The synthesis, characterization, and photovoltaic performance of a series of N-annulated PDI materials is presented. Four novel N-annulated PDI compounds are reported, each of which can be synthesized in gram scale without the need for purification using column chromatography. N-Annulation of the PDI chromophore results in a decrease in electron affinity and lowering of the ionization potential, and renders the chromophore insoluble in organic solvents. Installation of an alkyl group improves the solubility. Single crystal X-ray analysis reveals a bowing of the aromatic backbone and compression of phenyl rings adjacent to the N atom. A brominated N-annulated PDI derivate represents a valuable synthon for creating novel multi-PDI chromophore materials. To demonstrate the utility of the new synthon for making electron transporting materials, a dimerization strategy was employed to create a dimeric PDI material. The PDI dimer has excellent solubility and film forming ability along with energetically deep HOMO and LUMO energy levels. X-ray crystal structure analysis reveals that, despite the isotropic nature of the molecule, only 1-D charge transport pathways are formed. Solar cells based on the new PDI dimer with the standard donor polymer PTB7 gave a high power conversion efficiency of 2.21% for this system. Through N-alkyl chain modification this PCE was increased to 3.13%. Further increases in PCE to 5.54% and 7.55% were achieved by using the more advanced donor polymers PTB7-Th and P3TEA, respectively. The simple yet high performance devices coupled with the highly modular and scalable "acceptor" synthesis make fullerene-free organic solar cells an attractive and cost-effective clean energy technology.

Four electron deficient small molecules based on the diketopyrrolopyrrole (DPP) chromophore were synthesized using microwave-assisted direct arylation reactivity.

Demonstration of the utility of a commercially available heterogeneous palladium catalyst in the synthesis of a relevant high performance molecular semiconductor.

A streamlined synthetic approach to easily access complex pi-conjugated molecular materials.

Symmetrical N‐heterocyclic 1,1′,3,3′‐tetrahydro‐2,2′‐bi‐1,3,2‐diazaphospholes and 2,2′‐bi‐1,3,2‐diazaphospholidines are prepared by time‐saving, sequential “one‐pot” syntheses starting from 1,4‐diazabutadienes or N‐alkyl or N‐aryl‐substituted ethane‐1,2‐diamines. This method offers high selectivity and minimizes the loss of products owing to unwanted hydrolysis, and thus grants high product yields. In some cases, secondary phosphanes were formed together with or instead of diphosphanes. This reaction is explained by a follow‐up process involving homolytic fission of diphosphanes to give phosphanyl radicals, which then react with ammonium salts to give a mixture of secondary phosphanes and chlorophosphanes. Even if its synthetic scope is as yet limited, this approach seems promising in offering superior selectivity and higher yields than common synthetic protocols that rely on the use of complex hydrides as reducing agents. In addition to the reductive conversion of diphosphanes into secondary phosphanes, a reverse reaction under exposure of the reactants to light is also reported.

investigated, those based upon the perylene diimide (PDI) skeleton have been extensively studied. [11,12] The PDI chromophore exhibits strong visible light absorption up to ≈600 nm, making it brilliant red in color, and a complimentary absorber to many common high-performance donor polymers. In addition, the dye is a good electron transporting material, is photochemically stable, and can be easily functionalized at the bay, headland, and/or imide position allowing for a myriad of structures to be developed. [13] It has been well documented that monomeric PDI materials often exhibit a strong tendency to aggregate, leading to poor quality bulk heterojunction (BHJ) films and sub-par OSC performance. [14][15][16][17] Dimerization of the PDI chromophores, the formation of higher number oligomers, or polymerization results in nonplanar arrangement of the PDI units, limiting aggregate formation, leading to high performance OSCs. [18][19][20] To date the record PCE for a PDI-based OSC is 9.5%, and is achieved using a dimeric PDI species [21] consisting of two PDI units linked via a spirofluorene building block. Directly linking two PDI mole cules together at the bay position is another strategy to create PDI dimers with highly twisted geometries that lead to good performing OSCs. [22,23] Our research team and others have built upon this concept and developed a series of "annulated" PDI dimers. Annulation at the bay position with sulfur, [24] selenium, [25] or nitrogen [26] has led to several new NFAs that can achieve PCEs above 7% when paired with polymer donors.A key feature to the N-annulated PDI dimers is that the pyrrolic N-atoms offer an additional site for functionalization and open the possibility of side-chain engineering, a valuable tool to tune the BHJ morphology. [27,28] In addition, the dimers can be processed into ordered films using environmentally friendly solvents, [29] which is an important parameter when considering up-scaling. [30][31][32][33] In this work, we report on green-solvent-processable OSCs based on N-annulated PDI dimers and the commercial polymer PTB7-Th. A series of eight different PDI dimers having different alkyl chain lengths and branching points were synthesized and characterized. Through side-chain engineering of the N-annulated PDI dimers, OSC PCEs of 6.6% were achieved.Through ease of scalability and facile synthetic methods, eight N-annulated perylene diimide dimers with different aliphatic chains are synthesized and evaluated as non-fullerene acceptors in organic solar cells (OSCs). Optical absorption and emission spectroscopy, and cyclic voltammetry are used to characterize the materials. Variation of the length and topology of the aliphatic chains attached at the pyrrolic N-position is shown to have minimal effect on properties in solution. As films, the use of a branched aliphatic chains results in the dimer exhibiting a low energy shoulder in the absorption spectrum and a narrower emission band. OSCs are fabricated and tested in air, at room temperature, using an inverted arch...

