N-Oxide S-O chalcogen bonding in conjugated materials

Tuning the Electronic Properties of Bridged Dithienyl-, Difuryl-, Dipyrrolyl-Vinylene as Precursors of Small-Bandgap Conjugated Polymer

Optoelectronic properties of linear π-conjugated polymers/oligomers are of great importance for the fabrication of organic photonic and electronic devices. To this end, the π-conjugated polymers/oligomers need to meet both optoelectronic and key structural properties in order to fulfill their implementation as active components. In particular, they need to possess low bandgap and high thermal, conformational, and photochemical stabilities. So far, several strategies have been developed to attain such requirements including the covalent and non-covalent rigidification concepts of the π-conjugated systems. On the basis of these findings, we describe herein the theoretical studies of novel series of covalently bridged derivatives demonstrating the benefits of the strategy. Comparison of these derivatives with compounds previously described in the literature highlights enhanced optoelectronic properties and behaviors that would be beneficial for the construction and development of new linear π-conjugated polymers.

Lest We Forget-The Importance of Heteroatom Interactions in Heterocyclic Conjugated Systems, from Synthetic Metals to Organic Semiconductors

The field of synthetic metals is, and remains, highly influential for the development of organic semiconductor materials. Yet, with the passing of time and the rapid development of conjugated materials in recent years, the link between synthetic metals and organic semiconductors is at risk of being forgotten. This review reflects on one of the key concepts developed in synthetic metals - heteroatom interactions. The application of this strategy in recent organic semiconductor materials, small molecules and polymers, is highlighted, with analysis of X-ray crystal structures and comparisons with model systems used to determine the influence of these non-covalent short contacts. The case is made that the wide range of effective heteroatom interactions and the high performance that has been achieved in devices from organic solar cells to transistors is testament to the seeds sown by the synthetic metals research community.

Cross-Electrophile C-PIII Coupling of Chlorophosphines with Organic Halides: Photoinduced PIII and Aminoalkyl Radical Generation Enabled by Pnictogen Bonding

Pnictogen bonding (PnB) has gained recognition as an appealing strategy for constructing novel architectures and unlocking new properties. Within the synthetic community, the development of a straightforward and much simpler protocol for cross-electrophile C-PIII coupling remains an ongoing challenge with organic halides. In this study, we present a simple strategy for photoinduced PnB-enabled cross-electrophile C-PIII couplings using readily available chlorophosphines and organic halides via merging single electron transfer (SET) and halogen atom transfer (XAT) processes. In this photomediated transformation, the PnB formed between chlorophosphines and alkyl amines facilitates the photogeneration of PIII radicals and α-aminoalkyl radicals through SET. Subsequently, the resulting α-aminoalkyl radicals activate C-X bonds via XAT, leading to the formation of carbon radicals. This methodology offers operational simplicity and compatibility with both aliphatic and aromatic chlorophosphines and organic halides.

Strategies for the Design of PEDOT Analogues Unraveled: the Use of Chalcogen Bonds and σ-Holes

In this theoretical study, we set out to demonstrate the substitution effect of PEDOT analogues on planarity as an intrinsic indicator for electronic performance. We perform a quantum mechanical (DFT) study of PEDOT and analogous model systems and demonstrate the usefulness of the ωB97X-V functional to simulate chalcogen bonds and other noncovalent interactions. We confirm that the chalcogen bond stabilizes the planar conformation and further visualize its presence via the electrostatic potential surface. In comparison to the prevalent B3LYP, we gain 4-fold savings in computational time and simulate model systems of up to a dodecamer. Implications for design of conductive polymers can be drawn from the results, and an example for self-doped polymers is presented where modulation of the strength of the chalcogen bond plays a significant role.

Alkyl Sulfonyl Fluorides Incorporating Geminal Dithioesters as SuFEx Click Hubs via Water-Accelerated Organosuperbase Catalysis

Sulfur(VI) fluoride exchange (SuFEx) is recognized as another emerging tool for click chemistry. The preparation of the functionalized alkyl sulfonyl fluorides as key SuFEx hubs via C(sp³)-C(sp³) bond formation is exceptionally challenging. We report herein a new efficient method for accessing alkyl sulfonyl fluorides incorporating γ-geminal dithioester via phosphazene catalysis. The aqueous, neutral organosuperbase catalytic system amplifies the reactivity by taking advantage of the hydrophobic amplification. SuFEx-active products are applied to the click connection of bioactive molecules. Density functional theory studies show that the selective outcome of the product is guided by an ion-pair organosuperbase catalyst assembly that is potentially stabilized by a hydrogen-bonding interaction between the catalyst and the DTM in the C(sp³)-C(sp³) bond-forming transition structure.

