Photophysical properties of 1-pyridine-3-phenylpyrazoloquinoline and molecular logic gate implementation
Tomasz Uchacz , Paweł Szlachcic , Andrzej Danel , Mercedes Kukułka , Monika Srebro-Hooper , Grzegorz Stopa , Katarzyna M. Stadnicka
AbstractThe work demonstrates the photophysical properties of 1-(2-pyridyl)-3-phenyl-pyrazolo[3,4-b]quinoline with the focus on the effect of pyridyl substituent on excited-state deactivation of the pyrazoloquinoline core, and on the molecular logic gate implementation. The deactivation mechanism of the singlet excited state was investigated by means of UV-vis absorption, steady-state and time-resolved fluorescence spectroscopy as well as nanosecond laser flash photolysis. The maximum of absorption (emission) in nonpolar cyclohexane is located at 385 nm (421 nm) and only slightly depends on solvent polarity. The compound exhibits a moderate fluorescence (up to 42%) and a low-temperature phosphorescence (77 K). The studies reveal that the pyridyl group modifies the deactivation mechanism by triggering efficient intersystem crossing. Moreover, the effect of various chemical species: proton, electron-donating amine, and dihydrogenphosphate anion on the absorption and emission of the investigated dye was evaluated. The interpretation of the fluorescence behaviour in the presence or absence of the chemical inputs leads to the realization of unimolecular logic circuits that are able to perform advanced arithmetic operations, such as subtraction (XOR/INH) or IMP/INH logic circuit. The experimental results were supported by quantum-chemical calculations.
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