A new, easily synthesized diphosphine based on a heterocyclic 1,3,2-diazaphospholidine framework has been prepared. Due to the large, sterically encumbering Dipp groups (Dipp = 2,6-diisopropylphenyl) on the heterocyclic ring, the diphosphine undergoes homolytic cleavage of the P-P bond in solution to form two phosphinyl radicals. The diphosphine has been reacted with O(2), S(8), Se, Te, and P(4), giving products that involve insertion of elements between the P-P bond to yield the related phosphinic acid anhydride, sulfide/disulfide, selenide, telluride, and a butterfly-type perphospha-bicyclobutadiene structure with a trans,trans-geometry. All molecules have been characterized by multinuclear NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Variable-temperature EPR spectroscopy was utilized to study the nature of the phosphinyl radical in solution. Electronic structure calculations were performed on a number of systems from the parent diphosphine [H(2)P](2) to amino-substituted [(H(2)N)(2)P](2) and cyclic amino-substituted [(H(2)C)(2)(NH)(2)P](2); then, bulky substituents (Ph or Dipp) were attached to the cyclic amino systems. Calculations on the isolated diphosphine at the B3LYP/6-31+G* level show that the homolytic cleavage of the P-P bond to form two phosphinyl radicals is favored over the diphosphine by ~11 kJ/mol. Furthermore, there is a significant amount of relaxation energy stored in the ligands (52.3 kJ/mol), providing a major driving force behind the homolytic cleavage of the central P-P bond.

In this paper, we report a novel synthesis of anhydrous 1-hydroxy-2,2,6,6-tetramethyl-piperidine (TEMPO-H). An X-ray crystal structure and full characterization of the compound are included. Compared to hydrated TEMPO-H, its anhydrous form exhibits improved stability and a differing chemical reactivity. The reactions of anhydrous TEMPO-H with a variety of low-valent carbon centres are described. For example, anhydrous TEMPO-H was reacted with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes), an unsaturated NHC. Crystals of [CHNC 6 H 2 (CH 3 ) 3 ] 2 C ◊ ◊ ◊ HO-(NC 5 H 6 (CH 3 ) 4 ), IMes ◊ ◊ ◊ TEMPO-H, were isolated and a crystal structure determined. The experimental structure is compared to the results of theoretical calculations on the hydrogen-bonded dimer. Anhydrous TEMPO-H was also reacted with the saturated NHC, 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene (SIPr), giving the product [CH 2 Ni-Pr 2 C 6 H 3 ] 2 CH ◊ ◊ ◊ O(NC 5 H 6 (CH 3 ) 4 ). In contrast, the reaction of hydrated TEMPO-H with 1,3-bis(2,6-diisopropylphenyl)imidazolidin-2-ylidene gave small amounts of the hydrolysis product, N-(2,6-diisopropylphenyl)-N- [2-(2,6-diisopropylphenylamino)ethyl]formamide. Finally, anhydrous TEMPO-H was reacted with (triphenylphosphoranylidene)ketene to generate Ph 3 PC(H)C( O)O(NC 5 H 6 (CH 3 ) 4 ). A full characterization of the product, including an X-ray crystal structure, is described. Scheme 1 Structural isomers formed by the reaction of TEMPO-H (1) with NHCs (2).Access to anhydrous TEMPO-H has not been reported in the literature, but it was clear to us early on that the water in