Covalent Dimers of 1,3-Diphenylisobenzofuran for Singlet Fission: Synthesis and Electrochemistry

Abstract

The synthesis of covalent dimers in which two 1,3-diphenylisobenzofuran units are connected through one phenyl substituent on each is reported. In three of the dimers, the subunits are linked directly, and in three others, they are linked via an alkane chain. A seventh new compound in which two 1,3-diphenylisobenzofuran units share a phenyl substituent is also described. These materials are needed for investigations of the singlet fission process, which promises to increase the efficiency of solar cells. The electrochemical oxidation and reduction of the monomer, two previously known dimers, and the seven new compounds have been examined, and reversible redox potentials have been compared with results obtained from density functional theory. Although the overall agreement is satisfactory, some discrepancies are noted and discussed.

Davydov splitting and singlet fission in excitonically coupled pentacene dimers

“…Substantial efforts have been made to develop molecular systems suitable for efficient SF, and the number of chromophores that fulfill the necessary requirements, although somewhat limited, is currently increasing to include acenes,17–22 diphenylisobenzofurans,23–25 carotenoids,26,27 rylenes,28–30 and others 31–33. With a wider selection of potential SF-chromophores available, the more difficult task of deciphering the mechanistic and morphological details associated with SF must now be addressed.…”

Quintet multiexciton dynamics in singlet fission

“…However, covalently linked SF dimers (Figure 1a) offer significant advantages for detailed mechanistic studies of SF due to their chemical tunability. [21][22][23][24][25][26] Recently, several reports have shown efficient intramolecular SF in isolated acene dimers and demonstrated that modifying their structure can systematically tune the rate of triplet pair generation and decay. [27][28][29][30][31] For example, we have previously employed acene heterodimers, systematically varying the energy of the (TT) states produced by SF, and uncovered an energy gap law which governs non-radiative triplet pair recombination.…”

Liquid Crystallinity as a Self‐Assembly Motif for High‐Efficiency, Solution‐Processed, Solid‐State Singlet Fission Materials

“…SF was first observed in crystalline anthracene, and has been extensively studied in this molecular system . SF has since been reported with high yields in polyacenes, such as tetracene, pentacene and their derivatives, oligophenyls, diphenylisobenzofuran, carotenoids, rylene‐based chromophores, perylenediimides, diketopyrrolopyrroles (DPP) derivatives, and some conjugated polymers . Efficient SF has been reported mainly in condensed matter systems, e.g., crystals, polycrystalline films, amorphous films, nanoparticles and aggregates .…”

“…[4,5] Recent studies show that the correlated triplet pair ( 1 TT) state may convert first to a spatially separated triplet pair intermediate 1 (T…T) before it undergoes dephasing or decorrelation into two independent triplets. [2] SF has since been reported with high yields in polyacenes, [7,8] such as tetracene, pentacene and their derivatives, oligophenyls, [9] diphenylisobenzofuran, [10] carotenoids, [11,12] rylene-based chromophores, [13] perylenediimides, [14] diketopyrrolopyrroles (DPP) derivatives, and some conjugated polymers. [6] For SF the energy of the singlet state (E(S 1 )) should be greater than or equal to twice the energy of the triplet state (E(T 1 )), i.e., E(S 1 ) ≥ 2E(T 1 ).…”