Optical Energy Transport and Interactions between the Excitations in a Coumarin−Perylene Bisimide Dendrimer

Recent Advances in Functional Polymers Containing Coumarin Chromophores

Natural and synthetic coumarin derivatives have gained increased attention in the design of functional polymers and polymer networks due to their unique optical, biological, and photochemical properties. This review provides a comprehensive overview over recent developments in macromolecular architecture and mainly covers examples from the literature published from 2004 to 2020. Along with a discussion on coumarin and its photochemical properties, we focus on polymers containing coumarin as a nonreactive moiety as well as polymer systems exploiting the dimerization and/or reversible nature of the [2πs + 2πs] cycloaddition reaction. Coumarin moieties undergo a reversible [2πs + 2πs] cycloaddition reaction upon irradiation with specific wavelengths in the UV region, which is applied to impart intrinsic healability, shape-memory, and reversible properties into polymers. In addition, coumarin chromophores are able to dimerize under the exposure to direct sunlight, which is a promising route for the synthesis and cross-linking of polymer systems under "green" and environment-friendly conditions. Along with the chemistry and design of coumarin functional polymers, we highlight various future application fields of coumarin containing polymers involving tissue engineering, drug delivery systems, soft robotics, or 4D printing applications.

Electrical and structural properties of multi-walled carbon nanotube–doped polymer electrolyte for photo electrochemical device

The present investigation deals with the preparation of multi-walled carbon nanotube (MWCNT)-doped plasticized polymer electrolyte. The nanocomposite has been prepared using solution casting method. Complex impedance spectroscopy study revealed the utmost room temperature conductivity of 5.6 × 10−4 S/cm when optimized plasticized polymer electrolyte (poly(ethyl methacrylate)+30% sodium iodide+60% ethylene carbonate) was doped with 7% MWCNT. Temperature dependence of conductivity showed Arrhenius behavior. The surface morphology and crystalline–amorphous deviation of the composite was observed using scanning electron microscope. Perfect complexation of various components of the composite was confirmed from Fourier-transform infrared spectroscopy and X-ray diffraction (XRD) data. The transference number measurement was done to calculate the proportionate amount of ionic and electronic conductivity. A dye sensitized solar cell has been fabricated using maximum ionic conductivity of solid polymer electrolyte and its electrical parameters measured at 1 sun condition.

Coumarin-Tetrapyrrolic Macrocycle Conjugates: Synthesis and Applications

This review covers the synthesis of coumarin-porphyrin, coumarin-phthalocyanine and coumarin-corrole conjugates and their potential applications. While coumarin-phthalocyanine conjugates were obtained almost exclusively by tetramerization of coumarin-functionalized phthalonitriles, coumarin-porphyrin and coumarin-corrole conjugates were prepared by complementary approaches: (a) direct synthesis of the tetrapyrrolic macrocycle using formylcoumarins and pyrrole or (b) by functionalization of the tetrapyrrolic macrocycle. In the last approach a range of reaction types were used, namely 1,3-dipolar cycloadditions, hetero-Diels-Alder, Sonogashira, alkylation or acylation reactions. This is clearly a more versatile approach, leading to a larger diversity of conjugates and allowing the access to conjugates bearing one to up to 16 coumarin units.

Control of the electronic energy transfer pathway between two single fluorophores by dual pulse excitation

We report on the control of the energy transfer pathway in individual donor-acceptor dyads by proper timing of light pulses matching the donor and acceptor transition frequencies, respectively. Excitation of both chromophores at virtually the same time induces efficient singlet-singlet annihilation, whereby excitation energy effectively flows from the acceptor to the donor. The dual pulse excitation scheme implemented here allows for all-optical switching of the fluorescence intensity at the single-molecule level. The population of higher excited states at the donor site was found to significantly increase the photobleaching probability.