Hole transfer equilibrium in rigidly linked bichromophoric molecules

Two bichromophoric molecules consisting of anthracene and diphenylpolyene moieties linked by two fused norbornyl bridges undergo photoionization upon ultraviolet (UV) pulsed laser irradiation. The simultaneous observation of the cation radicals of both anthracene and polyene groups points to a rapid (nanosecond or faster) intramolecular hole transfer equilibrium between the two chromophores. The existence of an equilibrium is supported by the results of one- and two-laser transient absorption and electrochemical experiments. Equilibrium constants (293 K) were determined by both transient absorption and cyclic voltammetry measurements and were independent of the method used within experimental error. For A-sp-VB, which contains anthracene and vinyldiphenylbutadiene chromophores, Keq = 4.0 ? 2 (transient absorption) and 3.2 ? 2 (electrochemical), favoring the anthracene cation radical. For A-sp-VS, containing anthracene and vinylstilbene groups, Keq = 70 ? 30 (transient absorption) and 105 ? 50 (electrochemical), favoring the anthracene cation radical.Peer reviewed: YesNRC publication: Ye

Graphitic Mesoporous Carbons with Embedded Prussian Blue-Derived Iron Oxide Nanoparticles Synthesized by Soft Templating and Low-Temperature Graphitization

A series of highly graphitized mesoporous carbons was synthesized by self-assembly of polymeric carbon precursors and block copolymer template in the presence of poly­(vinylpyrrolidone) (PVP)-coated Prussian blue (PB) nanoparticles used as a graphitization catalyst. Resorcinol and formaldehyde were used as carbon precursors, poly­(ethylene oxide)–poly­(propylene oxide)–poly­(ethylene oxide) triblock copolymer (Pluronic F127) was employed as a soft template. The carbon precursors were polymerized in hydrophilic domains of block copolymer along with PVP-coated PB nanoparticles, followed by carbonization. This recipe gave carbons with cylindrical mesopores created by thermal decomposition of the soft template, and with PB-derived iron oxide nanoparticles. In addition, the presence of iron species catalyzed graphitization at relatively low temperature. The XRD and TEM measurements revealed that the resulting carbons obtained with smaller amounts of PB exhibited ordered mesostructures with relatively high degree of graphitization; however, exceedingly graphitic carbons with disordered mesopores were obtained with higher amounts of PB. Furthermore, wide-angle XRD measurements and TGA analysis provided evidence that graphitization took place at 600 °C, which is considered to be a very low temperature for the graphitization process. N₂ adsorption and TGA analysis showed that the aforementioned carbons exhibited high surface area (reaching 621 m²/g) and an extremely high percentage of graphitic domains (approaching 87%). Interestingly, the carbon prepared with larger amount of PB showed magnetic properties. Electrochemical measurements performed on these carbons for double layer capacitors showed somewhat rectangular shape of cyclic voltammetry (CV) curves with a large capacitance of 211 F/g in 1 M H₂SO₄ electrolyte