A New Fluorescent Sensor Based on 1H-pyrazolo[3,4-b]quinoline Skeleton. Part 2

A novel fluorescent dye bis-(pyridin-2-yl-methyl)-(1,3,4-triphenyl-1H-pyrazolo[3,4-b]quinolin-6-ylmethyl)-amine (P1) has been synthesized and investigated by means of steady state and time-resolved fluorescence techniques. This compound acts as sensor for fluorescence detection of small inorganic cations (lithium, sodium, barium, magnesium, calcium, and zinc) in highly polar solvents such as acetonitrile. The mechanism which allows application of this compound as sensor is an electron transfer from the electron-donative part of molecule (amine) to the acceptor part (pyrazoloquinoline derivative), which is retarded upon complexation of the electro-donative part by inorganic cations. The binding constants are strongly dependent on the charge density of the analyzed cations. The 2/1 complexes of P1 with Zn++ and Mg++ cations posses large binding constants. Moreover, in the presence of these cations a significant bathochromic shift of fluorescence is observed. The most probable explanation of such behaviour is the formation of intramolecular excimer. This is partially supported by the quantum chemical calculations

A new calix [4] arene-based fluorescent sensor for sodium ion

A new calix[4]arene with three ester groups and an appended naphthalenic fluorophore has been synthesized; investigation of its photophysical and complexing properties towards alkali and alkaline-earth metal ions reveals a high selectivity for Na+ in water–ethanol mixtures

Ion-responsive fluorescent compounds VI. Coumarin 153 linked to rigid crowns for improvement of selectivity

The photophysical and complexing properties of fluoroionophores consisting of the coumarin C153 linked to dibenzo-16-crown-5 (C153-DBC) and tribenzo-19-crown-6 (C153-TBC) are described in acetonitrile and ethanol. The carbonyl group of the coumarin moiety is in direct interaction with a bound cation. The selectivity of these compounds for a given alkali or alkaline earth metal ion was found to be better than that of previously reported crowned coumarins owing to the rigidity of dibenzo- and tribenzocrowns. In acetonitrile, a very high selectivity for Ca2+ versus Mg2+ has been found. In ethanol, C153-DBC is selective for Na+ and C153-TBC is selective for K+, as expected from the relative size of the crown cavity. (C) 2000 Elsevier Science S.A. All rights reserved