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Abstract Thiol‐disulfide interchange has been a large field of study for both biochemists and physical organic chemists alike due to its prevalence within biological systems and fundamentally interesting dynamic nature. More recently, efforts have been made to harness the power of this reversible reaction to make self‐assembling systems of macrocyclic molecules. However, less effort has focused on the fundamental work of isolating these assemblies and studying the factors that control the assembly and sorting of these emerging cyclic systems. A more complete fundamental understanding of factors controlling such self‐assembly could also improve understanding of the complex systems biology of thiol exchange while also aiding in the design of dynamic thiol assembly to enable applications ranging from drug delivery and biosensing to new materials synthesis. We have shown previously that pnictogen‐assisted self‐assembly enables formation of discrete disulfide macrocycles and cages without competition from polymer formation for a wide variety of alkyl thiols. In this study, we report the expansion of pnictogen‐assisted self‐assembly methods to form disulfide bearing macrocycles from aryl thiol containing ligands, allowing access to previously unreported molecules. These studies complement classical physical organic and chemical biology studies on the rates and products of aryl thiol oxidation to disulfides, and we show that this self‐assembly method revises some prevailing wisdom from these key classical studies by providing new product distributions and new isolable products in cyclic disulfide formation. 

Abstract Herein we report the synthesis and characterization of four donor/acceptor‐fuseds‐indacenes via the late‐stage oxidation of a family of unsymmetrical benzofuran/benzothiophene‐s‐indacene regioisomers. A thorough study of their properties through experimental and computational analysis has revealed the effect of asymmetry on the molecular properties associated with antiaromaticity, as well as a strong correlation between antiaromaticity and intramolecular charge transfer (ICT). The strength of the charge transfer depends on the fusion orientation of the donor and acceptor motifs relative to thes‐indacene core. The two most antiaromatic oxidized isomers exhibit strong evidence of ICT with 30 and 40 nm solvatochromic shifts. 

Abstract Fusion of aromatic subunits to stabilize an antiaromatic core allows the isolation and study of otherwise unstable paratropic systems. A complete study of a series of six naphthothiophene‐fuseds‐indacene isomers is herein described. Additionally, the structural modifications resulted in increased π–π overlap in the solid state, which was further explored through changing the sterically blocking mesityl group to (triisopropylsilyl)ethynyl in three derivatives. The computed antiaromaticity of the six isomers is compared to the observed physical properties, such as NMR chemical shift, UV‐vis, and CV data. We find that the calculations predict the most antiaromatic isomer and give a general estimation of the relative degree of paratropicity for the remaining isomers, when compared to the experimental results. 

Abstract Cycloparaphenylenes (CPPs) are the smallest possible armchair carbon nanotubes, the properties of which strongly depend on their ring size. They can be further tuned by either peripheral functionalization or by replacing phenylene rings for other aromatic units. Here we show how four novel donor–acceptor chromophores were obtained by incorporating fluorenone or 2‐(9H‐fluoren‐9‐ylidene)malononitrile into the loops of two differently sized CPPs. Synthetically, we managed to perform late‐stage functionalization of the fluorenone‐based rings by high‐yielding Knoevenagel condensations. The structures were confirmed by X‐ray crystallographic analyses, which revealed that replacing a phenylene for a fused‐ring‐system acceptor introduces additional strain. The donor–acceptor characters of the CPPs were supported by absorption and fluorescence spectroscopic studies, electrochemical studies (displaying the CPPs as multi‐redox systems undergoing reversible or quasi‐reversible redox events), as well as by computations. The oligophenylene parts were found to comprise the electron donor units of the macrocycles and the fluorenone parts the acceptor units. 

Abstract The phosphaquinolinone scaffold has been previously studied as a modular core for a variety of fluorescent species where use of substituent effects has focused on increasing or decreasing electron density in the core rings. We now report the synthesis and analysis of several pyridine‐containing phosphaquinolinone species exhibiting notable linear conjugation from the aryl‐substituent to electron‐withdrawing pyridyl nitrogen. Varying the nature of the aryl substituent from electron‐withdrawing to electron‐donating leads to the generation of an internal charge‐transfer (ICT) band in the absorbance spectrum, which becomes the dominant absorbance in terms of intensity in the most electron‐rich ‐NMe₂example. This heterocycle exhibits improved photophysical properties compared to others in the set including high quantum yield and considerably red‐shifted emission. The enhanced ICT can be observed in the X‐ray data where a rare example of molecule co‐planarity is observed. Computational data show increased localization of negative charge on the pyridyl nitrogen as the electron‐donating character of the aryl‐substituent increases. 

