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- Title
OFF-ON-OFF Red-Emitting Fluorescent Indicators for a Narrow pH Window.
- Authors
Cidlina, Antonin; Miletin, Miroslav; Fathi ‐ Rasekh, Mahtab; Nemykin, Victor N.; Zimcik, Petr; Novakova, Veronika
- Abstract
A unique combination of two independent mechanisms of fluorescence quenching, namely intramolecular charge transfer (ICT) from a peripheral donor and protonation of azomethine nitrogen atoms in zinc tetrapyrazinoporphyrazines (TPyzPz), provides a new possibility for sensing pH in a specific range. The pH selectivity was controlled by the different basicities of the donor for ICT (dimethylaminoaryl), which was connected to the macrocycle by π-extended linkers of different lengths. ICT and protonation have been studied in detail by photophysical, spectral (UV/Vis and MCD spectra), and electrochemical measurements, and further supported by theoretical calculations (DFT, TDDFT). The pH-sensing properties of the TPyzPzs have been investigated in THF and in water after anchoring the TPyzPzs to liposomes. The salient p Ka values were around 1.3 (azomethine nitrogen) and 2.29-4.76 (donor for ICT). The lead indicators (sensing over a pH range of 1.0-2.5) with fairly steep sensing profiles exhibited increases in fluorescence between the OFF/ON states of more than 20-fold and strong absorption in the red region (Q-band maximum >650 nm, ϵ≈2×106 m−1 cm−1).
- Subjects
FLUORESCENCE quenching; INTRAMOLECULAR charge transfer; HETEROCYCLIC compounds spectra; MACROCYCLIC compounds; FLUORESCENT probes; SCHIFF bases
- Publication
Chemistry - A European Journal, 2017, Vol 23, Issue 8, p1795
- ISSN
0947-6539
- Publication type
Article
- DOI
10.1002/chem.201604978