Electrochemistry of 9,9'-bifluorenylidene : detection of the radical species by spectroelectrochemical and EPR methods
TL;DR: In this article, it was shown by cyclic voltammetry and differential pulse polarography that 9,9′-bifluorenylidene (BFD) undergoes two successive reduction waves in ap a reversible (E1 = −1.10 V SCE) followed by a quasi-reversible (E2 = − 1.50 V S CE) couple.
About: This article is published in Journal of Electroanalytical Chemistry.The article was published on 1992-03-23. It has received 7 citations till now. The article focuses on the topics: Unpaired electron.
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TL;DR: The inherent potential of a new generation of acceptor compounds based on the 9,9’-bifluorenylidene (99’BF) backbone is reported, and a low overall efficiency, which arises from loss mechanisms, was observed.
Abstract: The tangible possibility of fabricating flexible, lightweight organic photovoltaic devices (OPVs) by using roll-to-roll coaters, similar to those used in the production of print magazines and newspapers, renders this technology a valid alternative to expensive crystalline silicon photovoltaic cells. The most widely used active layer for these OPVs, the so-called bulk heterojunction (BHJ), 5] is based on photoinduced charge transfer from an electron-donating material, such as a light-absorbing and hole-conducting polymer, to an electron-accepting component, typically fullerene[60] and its derivative 1-(3-methoxycarbonyl) propyl-1phenyl-[6,6]-C61 ([C60]PCBM). [6, 7] Several research groups have reported a wide range of new polymeric donor structures that absorb light over a broad wavelength range, and have a narrow energy gap and increased charge transport and collection at the electrode. However, there have been fewer reports on new structures of acceptor components that do not contain fullerene derivatives. C60 and C70 PCBMs are currently considered the most successful acceptor architectures, despite only slight improvements when modifying these functionalized fullerenes. For example, the insertion of electron-donating groups on the phenyl ring of the [C60]PCBM to tune the lowest unoccupied molecular orbital (LUMO) energy levels improved the open-circuit voltage (Voc), while maintaining a relatively unchanged efficiency. Furthermore, [C70]PCBM, which absorbs a wider range of wavelengths than [C60]PCBM, [16] was employed with low-band-gap polymers such as poly[2,6-(4,4-bis-(2-ethylhexyl-4H-cyclopenta[2,1b;3,4b’]-dithiophene)-alt-4,7-(2,1,3-benzothiadizole)] (PCPDTBT), to broaden the photocurrent spectral range. Although encouraging photocurrent and photovoltage values were obtained, a low overall efficiency, which arises from loss mechanisms, was observed. Despite the wide use of these fullerene derivatives, the synthesis of new acceptors with energy levels significantly different from those of current C60 derivatives, and wide versatility in terms of derivatization and functionalization is urgently required. Herein, we report the inherent potential of a new generation of acceptor compounds based on the 9,9’-bifluorenylidene (99’BF) backbone. 99’BF could be considered a tetrabenzofulvalene with an atom numbering that reflects fluorene linked by a double bond between the 9 and 9’ carbon atoms. In the ground state, 99’BF is forced to be coplanar because of the presence of the double bond, but the repulsive interaction between the H1– H1’ and H8–H8’ protons twists the structure of the dimer. The addition of one electron across the C9–C9’ bond is highly favorable for two main reasons: steric (“twist”) strain relief and gain in aromaticity to a 14-p-electron system (Scheme 1).
269 citations
TL;DR: A novel twisted monomer based on a distorted CC double bond for low bandgap conjugated copolymers that exhibits broad absorption spanning both visible and near-infrared regions leading to promising solar cell performance.
Abstract: Here we report a novel twisted monomer based on a distorted CC double bond for low bandgap conjugated copolymers This new building block provides several unique characteristics when compared to classical planar systems such as high solubility, electron accepting ability, and isomeric tunability The resulting copolymers exhibit broad absorption spanning both visible and near-infrared regions leading to promising solar cell performance
41 citations
TL;DR: Two subvalent, redox-active diborane(4) anions, carrying exceptionally high negative charge densities are reported: reduction of 9-methoxy-9-borafluorene with Li granules without stirring leads to the crystallization of the B(sp3 )-B(sp2 ) DIBORANE(5) anion salt Li[5] as discussed by the authors.
Abstract: Two subvalent, redox-active diborane(4) anions, [3]4- and [3]2- , carrying exceptionally high negative charge densities are reported: Reduction of 9-methoxy-9-borafluorene with Li granules without stirring leads to the crystallization of the B(sp3 )-B(sp2 ) diborane(5) anion salt Li[5]. [5]- contains a 2,2'-biphenyldiyl-bridged B-B core, a chelating 2,2'-biphenyldiyl moiety, and a MeO substituent. Reduction of Li[5] with Na metal gives the Na+ salt of the tetraanion [3]4- in which two doubly reduced 9-borafluorenyl fragments are linked via a B-B single bond. Comproportionation of Li[5] and Na4 [3] quantitatively furnishes the diborane(4) dianion salt Na2 [3], the doubly boron-doped congener of 9,9'-bis(fluorenylidene). Under acid catalysis, Na2 [3] undergoes a formal Stone-Wales rearrangement to yield a dibenzo[g,p]chrysene derivative with B=B core. Na2 [3] shows boron-centered nucleophilicity toward n-butyl chloride. Na4 [3] produces bright blue chemiluminescence when exposed to air.
15 citations
TL;DR: In this paper, the anodic oxidation of the title fluorenylidenes in CH2Cl2 + 0.2 M Bu4NBF4 is described and the electrochemical behaviour and physicochemical properties of the derived polymers are discussed and compared with those of other polymethylenefluorenes.
13 citations
TL;DR: In this article, the electroreduction mechanism of vicinal hydroxyl derivatives using 9H,9'H-bifluorene-9, 9'-diol was investigated.
6 citations
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398 citations
TL;DR: In this article, the use of the OTTLE for determining formal redox potentials, n values, and spectra of redox couples is illustrated by measurements on solutions of ferricyanide and o-tolidine.
Abstract: In this experiment, the use of the OTTLE for determining formal redox potentials, n values, and spectra of redox couples is illustrated by measurements on solutions of ferricyanide and o-tolidine u...
156 citations
TL;DR: In this paper, a starting point is provided by molecular structures in which from the outset there is only a very small energy difference between the lowest energy states; such diradicaloid molecules occupy a special position among the various types of organic compounds.
Abstract: Until now the study of organic compounds in which the π-electron system is excited by absorbed light has been mainly concentrated on the ultraviolet and visible regions of the electromagnetic spectrum. Various new applications, such as the use of conjugated organic compounds as dye lasers or as materitals for storing information with the help of diode lasers, led to the synthesis of new compounds which absorb light in the near in infrared (NIR). It is possible to use structure-color relationships to predict the properties of such new compounds when they belong to dyestuff classes which have already been studied in detail; in this case the approach involves decreasing the energy difference between the ground state and the first excited state. A less conventional starting point is provided by molecular structures in which from the outset there is only a very small energy difference between the lowest-energy electronic states; such diradicaloid molecules occupy a special position among the various types of organic compounds. It is possible by means of suitable structural modification to stabilize such molecules in a singlet from which absorbs light at very long wavelengths (i.e. at small wave numbers).
124 citations
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