Abstract Cyclophanes are a fundamentally interesting class of compounds that host a wide range of unique and emergent properties. However, synthesis of complex and/or functionalized cyclophanes can often suffer from harsh reaction conditions, long reaction times, and sometimes low yields using stepwise methods. We have previously reported an efficient, high‐yielding, metalloid‐directed self‐assembly method to prepare disulfide, thioether, and hydrocarbon cyclophanes and cages that feature mercaptomethyl‐arenes as starting materials. Herein, we report the synthesis of 21 new disulfide and thioether assemblies that expand this high yielding self‐assembly method to a wide breadth of macrocycles and cages with diverse structures. Remarkably, the high‐yielding, efficient syntheses still proceed under dynamic covalent control using electron‐deficient, heteroaryl, cycloalkyl, spiro, and even short alkenyl/alkynyl substrates. 

Abstract Inclusion of a second nitrogen atom in the aromatic core of phosphorus‐nitrogen (PN) heterocycles results in unexpected tautomerization to a nonaromatic form. This tautomerization, initially observed in the solid state through X‐ray crystallography, is also explained by computational analysis. We prepared an electron deficient analogue (2 e) with a fluorine on the pyridine ring and showed that the weakly basic pyridine resisted tautomerization, providing key insights to why the transformation occurs. To study the difference in solution vs. solid‐state heterocycles, alkylated analogues that lock in the quinoidal tautomer were synthesized and their different¹H NMR and UV/Vis spectra studied. Ultimately, we determined that all heterocycles are the aromatic tautomer in solution and all but2 eswitch to the quinoidal tautomer in the solid state. Better understanding of this transformation and under what circumstances it occurs suggest future use in a switchable on/off hydrogen‐bond‐directed receptor that can be tuned for complementary hydrogen bonding. 

Abstract Deriving diverse compound libraries from a single substrate in high yields remains to be a challenge in cycloparaphenylene chemistry. In here, a strategy for the late‐stage functionalization of shape‐persistent alkyne‐containing cycloparaphenylene has been explored using readily available azides. The copper‐free [3+2]azide‐alkyne cycloaddition provided high yields (>90 %) in a single reaction step. Systematic variation of the azides from electron‐rich to ‐deficient shines light on how peripheral substitution influences the characteristics of the resulting adducts. We find that among the most affected properties are the molecular shape, the oxidation potential, excited state features, and affinities towards different fullerenes. Joint experimental and theoretical results are presented including calculations with the state‐of‐the‐art, artificial intelligence‐enhanced quantum mechanical method 1 (AIQM1). 

Abstract We describe two novel hybrid receptors combining a phosphorus‐/nitrogen‐containing (PN) phosphonamidate heterocycle with urea recognition units in an arylethynyl backbone. Structural, spectroscopic and computational studies reveal that the origin of superior binding for hydrogen sulfate (HSO₄⁻) anion is correlated with the formation of strong hetero‐complementary hydrogen bonds with the phosphonamidate motif. We further demonstrate that the hybrid host system is capable of capturing/transporting the HSO₄⁻anion from an aqueous, biphasic system. 

Abstract A set of fully‐conjugated indenofluorenes has been synthesized and confirmed by solid‐state structure analysis. The indeno[2,1‐c]fluorenes and their benzo‐fused analogues all contain the antiaromaticas‐indacene core. The molecules possess high electron affinities and show a broad absorption that reaches into the near‐IR region of the electromagnetic spectrum. All of the featured compounds reversibly accept up to two electrons as revealed by cyclic voltammetry. Analysis of molecule tropicity using NICS‐XY scan calculations shows that, while theas‐indacene core is less paratropic thans‐indacene, benz[a]‐annulation further reduces the antiaromaticity of the core. Antiaromatic strength of theas‐indacene core can also be tuned by the position of fusion of additional arenes on the outer rings.