosensor, which efficiently detected H2PO4- in water by a successive 'ON-OFF' fluorescence switching-driven security activity without any exhaustion of the emission phenomenon.