Core-expanded pyrenes exhibit rainbow solvatochromism, reversible acidochromism in both solution and solid-state, and reversible crystal-to-crystal mechanochromism all governed by substitution pattern.

Herein we present a clarification of the ambiguous persistence of the 10-methyl-9-phenylacridanyl, 9-phenylxanthenyl, and 9-phenylthioxanthenyl radicals in electrochemical experiments. Each of these radicals has separately been the subject of conflicting literature results for decades with publications claiming both their chemical inertness and propensity to dimerize. We assert that each radical is persistent at conventional electrochemical time scales up to several minutes based on reversible redox couples and cyclic voltammogram simulations of the radicals and their respective cations. All three radicals are rapidly consumed by aerial O, which lends irreversibility to the redox couples after fewer than 20 s of exposure to air. With appreciation for the O sensitivity of these radicals, their electrochemically generated UV-visible absorption spectra have been acquired and matched to predictions made by TD-DFT calculations. Further, we propose that previous claims to have electrochemically measured radical-radical dimerizations have only observed reaction of these radicals with dissolved O.

Saddle-shaped 21,23-dithiadiacenaphtho[1,2-c]porphyrin exhibits binding interaction with [60]fullerene in addition to photon absorption bands extending to 1000 nm.

Three chemodosimeters that exhibit up to 3000-fold enhancement in turn-on visible colour and emission in the presence of oxophilic metal cations.

A monomer‐through‐pentamer series of oligo(1,8‐pyrenylene)s was synthesized using a two‐step iterative synthetic strategy. The trimer, tetramer, and pentamer are mixtures of atropisomers that interconvert slowly at room temperature (as shown by variable‐temperature NMR analysis). They are liquids well below room temperature, as indicated by POM, DSC and SWAXS analysis. These oligomers are highly fluorescent both in the liquid state and in dilute solution (λF,max = 444–457 nm, φF = 0.80) and an investigation of their photophysical properties demonstrated that delocalization plays a larger role in their excited states than it does in related pyrene‐based oligomers.

Tethering of two shape mismatched donors and acceptor leads to an unusual mesogen design.

This case study provides evidence for the appearance of multiple aggregation forms of a single organic dye, arising from its packing polymorphs in the solid state. Each aggregate can be...

Exploration of the sterically‐congested ethane diethyl dixanthenyl‐9,9′‐dicarboxylate has revealed the dynamic behavior arising from its congested C−C bond. Interlocking ‘geared’ substituents and favorable dispersion interactions around this bond result in a conformational preference for partially cofacial xanthene moieties both in solid state and as dilute solutions. The weak, centrally located C−C bond is 1.628 Å long and permits selective thermolysis to yield two carbon‐centered ethyl xanthenyl‐9‐carboxylate radicals, which dimerize with high fidelity into the original sterically‐congested ethane. Recombination of the radicals into this symmetrical head‐to‐head dimer is highly reproducible – by observing the equilibrium, the bond dissociation enthalpy was calculated to be 20.4 kcal ⋅ mol−1. The substituents around the central carbon provide insufficient stabilization against oxygen, which consumes the radicals and unbalances the dimer‐radical equilibrium.