Current methods for constructing amide bonds join amines and carboxylic acids by dehydrative couplings-processes that usually require organic solvents, expensive and often dangerous coupling reagents, and masking other functional groups. Here we describe an amide formation using primary amines and potassium acyltrifluoroborates promoted by simple chlorinating agents that proceeds rapidly in water. The reaction is fast at acidic pH and tolerates alcohols, carboxylic acids, and even secondary amines in the substrates. It is applicable to the functionalization of primary amides, sulfonamides, and other N-functional groups that typically resist classical acylations and can be applied to late-stage functionalizations.

Perylene diimide (PDI) is a workhorse of the organic electronics community. However, the vast majority of designs that include PDI substitute the core with various functional groups to encourage intimate cofacial contacts between largely planar PDIs. Over the past several years, we have observed the counterintuitive result that contorting the planar aromatic core of PDI leads to higher performing photovoltaics, photodetectors, batteries, and other organic electronic devices. In this Perspective, we describe how different modes of contortion can be reliably installed into PDI-based molecules, oligomers, and polymers. We also describe how these different contortions modify the observed optical and electronic properties of PDI. For instance, contorting PDIs into bowls leads to high-efficiency singlet fission materials, while contorting PDIs into helicene-like structures leads to nonlinear amplification of Cotton effects, culminating in the highest g-factors so far observed for organic compounds. Finally, we show how these unique optoelectronic properties give rise to higher performance organic electronic devices. We specifically note how the three-dimensional structure of these contorted aromatic molecules is responsible for the enhancements in performance we observe. Throughout this Perspective, we highlight opportunities for continued study in this rapidly developing organic materials frontier.

We report the synthesis of enantiomerically pure carbo[6]helicene oligomers with buta-1,3-diyne-1,4-diyl bridges between the helicene nuclei. The synthesis of monomeric (±)-2,15-bis[(triisopropylsilyl)ethynyl]carbo[6]helicene was achieved in 25 % yield over six steps. Pure (+)-(P)- and (-)-(M)-enantiomers were obtained by HPLC on a chiral stationary phase. The dimeric (+)-(P) - and (-)-(M) -configured and the tetrameric (+)-(P) - and (-)-(M) -configured oligomers were obtained by sequential oxidative acetylenic coupling. The ECD spectra of the tetrameric oligomers displayed large Cotton effect intensities of Δϵ=-851 m cm at λ=370 nm ((M) -enantiomer). We transformed the buta-1,3-diyne-1,4-diyl bridge in the dimeric (P) and (M) oligomer by heteroaromatization into a thiene-2,5-diyl linker. Although the resulting chromophore showed reduced ECD intensities, it exhibited a remarkably strong fluorescence emission at 450-500 nm, with an absolute quantum yield of 25 %.

We present an investigation of the photocyclization of novel aromatic diarylethene (DAE) systems 1-3 based on pyrazine, quinoxaline, and helicene scaffolds. These prospective photoswitches were designed using DFT calculations and analyzed in solution and in the solid state by cyclic and rotating disc voltammetry, UV-Vis and transient absorption spectroscopy, as well as X-ray crystallography. Additionally, Nucleus Independent Chemical Shift (NICS) calculations were performed to investigate the influence of the aromaticity on the photocyclization ability. While pyrazine-2,3-diyl-extended DAE system 1 demonstrated photoswitching ability with short lifetimes of the cyclized form, the more aromatic quinoxaline analogue 2 did not feature any photocyclization. Further extension of these aromatic systems into helicene-DAE 3 resulted in stabilization of the cyclized form through the conserved backbone aromaticity, accompanied by

We report a reliable way to manipulate the dynamic, axial chirality in perylene diimide (PDI)-based twistacenes. Specifically, we reveal how chiral substituents on the imide position induce the helicity in a series of PDI-based twistacenes. We demonstrate that this remote chirality is able to control the helicity of flexible [4]­helicene subunits by UV–vis, CD spectroscopy, X-ray crystallography, and TDDFT calculations. Furthermore, we have discovered that both the chiral substituent and the solvent each has a strong impact on the sign and intensity of the CD signals, highlighting the control of the dynamic helicity in this flexible system. DFT calculations suggest that the steric interaction of the chiral substituents is the important factor in how well a particular group is at inducing a preferred helicity.