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Abstract  Two new binaphthyl derivatives 1 and 2 bearing two imidazolium, or bisurea groups were investigated as fluorescent chemosensors for the chiral anion recognition. Receptors 1 and 2 displayed a better selectivity for (S)-2-phenylbutylate over (R)-2-phenylbutylate. Isothermal titration calorimeter methods, fluorescence as well as theoretical calculations are utilized to explain chiral selectivity. Graphical Abstract   [ABSTRACT FROM AUTHOR]

Paper based on a presentation at the 18th IUPAC International Conference on Physical Organic Chemistry (ICPOC-18), 20-25 August 2006, Warsaw, Poland. Other presentations are published in this issue, pp. 955-1151.For the design of functional molecules and nanodevices, it is very useful to utilize nanorecognition (which is governed mainly by interaction forces such as hydrogen bonding, ionic interaction, π-H/π-π interactions, and metallic interactions) and nanodynamics (involving capture, transport, and release of electrons, photons, or protons). The manifestation of these interaction forces has led us to the design and realization of diverse ionophores/receptors, organic nanotubes, nanowires, molecular mechanical devices, molecular switches, enzyme mimetics, protein folding/unfolding, etc. In this review, we begin with a brief discussion of the interaction forces, followed by some of our representative applications. We discuss ionophores with chemo-sensing capability for biologically important cations and anions and explain how the understanding of hydrogen bonding and π-interactions has led to the design of self-assembled nanotubes from calix[4]hydroquinone (CHQ). The binding study of neutral and cationic transition metals with the redox system of hydroquinone (HQ) and quinone (Q) predicts what kind of nanostructures would form. Finally, we look into the conformational changes between stacked and edge-to-face conformers in π-benzoquinone-benzene complexes controlled by alternating electrochemical potential. The resulting flapping motion illustrates a promising pathway toward the design of mobile nanomechanical devices. [ABSTRACT FROM AUTHOR]

Quinoxaline derivatives (1−4) bearing two imidazolium moieties are found to strongly bind anions and show unique charge-transfer fluorescent responses to pyrophosphate and acetate, whereas they show excimer formation with other anions. Anion-binding studies are investigated with fluorescence and 1H NMR analysis, single-crystal X-ray analysis, and theoretical calculations. [ABSTRACT FROM AUTHOR]

Function of nicotine, which induces activation of all parts of the body including our brain, has been receiving much attention for a long period of time and also been actively studied by researchers for its pharmacological actions in the central nervous system. The modulation of nicotine concentration and the inhibition of nicotine binding on target receptors in the brain are the key factors for smoking addiction therapy. In previous studies showed that influx of nicotine at the blood-brain barrier was through the pyrilamine-sensitive organic cation transporters. But the direct interacting mechanism of pyrilamine on the nicotine binding target receptors has not yet been clarified. The aim of the present study is to investigate the direct binding mechanisms of a pyrilamine on the nicotinic acetylcholine receptors (nAChRs). We found that pyrilamine shares the same ligand binding pocket of nicotine (NCT) on nAChRs but interacts with more amino acid residues than NCT does. The extended part of pyrilamine interacts with additional residues in the ligand binding pocket of nAChRs which are located nearby the entrance of the binding pocket. The catecholamine (CA) secretion induced by nAChR agonist (NCT') was significantly inhibited by the pyrilamine pretreatment. Real time carbon-fiber amperometry confirmed the inhibition of the NCT'-induced exocytosis by pyrilamine in a single cell level. We also found that pyrilamine inhibited the NCT'-induced [Ca(2+)]i. In contrast, pyrilamine did not affect the increase in calcium induced by high K(+). Overall, these data suggest that pyrilamine directly docks into the ligand binding site of nAChRs and specifically inhibits the nAChR-mediated effects thereby causing inhibition of CA secretion. Therefore, pyrilamine may play an important role to explore new treatments to aid smoking cessation., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

Interaction between positively charged aromatic groups (π(+)-π(+)) is characterized by anti-parallel, displaced-stacked structures in the presence of counteranions. Binding energies of pyridinium, N-methylpyridinium and N-methylimidazolium dimers are much larger than that of benzene-pyridine (π-π) and pyridinium-benzene (π(+)-π). Stabilization is attributed to attractive electrostatic interaction with significant dispersion contribution., (This journal is © the Owner Societies 2011)