A concentration dependent auto-relay-recognition by the same analyte: a dual fluorescence switch-on by hydrogen sulfide via Michael addition followed by reduction and staining for bio-activity.

H2S is shown, for the first time, to play an extraordinary dual role due to its nucleophilicity and reducing property with our single chemosensor, PND [4-(piperidin-1-yl) naphthalene-1,2-dione]. The initial nucleophilic attack via Michael addition (a lower concentration of H2S, blue fluorescence) is followed by the reduction of the 1,2-diketo functionality (a higher concentration of H2S, green fluorescence). This chemosensor, which also shows biological response, is remarkably effective in sensing the same analyte (H2S) at its different concentrations in a relay pathway via a fluorescence "off-on-on" mechanism, and this is also supported by DFT calculation and Cyclic voltammograms.

An azodye-rhodamine-based fluorescent and colorimetric probe specific for the detection of Pd(2+) in aqueous ethanolic solution: synthesis, XRD characterization, computational studies and imaging in live cells.

Azodye-rhodamine hybrid colorimetric fluorescent probe (L) has been designed and synthesized. The structure of L has been established based on single crystal XRD. It has been shown to act as a selective turn-on fluorescent chemosensor for Pd(2+) with >40 fold enhancement by exhibiting red emission among the other 27 cations studied in aqueous ethanol. The coordination features of the species of recognition have been computationally evaluated by DFT methods and found to have a distorted tetrahedral Pd(2+) center in the binding core. The probe (L) has been shown to detect Pd up to 0.45 µM at pH 7.4. Furthermore, the probe can be used to image Pd(2+) in living cells.

Cd(2+) Triggered the FRET "ON": A New Molecular Switch for the Ratiometric Detection of Cd(2+) with Live-Cell Imaging and Bound X-ray Structure.

On the basis of the Förster resonance energy transfer mechanism between rhodamine and quinoline-benzothiazole conjugated dyad, a new colorimetric as well as fluorescence ratiometric probe was synthesized for the selective detection of Cd(2+). The complex formation of the probe with Cd(2+) was confirmed through Cd(2+)-bound single-crystal structure. Capability of the probe as imaging agent to detect the cellular uptake of Cd(2+) was demonstrated here using living RAW cells.

Rapid detection of hydrazine in a naphthol-fused chromenyl loop and its effectiveness in human lung cancer cells: tuning remarkable selectivity via the reaction altered pathway supported by theoretical studies.

Our designed and synthesized chemosensor naphthalene based chromenyl derivative (NAC) [1-(3-hydroxy-3 methyl-3H-benzo[f]chromen-2-yl) ethanone] has been used for fast (<30 s, DL = 0.22 ppb) and selective detection of N2H4 by a new way via the chromenyl ring opening followed by the pyrazole ring formation giving a strong blue fluorescence. The DFT study and the real application in different water samples along with the dipstick method in low cost devices have also been performed here. Human lung cancer cells (NCI-H460) have been used for hydrazinolysis of the NAC in vivo system for detection by the appearance of blue fluorescence and also for the MTT assay showing its remarkable cancer sensitivity.

Nanomolar detection of hypochlorite by a rhodamine-based chiral hydrazide in absolute aqueous media: application in tap water analysis with live-cell imaging.

By employing the oxidation property of hypochlorite (OCl(-)), a novel rhodamine-based hydrazide of the chiral acid ((S)-(-)-2-pyrrolidone-5-carboxylic acid) (RHHP) was designed and synthesized for detection of OCl(-) absolutely in aqueous medium at nanomolar level. The structure of the chiral sensor was also proved by the X-ray crystallography. The bioactivity and the application of the probe for detection of OCl(-) in natural water system have been demonstrated. A plausible mechanism for oxidation of the sensor followed by hydrolysis is also proposed. The sensibility of the receptor toward OCl(-) was studied in absolute aqueous media, and the detection limit of hypochlorite-mediated oxidation to the receptor in nanomolar level makes this platform (RHHP) an ultrasensitive and unique system for OCl(-) oxidation.

A new pyrene based highly sensitive fluorescence probe for copper(II) and fluoride with living cell application.

A new pyrene based fluorescence probe has been synthesized for fluorogenic detection of Cu(2+) in acetonitrile-aqueous media (7 : 3 CH3CN-HEPES buffer, v/v, at pH 7.5) with bioimaging in both prokaryotic (Candida albicans cells) and eukaryotic (Tecoma stans pollen cells) living cells. The anion recognition properties of the sensor have also been studied in acetonitrile by fluorescence methods which show remarkable sensitivity toward fluoride over other anions examined.

