Conjugation Extension and Halochromic Behaviors of S‐Fused Polycyclic Aromatic Hydrocarbons Bearing Cyclopenta[b]thiopyran Moieties

Abstract

Three S‐fused polycyclic aromatic hydrocarbons (PAHs) bearing cyclopenta[b]thiopyran moieties have been designed and successfully synthesized. With the conjugation extension, the absorption onset of the longest PAH reaches 1110 nm. All the three S‐fused PAHs exhibit significant halochromic properties in both solution and solid states. Upon protonation, the proton is incorporated on the cyclopentadiene ring while the positive charge is localized on the thiopyrylium ring. Moreover, no significant difference can be found for the two shorter PAHs upon the protonation by different organic acids, such as trifluoroacetic acid (TFA) and trifluoromethanesulfonic acid (TfOH), while the longest PAH can be only mono‐protonated by TFA but di‐protonated by stronger TfOH. Furthermore, after protonation, the non‐emissive S‐fused PAHs exhibit strong fluorescence and can be regenerated by simply neutralization with triethylamine. The enhanced emission of mono‐protonated products stem from S2→S0 transitions, which disobey the Kasha's rule.

Direct Access to Functionalized Azulenes and Pseudoazulenes via Unconventional Alkyne Cyclization Reactions

“…However, this cyclization reaction is deactivated by the electron deficient 4-trifluoromethyl phenyl group substituted on the alkyne. Later, the group successfully extended inserted heteroaromatic rings to include selenophene, [32] tellurophene, [33] and thieno[3,2-b]thiophene rings, [34] affording a series of novel pseudoazulenes containing these heavier chalcogen atoms (Scheme 16). It should be noted that due to the susceptibility of tellurophene to transition metal complexes, [35] PtCl 2 coordinated with strongly π-accepting phosphine ligand P(C 6 F 5 ) 3 was found to be the effective catalyst for ring expansion of tellurophenes to telluropyrans.…”

Thiopyran-Fused Polycyclic Aromatic Compounds Synthesized via Pt(II)-Catalyzed One-Pot Ring-Expansion and 6-endo Cyclization Reactions

“…S-fused polycyclic aromatic hydrocarbons (PAHs) have gained much attention due to their widespread applications in optoelectronic devices, such as light-emitting diodes, , organic photovoltaics, , and field-effect transistors. , Among various S-containing heterocycles, the five-membered thiophene ring is one of the most representative building blocks. − The fused thiophene ring in PAHs can be simply introduced by locking two single-bond-linked segments with a sulfur atom. − Alternatively, S-fused PAHs can be synthesized via conventional cyclization reactions from thiophene-containing precursors. − For example, 1-ethynyl-2-thienyl-substituted aromatics can be converted to benzo­[ b ]­thiophene undergoing classic 6- endo cyclization reaction with the assistance of transition-metal-based catalysts (Figure a), such as indium, − ruthenium, aurum, and platinum. , In comparison to the abundant synthetic methodologies toward S-fused PAHs containing five-membered thiophene rings, fewer reports have focused on their analogues consisting of six-membered thiopyran rings, − most likely due to their different electronic structures and more challenging syntheses. Since thiopyran-fused PAHs present intriguing optoelectronic properties, − such as near-infrared absorption, low oxidation potential, and high charge carrier mobility, the construction of thiopyran-fused PAHs still remains challenging.…”

Reducing Contact Resistance in Organic Field-Effect Transistors: A Comprehensive Comparison between 2D and Microrod Single Crystals

“…A series of nonalternant hydrocarbons containing cyclopentane­[ b ]­thiopyran moieties have been used in OFETs, due to their intense intermolecular S···π and S···S interactions that can enhance hole mobility in the devices. − Hence, 7,14-dioctylnaphtho­[2,1- f :6,5- f ′]­bis­(cyclopentane­[ b ]­thiopyran) (C 8 -SS) is employed to prepare both 2D and microrod single crystals through a simple solution process, based on which two types of OFETs (2D and microrod OFETs) are fabricated with mechanically transferred source and drain electrodes. Significantly, although the C 8 -SS 2D and microrod crystals have the same crystalline structure, the 2D and microrod OFETs show distinct transfer and output characteristics that arise from their different contact behaviors.…”