Although understanding the conformations and arrangements of conjugated materials as solids is key to their prospective applications, predictive power over these structural factors remains elusive. In this work, substituent effects tune non-covalent interactions between side-chain fluorinated benzyl esters and main-chain terminal arenes, in turn controlling the conformations and interchromophore aggregation of three-ring phenylene-ethynylenes (PEs). Cofacial fluoroarene-arene (ArF-ArH) interactions cause twisting in the PE backbone, interrupting intramolecular conjugation as well as blocking chromophore aggregation, both of which prevent the typically observed bathochromic shift observed upon transitioning PEs from solution to solid. This work highlights two structural factors that determine whether the ArF-ArH interactions, and the resulting twisted, unaggregated chromophores, occur in these solids: (i) the electron-releasing characteristic of substituents on ArH, with more electron-releasing character favoring ArF-ArH interactions, and (ii) the fluorination pattern of the ArF ring, with 2,3,4,5,6-pentafluorophenyl favoring ArF-ArH interactions over 2,4,6-trifluorophenyl. These trends indicate that considerations of electrostatic complementarity, whether through a polar-π or substituent-substituent mechanism, can serve as an effective design principle in controlling the interaction strengths, and therefore the optoelectronic properties, of these molecules as solids.

Alkyl chain length tunes the reversion temperature of mechanofluorochromic phenylene-ethynylenes that show reversible force-induced change of fluorescence from green to orange.

Although fluorescent probes for the detection of singlet oxygen (O) have been an active area of research, most such probes rely upon change in intensity of a single band. Herein, we report a FRET-based, O-sensitive aqueous suspension of conjugated polymer nanoparticles (CPNs) comprising the energy-donating host polymer poly[{9,9-dioctyl-2,7-divinylene-fluorenylene}-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] doped with an energy acceptor, the O-sensitive thienoacene 5,12-bis(4-methoxyphenyl)-2-butyltetraceno[2,3-b]thiophene. Using a phthalocyanine-based sensitizer, IRDye 700DX, our probe shows a rapid, ratiometric response to photosensitized O in water in both cuvettes and 96-well plates that compares favorably to the commercial O-sensitive dye, singlet oxygen sensor green. The response to irradiation of even nanomolar concentrations of photosensitizer demonstrates the sensitivity of our ratiometric probe.

Diphenylacetylene (tolan) derivatives with self-complementary aryl halides and halogen bond-accepting nitriles form 2D bricklayer packing motifs when halogen bonding occurs. When halogen bonding is absent, as occurred with fluorinated aryl bromides, the molecules adopt other packing motifs. These results suggest halogen bonding is potentially useful for producing rarely observed 2D bricklayer motifs in organic semiconductors.

Although acenes with more than three fused rings can both fluoresce efficiently and react with singlet oxygen ( 1 O 2 ) rapidly, their hydrophobic nature presents a challenge to their use in aqueous environments. Herein we report a series of fluorescent, water-soluble random copolymers that each comprise (oligoethylene glycol) methacrylate (OEGMA) and one of several diarylacene methacrylates, including a tetracene methacrylate and a tetraceneothiophene methacrylate. Exposure to 1 O 2 in water oxidizes the pendant acenes, resulting in diminution of their fluorescence intensities. The observed rate of oxidation of the tetracene-containing polymers compares favorably with a commercial 1 O 2 -sensitive dye. Polymers that also include energy-donating coumarin side chains show ratiometric fluorescence changes in response to 1 O 2 .