Circularly polarized luminescence of natural products lycorine and narciclasine: role of excited-state intramolecular proton-transfer and test of pH sensitivity

Year: 2023

Authors: Mazzeo G., Fusi M., Evidente A., Abbate S., Longhi G.

Autors Affiliation: Univ Brescia, Dept Mol & Translat Med, Viale Europa 11, I-25123 Brescia, Italy; Univ Napoli Federico II, Dept Chem Sci, Via Cintia 21, I-80126 Naples, Italy; CNR, Inst Sci Food Prod, Via Amendola 122-O, I-70185 Bari, Italy; CNR, Natl Inst Opt, Brescia Res Unit, Via Branze 45, I-25123 Brescia, Italy.

Abstract: Circularly polarized luminescence (CPL) is increasingly gaining interest not only for its applicative potentialities but also for providing an understanding of the excited state properties of chiral molecules. However, applications of CPL are mainly in the field of materials science: special organic molecules and polymers, metal (lanthanide) complexes, and organic dyes are actively and intensely studied. So far natural compounds have not been investigated much. We fill the gap here by measuring circular dichroism (CD) and CPL of lycorine and narciclasine, the most abundant known alkaloid and isocarbostyril from Amaryllidaceae, which exhibit a large spectrum of biological activities and are promising anticancer compounds. Dual fluorescence detection in narciclasine led us to unveil an occurring excited-state intramolecular proton transfer (ESIPT) process, this mechanism well accounts for the Stokes shift and CPL spectra observed in narciclasine. The same molecule is interesting also as a pH chiroptical switch. Both in absorption and emission, lycorine and narciclasine are also studied computationally via density functional theory (DFT) calculations further shedding light on their properties.

Journal/Review: PHYSICAL CHEMISTRY CHEMICAL PHYSICS

More Information: The Italian Ministry of University and Research (PRIN 2017 program 2017A4XRCA_003) is acknowledged for funding. The Big & Open Data Innovation Laboratory (BODaILab) of the University of Brescia and Computing Center CINECA (Bologna, Italy), awarded under the ISCRA initiative, are acknowledged for providing high-performance computing facilities.
KeyWords: Absolute-configuration; Spectra; Dichroism; Fluorescence; Derivatives; Artifacts; Emission; Growth
DOI: 10.1039/d3cp02600k

Citations: 4
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