Dicationic N-methylated at pyridyl or quinolyl moieties derivatives of three isomers of N,N'-bis(pyridyl)pyridine-2,6-dicarboxamide (o-, m-, and p-1) and of N,N'-bis(3-quinolyl)pyridine-2,6-dicarboxamide (4) strongly bind anions in MeCN (log K in the range 3.5-6.5) with pronounced selectivity for Cl(-) and also bind neutral urea and amide guests with log K in the range 1.1-2.8. Crystal structures of the triflate salts of m-1, p-1, and 4 show that amide NH and pyridinium o-CH groups are directed inside the receptor cleft with their four protons forming a circle of radius ca. 2.35 A optimal for inclusion of Cl(-). The binding of anions to these protons is evident from the crystal structure of a mixed triflate/chloride salt of p-1, calculated (DFT/B3LYP 6-31G**) structures of 1:1 complexes of all receptors with Cl(-), and results of (1)H NMR titrations. In the crystal structure of o-1 pyridinium N-Me(+) groups are directed inside the receptor cleft impeding the anion complexation, but calculations demonstrate that simple rotation of pyridinium rings in opposite directions by ca. 30 degrees creates a cavity to which the Cl(-) ion can fit forming 4 hydrogen bonds to amide NH and aliphatic CH groups of N-Me(+). The results of (1)H NMR titrations confirm this type of binding in solution. Anions quench the intense fluorescence of 4, which allows their fluorescent sensing in the muM range. A new methodology for determination of anion binding constants to strongly acidic receptors by inhibitory effects of anions on the receptor deprotonation by an external base has been developed. High affinity and selectivity of anion complexation by dicationic pyridine-2,6-dicarboxamides is attributed to the rigid preorganized structure of receptors, the high acidity of NH and CH groups, and the electrostatic charge effect.

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<p align="left"><strong>Background</strong>: <em>Salvia circinata</em> is an endemic species of Mexico used in the folk medicine of Santiago Huauclilla, Oaxaca, mainly as remedy for gastrointestinal diseases.</p><p align="left"><strong>Hypothesis</strong>: If the extracts of <em>Salvia circinata</em> have secondary metabolites with antinociceptive activity, then the behavior of nociception in the model of “whriting” in mice will decrease.</p><p align="left"><strong>Specie studied</strong>:<strong> </strong><em>Salvia circinata </em>Cav. (Lamiaceae).</p><p align="left"><strong>Study site and years of study</strong>: <em>Salvia circinata </em>was collected in Santiago Huauclilla, Oaxaca, in July 2014.</p><p align="left"><strong>Methods</strong>: Firstly, the acute toxicity of <em>S. circinata</em> extracts was evaluated to calculate the LD₅₀with OECD method. Then, dose-response curves of the antinociceptive effect of <em>S. circinata</em> organic and aqueous extracts (1, 10, 30, 100, and 300 mg/kg) were obtained in the writhing test in mice. Furthermore, chromatographic techniques were applied to isolate the compounds and were identified by comparison of the values of ¹H NMR, ¹³C NMR and ESIMS reported in the literature.</p><p align="left"><strong>Results</strong>: Our data showed significant antinociceptive activity in all the tested extracts. Amarisolide A and pedalitin were isolated in the ethyl acetate and methanol extracts, respectively and assayed at doses of 1, 5 and 10 mg/kg, i.p. All the compounds decreased nociception in mice in at least 50 % from a minimal dosage of 1 mg/kg, i.p. and in a similar manner than the reference drug ketorolac (1 mg/kg, i.p.).</p><p align="left"><strong>Conclusions</strong>: Our findings give evidence that <em>Salvia circinata </em>possesses antinociceptive activity depending on the presence of several known bioactive constituents, reinforcing its use in the Mexican traditional medicine to alleviate abdominal pain.</p>

The new luminescent platinum(II) pincer complex [Pt(NCN)(S)]TfO (I; NCN = 1,3-bis(2-Nphenylbenzimidazolyl)benzene, S = solvent, and TfO − = triflate anion) was synthesized and studied as a chemosensor for chloride in aqueous media. In 50 vol % aqueous DMF or CH 3 CN chloride quenches the fluorescence with association constants of 1.2 × 10 3 and 81 M −1 , respectively. On the other hand, in the micellar medium of cetyltrimethylammonium hydrogensulfate at pH 7.0 additions of inorganic anions to I enhance the fluorescence with a pronounced selectivity toward chloride, which shows also much tighter binding to the receptor with association constant 7.9 × 10 4 M −1 in comparison to that in mixed organic solvents. On basis of 1 H NMR titration experiments and the crystal structure of the neutral chloro complex of I the binding mode of chloride is proposed involving the coordination of chloride to the Pt(II) atom with simultaneous formation of intramolecular short C−H•••Cl−Pt contacts. The combination of the cyclometalated platinum complex I with a cationic surfactant allows for the detection of chloride in the micromolar concentration range in samples of bottled mineral water.