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

Abstract

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.

1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research

“…Furthermore, noticeable bathochromic shifts of the fluorescence bands were observed for M 2 Zn 2+ and M 2 Mg 2+ complexes. These findings were explained by the formation of excimer species [M 2+ (MM)]*, which was confirmed by quantum chemical calculations [177]. In 2013, the same research group demonstrated a detailed study on the pyrazoloquinoline derivative PQ 1d, which was a direct precursor for the synthesis of the aza-crown fluorescence probe PQ 1, previously reported by Rurack [5].…”

“…It was found that this compound can act as a highly efficient Since the aforementioned studies on pyrazoloquinoline-based sensors were reported, almost a decade passed until this stem was followed. Then, between 2010 and 2013, Mac and co-workers published a series of articles on ion-sensitive pyrazoloquinolines, which varied by the molecular architecture of the receptor unit (see Figure 16b) [175][176][177]. All of the sensors presented (PQ 1a-d) were designed for PET signalling, and they maintained the connection between the receptor unit and the pyrazoloquinoline chromophore via the non-conjugated methylene spacer.…”

A novel fluorescent probe with a pyrazolo[4,3-c]quinoline core selectively recognizes c-MYC promoter G-quadruplexes

“…Generally, an ideal G-quadruplex fluorescent probe is assumed to consist of a fluorescent signaling unit specifically recognizing the G-quadruplex structure. Pyrazoloquinolines have been shown to be efficient organic emitters, [16][17][18] with applications in fluorescence sensing 19,20 and electroluminescence. 21 Recently, a derivative of this class of compounds showed a selective binding to human telomeric G4 multimers over monomeric ones.…”

Blue‐Fluorescent Probes for Lipid Droplets Based on Dihydrochromeno‐Fused Pyrazolo‐ and Pyrrolopyridines

“…An interesting blue-fluorescent marker for LDs is the commercially available monodansylpentane (MDH), which has been successfully used in multicolor live cell imaging, supporting the importance of the discovery of new markers emitting in this region of the visible spectra. This was not surprising because the pyrazolo skeleton can be found as a subunit together with other moieties such as pyridine, [9] coumarin, [10] quinoline, [11][12][13] and quinoxaline [14] in tri-and tetracyclic molecules that show fluorescent properties. This was not surprising because the pyrazolo skeleton can be found as a subunit together with other moieties such as pyridine, [9] coumarin, [10] quinoline, [11][12][13] and quinoxaline [14] in tri-and tetracyclic molecules that show fluorescent properties.…”