Electron transfer reactions can now be followed at the single-molecule level, but the connection between the microscopic and macroscopic data remains to be understood. By monitoring the conductance of a single molecule, we show that the individual electron transfer reaction events are stochastic and manifested as large conductance fluctuations. The fluctuation probability follows first-order kinetics with potential dependent rate constants described by the Butler–Volmer relation. Ensemble averaging of many individual reaction events leads to a deterministic dependence of the conductance on the external electrochemical potential that follows the Nernst equation. This study discloses a systematic transition from stochastic kinetics of individual reaction events to deterministic thermodynamics of ensemble averages and provides insights into electron transfer processes of small systems, consisting of a single molecule or a small number of molecules.

Cyclopenta­[b]­thiopyran, isomeric to benzo­[b]­thiophene while isoelectronic to azulene, is involved as a building block to construct soluble organic semiconductors for field-effect transistors. Two series of angular-shaped heteroarenes based on cyclopenta­[b]­thiopyran, that is, C n -SS (n = 4, 6, 8, 10) with different linear alkyl groups and C 8 -SS-Cl m (m = 2, 3, 4) with chlorides substituted at different positions, have been straightforward synthesized. The obtained seven S-heteroarenes exhibit intriguing and similar photophysical and electrochemical properties, such as near-infrared absorption and high-energy levels of the highest occupied molecular orbitals. Nevertheless, the S-heteroarenes with identical π-conjugated skeletons demonstrate completely different molecular packing structures, which is proofed to be the key determinate factor for the charge carrier mobilities. Upon the engineering of the pendant alkyl lengths, the highest hole mobility in the C n -SS series is achieved for C 8 -SS (1.1 cm2 V–1 s–1) with moderate alkyl length. The further incorporation of chlorides on C 8 -SS results in the shortened intermolecular H···S contacts and the interplane distances. Most interestingly, when chlorine-containing chloroform and chlorobenzene are used as crystallization solvents, single crystals of C 8 -SS-Cl m with different packing structures are produced owing to the intermolecular interactions among the solute and solvent molecules. Upon further engineering of the chlorination position and the crystallization solvent, the maximum hole mobility in the ambient air improves to 2.7 cm2 V–1 s–1 for C 8 -SS-Cl 2 crystallized from chlorobenzene, suggesting that the introduction of the accessible chlorides is a feasible pathway to engineering the crystal structures and controlling the charge transport characteristics.

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BN‐embedded oligomers with different pairs of BN units were synthesized by electrophilic borylation. Up to four pairs of BN units were incorporated in the large polycyclic aromatic hydrocarbons (PAHs). Their geometric, photophysical, electrochemical, and Lewis acidic properties were investigated by X‐ray crystallography, optical spectroscopy, and cyclic voltammetry. The B−N bonds show delocalized double‐bond characteristics and the conjugation can be extended through the trans‐orientated aromatic azaborine units. Calculations reveal the relatively lower aromaticity for the inner azaborine rings in the BN‐embedded PAH oligomers. The frontier orbitals of the longer oligomers are delocalized over the inner aromatic rings. Consequently, the inner moieties of the BN‐embedded PAH oligomers are more active than the outer parts. This is confirmed by a simple oxidation reaction, which has significant effects on the aromaticity and the intramolecular charge‐transfer interactions.

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Electron-donating triphenylamine and/or electron-withdrawing pyromellitic diimide (PMDI) are functionalized on dithienylethene (DTE) and three novel photochromic materials have been designed and successfully synthesized. All the compounds display reversible photochromism due to the molecular switching between ring-closed isomers upon UV light irradiation and ring-open isomers upon exposure to visible light. Thus they can be applied as an anti-counterfeiting ink. Moreover, the study of the photoswitching kinetics reveals that both the ring-closing and ring-opening reactions are first-order reactions. Further charge population analysis discovers that the electron densities of the substituents at the DTE core have a dramatic influence on the photochromic properties. The incorporation of electron-donating triphenylamine groups at the α-position of the thiophene rings in the DTE unit facilitates the ring-closing reaction upon UV light irradiation. In contrast, the substitution of an electron-withdrawing PMDI unit in the DTE unit is beneficial to the ring-opening reaction upon irradiation of visible light. This work may help to understand the photochromism of DTE derivatives and provide a pathway for designing DTE-based photochromes with more or less sensitivity to UV or visible light.

Six-membered azaborine rings have been straightforwardly fused on naphthalimide-based donor-acceptor systems, and a series of BN-containing heteroaromatic compounds BN1-BN3 were constructed. Electron-donating triphenylamines were functionalized in the extended direction of the 3- or/and 4-position of the naphthalimide unit. For comparison, reference BN0 without triphenylamine was also prepared. The intramolecular charge transfer (ICT) interactions in the resulting BN-fused naphthalimides (BN0-BN3) together with their precursors (N0-N3) and fluoride-coordinated analogues (FBN0-FBN3) have been systematically investigated by photophysical, electrochemical, and theoretical approaches. It is found that the fusion of the azaborine ring has a great effect on the ICT properties of the D-A systems based on BN-fused naphthalimides. For the precursors without boron, the extension of an electron donor from the 3-position of naphthalimide is superior in enhancing the D-A interactions. On the contrary, upon fusion of the azaborine ring on naphthalimide, the dominant orientation of the ICT interactions conversely converts to the extended direction of the 4-position of naphthalimide in the D-A molecules based on BN-fused naphthalimides. Most interestingly, upon coordinating the boron by a fluoride ion, the ICT interactions are dramatically enlarged and the substitution position of the triphenylamino group has a negligible effect on the ICT properties of the fluoride-coordinated analogues.

A heterocycloarene derivative (S-Octulene) possessing two sulfur atoms was conveniently synthesized through Bi(OTf)3-catalyzed cyclization from a macrocyclic tetramethoxyethenylated precursor. The physical properties of S-Octulene and its supramolecular host-guest interaction with...