Pyreno[2,1-b]pyrrole and bis(pyreno[2,1-b]pyrrole) as selective chemosensors of fluoride ion: a mechanistic study.

Pyreno[2,1-b]pyrrole and its dimeric derivative display excellent selectivity and sensitivity for detection of fluoride ion, in comparison with chloride, bromide, iodide, acetate, dihydrogen phosphate, hydrogen sulfate, perchlorate, nitrate, and thiocyanate ions. The hydrogen bonding with fluoride ion, both in formation and in subsequent dissociation, provides remarkable colorimetric and fluorescent changes in the visible region that are advantageous for real-time and on-site application. Detailed NMR and dynamic fluorescence spectroscopic analyses establish the associated mechanism.

Ethynyl-linked (pyreno)pyrrole-naphthyridine and aniline-naphthyridine molecules as fluorescent sensors of guanine via multiple hydrogen bondings.

New fluorescent molecular sensors for 9-alkylguanines were constructed by conjugation of 2-acetamido-1,8-naphthyridine with N-Boc-pyrrole, N-Boc-pyreno[2,1-b]pyrrole, or acetanilide moieties via an ethynyl bridge. In combination with the triple hydrogen-bonding motif of 2-acetamidonaphthyridine toward alkylguanine, an additional binding site was provided by the substituent properly located on the pyrrole or aniline ring to enhance the affinity of these receptor molecules. Besides the ESI-MS analyses, the binding events were readily monitored by the absorption and fluorescence changes in the visible region.

Highly fluorescent pyreno[2,1-b]pyrroles: first syntheses, crystal structure, and intriguing photophysical properties.

A series of pyrrole analogues of benzo[a]pyrene have been synthesized in which pyreno[2,1-b]pyrrole exhibits highly fluorescent properties in solution as well as in crystalline form even possessing strong pi-pi stacking. The pi-stacking-induced fluorescence spectral changes lead to future applications such as molecular recognition feasible upon chemical modification.

Fluorescent and circular dichroic detection of monosaccharides by molecular sensors: bis[(pyrrolyl)ethynyl]naphthyridine and bis[(indolyl)ethynyl]naphthyridine.

The push-pull conjugated molecules 2,7-bis-(1H-pyrrol-2-yl)ethynyl-1,8-naphthyridine (BPN) and 2,7-bis(1H-indol-2-yl)ethynyl-1,8-naphthyridine (BIN) adopting daad relays of proton donors (d) and acceptors (a) form multiple hydrogen-bonding complexes with various monosaccharides that possess complementary adda sequences. Although the free BPN emits blue light at lambda(max) = 475 nm in CH(2)Cl(2), its complexation with octyl beta-d-glucopyranoside gives green fluorescence at lambda(max) = 535 nm. The excellent photophysical properties make BPN a highly sensitive probe for monitoring glucopyranoside to a detection limit of approximately 100 pM. On the other hand, the CD-silent BIN molecule binds with monosaccharides to form the CD-active multiple hydrogen-bonding complexes, which exhibit the remarkable chirality dependent helicities consistent with the prediction by the ab initio approaches. On the basis of the similar daad cleft and hence the binding property, the fluorescence and CD absorption methods in BPN and BIN, respectively, are complementary, which, in combination with computational molecular modeling, not only give a detailed insight into the structures of the receptor-saccharide complexes in solution, but also differentiate octyl beta-d-glucopyranoside from its enantiomer and other monosaccharides.