In recent years, bipolar organic electrode materials have gained recognition as competitive alternatives to inorganic materials due to their unique multielectron redox mechanism for energy storage. In this study, we examined the mechanism of redox reactions in naphthalimide (NI) derivatives when used as electrodes in lithium half-cells with ionic liquid electrolytes. The NI derivatives consist of three building fragments: an aromatic naphthalene core, N-alkylated imide unit, and a peri-dichalcogenide bridge. The integration of electrochemical and microscopic methods with DFT calculations facilitates the delineation of the role of each fragment in the oxidation and reduction reactions of NI derivatives. It is found that the peri-dichalcogenide bridge is mainly involved in the oxidation of NI derivatives above 3.9 V, the charge compensation being achieved by electrolyte TFSI⁻ counter-ions. The reduction of NI derivatives with two Li⁺ ions is mainly due to the participation of the chalcogenide bridge, while after interaction with the next two Li⁺ ions, the imide fragment and the naphthalene moiety contribute equally to the reduction. Based on the leading role of the peri-dichalcogenide bridge, the redox properties of NI derivatives are effectively controlled by the gradual replacement of S with Se and Te atoms in the bridge. To improve the electronic conductivity of NIs, composites with rGO are also synthesized by a simple procedure of mechanical mixing in a centrifugal mixer. The composites rGO/NIs display a good storage performance, the best being the Se-containing analogue.

This review summarizes the synthesis and structural modification of α-pyrone-containing phloroglucinol derivatives from Helichrysum species. Synthetic routes to both natural products and synthetic analogues are covered, highlighting strategies ranging from β-keto ester cyclodehydration to multicomponent condensations. Key methods include aldehyde-mediated dimerization, fluoride-catalyzed heterodimerization, and acid-catalyzed cyclization to benzopyran frameworks. The reported approaches enabled access to diverse monopyrone, dipyrone, arzanol-type, and cyclized analogues. Additionally, retrosynthetic analyses toward phloroglucinol–pyrone heterodimers are discussed, highlighting convergent synthetic strategies for future access to benzofurane-, chromene-, and chromane-based analogues. This review integrates published experimental data with newly generated in silico predictions.

The objective of this study was to design and evaluate π-extended 1,8-naphthalimide derivatives as photoinduced electron transfer (PET) optical sensors for protons and metal cations, with emphasis on the role of heterocyclic annulation and receptor–chromophore electronic matching. Benzofuran- and benzodioxin-annulated naphthalimides bearing either a dimethylaminoethyl receptor or a non-donating alkyl substituent at the imide nitrogen were synthesized using tailored synthetic strategies. Their photophysical properties were investigated by absorption and fluorescence spectroscopy, while sensing performance was evaluated by fluorescence titrations. Quantum chemistry calculations were employed to rationalize experimental observations. Benzofuran-annulated derivatives exhibit structured π–π* absorption bands and strong fluorescence, whereas introduction of the receptor induces efficient fluorescence quenching via reductive PET. Protonation or metal ion coordination suppresses PET and leads to pronounced fluorescence enhancement, particularly in the presence of Cu(II) and Sn(II). In contrast, benzodioxin-annulated derivatives display intramolecular charge-transfer absorption bands, large Stokes shifts, and low fluorescence quantum yields in polar media, resulting in a negligible sensing response. Computational results attribute this behavior to an unfavorable energy arrangement of the donor–acceptor orbitals. Overall, the study demonstrates that heterocyclic annulation critically governs the electronic structure and sensing performance of naphthalimide fluorophores, providing guidelines for the rational design of PET-based optical sensors.