A highly selective and sensitive probe for colorimetric and fluorogenic detection of Cd2+ in aqueous media.

A new rhodamine-quinoline based dyad has been synthesized. It shows a highly selective response to Cd(2+) in the presence of other competing metal ions in aqueous media (pH = 7.1). The detection limit of the sensor is in the 10(-7) M level.

Ratiometric and absolute water-soluble fluorescent tripodal zinc sensor and its application in killing human lung cancer cells.

A new "naked-eye" and ratiometric fluorescent zinc sensor (TAQ) of carboxamidoquinoline with 2-chloro-N-(quinol-8-yl)-acetamide as a receptor was designed and synthesized. The sensor shows good water solubility and high selectivity for sensing; about a 15-fold increase in fluorescence quantum yield and a 100 nm red-shift of fluorescence emission upon binding Zn²âº in aqueous HEPES buffer solution are observed. The human lung cancer cell line (A549) activity is also demonstrated.

Ethyl 2-[(2-oxo-2H-chromen-7-yl)-oxy]acetate.

In the title compound, C13H12O5, the mean plane of the 2H-chromene ring system (r.m.s deviation = 0.026 Å) forms a dihedral angle of 81.71 (6)° with the mean plane of ethyl 2-hy-droxy-acetate moiety (r.m.s deviation = 0.034 Å). In the crystal, C-H⋯O hydrogen bonds result in the formation of zigzag layers parallel to the bc plane.

7-Hy-droxy-methyl-2-pivaloyl-amino-1,8-naphthyridine.

In the title compound, C14H17N3O2, the mean plane of the 1,8-naphthyridine ring system (r.m.s deviation = 0.020 Å) forms a dihedral angle of 23.4 (1)° with the acetamide moiety (r.m.s deviation = 0.001 Å). The mol-ecular structure is stabilized by an intra-molecular O-H⋯N hydrogen bond, which generates an S(5) ring motif. In the crystal, mol-ecules are linked into inversion dimers by pairs of N-H⋯O hydrogen bonds, generating 18-membered R 2 (2)(18) ring motifs.

Bis(2,1,3-benzoselenadiazole-κN)dibromidocopper(II).

In the title complex, [CuBr(2)(C(6)H(4)N(2)Se)(2)], the Cu(II) ion is tetra-coordinated by two bromide anions and two N atoms in a distorted square-planar geometry. The two essentially planar 2,1,3-benzoselenadiazole ligands [maximum deviations = 0.012 (2) and 0.030 (2) Å] are approximately coplanar [dihedral angle = 6.14 (6)°]. In the crystal, short inter-molecular Se⋯Br, Se⋯N and N⋯N inter-actions are observed. These short inter-actions and inter-molecular C-H⋯Br hydrogen bonds link the complex mol-ecules into two-dimensional arrays parallel to the ac plane.

(Z)-1,2-Dichloro-1,2-bis-(3-chloro-quinoxalin-2-yl)ethene.

The title compound, C(18)H(8)Cl(4)N(4), exists in a cis configuration with respect to the bridging C=C bond. The two essentially planar quinoxaline ring systems [maximum deviations = 0.012 (1) and 0.022 (1) Å] are inclined at an angle of 59.84 (3). In the crystal, adjacent mol-ecules are linked into chains propagating along [001] via inter-molecular C-H⋯N hydrogen bonds. Weak inter-molecular π-π [centroid-centroid distance = 3.6029 (7)°] and C-H⋯π inter-actions are also observed.

Adeninium perchlorate.

IN THE TITLE SALT (SYSTEMATIC NAME: 6-amino-9H-purin-1-ium perchlorate), C(5)H(6)N(5) (+)·ClO(4) (-), the adeninium cation is essentially planar, with a maximum deviation of 0.038 (1) Å. The whole of the perchlorate anion is disordered over two sets of sites with an occupancy ratio of 0.589 (13):0.411 (13). In the crystal, the adeninium cations are linked by pairs of N-H⋯N hydrogen bond into inversion dimers. The dimers and the anions are further inter-connected into a three-dimensional supra-molecular structure via inter-molecular N-H⋯O, C-H⋯O and C-H⋯N hydrogen bonds.

Ethyl 7-pivaloyl-amino-1,8-naphthyridine-2-carboxyl-ate sesquihydrate.

