Abstract:Hexaarylbenzenes (HABs) are valuable precursors for the bottom-up synthesis of (nano-)graphene structures. In this work the synthesis of several bis-pyrimidine substituted HABs furnished with tert-butyl groups at different sites of the four pendant phenyl rings is reported. The synthetic procedure is based on modular [4+2]-Diels-Alder cycloaddition reactions followed by decarbonylation. Analysis of the solid-state structures revealed that the newly synthesized HABs feature a propeller-like arrangement of the s… Show more
Small heteroaryl‐diyne (Het‐DY) tags with distinct vibrational frequencies, and physiologically relevant cLog P were designed for multiplexed bioorthogonal Raman imaging. Pd−Cu catalyzed coupling, combined with the use of Lei ligand, was shown to improve overall yields of the desired heterocoupled Het‐DY tags, minimizing the production of homocoupled side‐products. Spectral data were in agreement with the trends predicted by DFT calculations and systematic introduction of electron‐ rich/poor rings stretched the frequency limit of aryl‐capped diynes (2209–2243 cm−1). The improved Log P of these Het‐DY tags was evident from their diffuse distribution in cellular uptake studies and functionalizing tags with organelle markers allowed the acquisition of location‐specific biological images. LC–MS‐ and NMR‐based assays showed that some heteroaryl‐capped internal alkynes are potential nucleophile traps with structure‐dependent reactivity. These biocompatible Het‐DY tags, equipped with covalent reactivity, open up new avenues for Raman bioorthogonal imaging.
Small heteroaryl‐diyne (Het‐DY) tags with distinct vibrational frequencies, and physiologically relevant cLog P were designed for multiplexed bioorthogonal Raman imaging. Pd−Cu catalyzed coupling, combined with the use of Lei ligand, was shown to improve overall yields of the desired heterocoupled Het‐DY tags, minimizing the production of homocoupled side‐products. Spectral data were in agreement with the trends predicted by DFT calculations and systematic introduction of electron‐ rich/poor rings stretched the frequency limit of aryl‐capped diynes (2209–2243 cm−1). The improved Log P of these Het‐DY tags was evident from their diffuse distribution in cellular uptake studies and functionalizing tags with organelle markers allowed the acquisition of location‐specific biological images. LC–MS‐ and NMR‐based assays showed that some heteroaryl‐capped internal alkynes are potential nucleophile traps with structure‐dependent reactivity. These biocompatible Het‐DY tags, equipped with covalent reactivity, open up new avenues for Raman bioorthogonal imaging.
A series of partially fused N‐doped nanographenes (2–4) are synthesized via the oxidative cyclodehydrogenation of oligoaryl‐substituted dibenzo[e,l]pyrene (1), and five, six, and seven new C−C bonds are formed, respectively, implying stepwise C−C bond fusion and extended π‐conjugation. Single‐crystal X‐ray diffraction analysis of compound 4 a revealed that the presence of sterically demanding groups hindered the formation of planar and fully fused nanographene in the oxidative cyclodehydrogenation reaction step. Optical study of compounds 2 to 4 showed that extended π‐conjugation leads to a regular stepwise bathochromic shift in the absorption and emission spectra. Furthermore, the HOMO–LUMO gaps of these compounds exhibit a decrease as C−C bond formation proceeds. Thus, the optoelectronic properties of nanographenes are highly dependent on the formation of new C−C bonds in the molecular skeleton.
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