In the title hydrate, C(16)H(19)N(3)O(3)·1.5H(2)O, both water mol-ecules are disordered: one over two adjacent sites in a 0.498 (5):0.502 (5) ratio and one lying near a crystallographic twofold axis. The dihedral angle between the pyridine rings of the organic moleucle is 1.47 (6)°. In the crystal, the components are linked by N-H⋯O, O-H⋯N and C-H⋯O hydrogen bonds, forming sheets lying parallel to the ac plane.

N-Benzyl-4-methyl-6-phenyl-pyrimidin-2-amine.

In the title compound, C(18)H(17)N(3), the dihedral angles between the central pyrimidine ring and its directly-bonded and N-bonded pendant phenyl rings are 25.48 (6) and 80.33 (6)°, respectively. The dihedral angle between the phenyl rings is 79.66 (6)°. In the crystal, inversion dimers linked by pairs of N-H⋯N hydrogen bonds generate R(2) (2)(8) loops. The crystal structure also features weak π-π [centroid-centroid separation = 3.6720 (7) Å] and C-H⋯π inter-actions.

N-Butyl-4,6-diphenyl-pyrimidin-2-amine.

In the title compound, C(20)H(21)N(3), the pyrimidine ring is inclined at dihedral angles of 51.57 (4) and 2.49 (4)° to the two phenyl rings. The dihedral angle between the two terminal phenyl rings is 50.44 (4)°. In the crystal, adjacent mol-ecules are linked via a pair of N-H⋯N hydrogen bonds, forming an inversion dimer with an R(2) (2)(8) ring motif. Furthermore, the crystal structure is stabilized by a weak π-π inter-action, with a centroid-centroid distance of 3.6065 (5) Å.

Methyl pyrido[2,3-b]pyrazine-3-carboxyl-ate.

The asymmetric unit of the title compound, C(9)H(7)N(3)O(2), is composed of two independent mol-ecules. The crystal structure is stabilized by C-H⋯O and C-H⋯N hydrogen bonds, forming a three-dimensional network. The crystal structure also features pyrazine-pyrazine π-π inter-actions [centroid-centroid distance = 3.6994 (5) Å] and also pyridine-pyrazine π-π inter-actions [centroid-centroid distance = 3.6374 (5) Å].

Guanidinium chloro-chromate.

In the title compound, guanidinium chloridotrioxidochrom-ate(VI), (CH(6)N(3))[CrClO(3)], both the cation and anion are generated by crystallographic mirror symmetry, with one O and one N atom and the Cr, Cl and C atoms lying on the mirror plane. The bond lengths in the guanidinium cation are inter-mediate between normal C-N and C=N bond lengths, indicating significant delocalization in this species. In the crystal structure, inter-molecular N-H⋯Cl inter-actions generate R(2) (1)(6) ring motifs. These ring motifs are further inter-connected by inter-molecular N-H⋯O hydrogen bonds into infinite chains along [010].

2,9-Bis(trichloro-meth-yl)-1,10-phenanthroline.

The asymmetric unit of the title compound, C(14)H(6)Cl(6)N(2), contains two crystallographically independent mol-ecules, each of which is slightly twisted from planarity. The dihedral angles between the central ring and the two outer rings are 3.81 (7) and 4.30 (7)° in one mol-ecule, and 4.13 (8) and 4.10 (7)° in the other. In the crystal structure, mol-ecules are inter-linked by C-Cl⋯Cl inter-actions into sheets parallel to the ac plane. These sheets are stacked along the b axis in such a way that the mol-ecules are anti-parallel; they are further connected into a supra-molecular network. There are no classical hydrogen bonds. C⋯Cl [3.637 (2) Å], Cl⋯Cl [3.5639 (5)-3.6807 (8) Å] and Cl⋯N [3.3802 (15)-3.4093 (15) Å] short contacts and π-π inter-actions, with centroid-centroid distances in the range 3.5868 (9)-3.7844 (9) Å, are observed.

2,7-Bis-(trichloro-meth-yl)-1,8-naphthyridine.

The complete mol-ecule of the title compound, C(10)H(4)Cl(6)N(2), is generated by crystallographic twofold symmetry, with two C atoms lying on the rotation axis; the 1,8-naphthyridine ring is almost planar with an r.m.s. deviation of 0.0002 Å. In the crystal structure, the mol-ecules are stacked in an anti-parallel manner along [001]. Short Cl⋯Cl [3.3502 (4)] and Cl⋯N [3.2004 (11)-3.2220 (10) Å] contacts are observed in the crystal structure.