Non-covalent interactions (NCIs) in π-conjugated functional materials: advances and perspectives

The design and development of functional materials with real-life applications are highly demanding. Understanding and controlling inter- and intra-molecular interactions provide opportunities to design new materials. A judicious manipulation of the molecular structure significantly alters such interactions and can boost selected properties and functions of the material. There is burgeoning evidence of the beneficial effects of non-covalent interactions (NCIs), showing that manipulating NCIs may generate functional materials with a wide variety of physical properties leading to applications in catalysis, drug delivery, crystal engineering, etc. This prompted us to review the implications of NCIs on the molecular packing, optical properties, and applications of functional π-conjugated materials. To this end, this tutorial review will cover different types of interactions (electrostatic, π-interactions, metallophilic, etc.) and their impact on π-conjugated materials. Attempts have also been made to delineate the effects of weak interactions on opto-electronic (O-E) applications.

Chalcogen bond-assisted syn-locked scaffolds: DFT analysis and biological implications of novel tubulin inhibitors

A series of new tubulin inhibitors containing chalcogen bonds have been discovered. Density functional theory (DFT) analysis of the O-C-C-S torsion profile shows a preference of 0.8 kcal/mol for the syn-conformer over the anti-conformer. Besides, the O-S natural bond orbital (NBO) analysis reveals that the O_LP ∼ C-S_BD∗ energy potential is 0.62 kcal/mol. Further pharmacochemical screening of several series of (4-arylthiophen-2-yl)(3,4,5-trimethoxyphenyl)methanones identified IPO-10 as a highly effective tubulin inhibitor with an IC₅₀ of 23 nm for MCF-7.

An N-oxide containing conjugated semiconducting polymer with enhanced electron mobility via direct (hetero)arylation polymerization

The N-oxide containing conjugated semiconducting polymer is synthesized by direct (hetero)arylation polymerization and exhibit enhanced electron mobility compared to its non-oxide analogous polymer.

Alkynyl Sulfonium Salts Can Be Employed as Chalcogen-Bonding Catalysts and Generate Alkynyl Radicals under Blue-Light Irradiation

Chalcogen bonding (ChB) has emerged as a promising tool in organic synthesis. However, compared with the well-developed selenium- and tellurium-based salt catalysts, the ChB catalysis of sulfonium salts is still unknown. Here, we report a new type of alkynyl-sulfonium salt ChB catalysis for various ionic transformations, including transfer hydrogenation, bromination, bromolactonization, dimerization of 1,1-diphenylethylene, nitro-Michael addition reaction and Ritter reaction. More importantly, the photocapability of ChB was first demonstrated to generate alkynyl radicals for the synthesis of a variety of chalcogenoacetylenes. Mechanistic studies shed light on the mechanism of the photoinduced reactions and confirmed the involvement of alkynyl radicals which are difficult to generate otherwise.

Sulfuroxygen interaction-controlled (Z)-selective anti-Markovnikov vinyl sulfides

The sulfur oxygen (SO) interaction was used herein to obtain (Z)-selective anti-Markovnikov vinyl sulfides from the addition of thiyl radicals to terminal alkynes. DFT calculations predicted that SO interaction originated from the delocalization of the lone-pair of the carbonyl oxygen to the adjacent σ* orbital of the S atom of C-S.

NaOH-Intercalated Iron Chalcogenides (Na1-xOH)Fe1-yX (X = Se, S): Ion-Exchange Synthesis and Physical Properties

The discovery of the (Li_1-xFe_xOH)FeSe superconductor has aroused significant interest in metal hydroxide-intercalated iron chalcogenides. However, all efforts made to intercalate NaOH between FeSe and FeS layers have failed so far. Here we report two NaOH-intercalated iron chalcogenides (Na_1-xOH)Fe_1-yX (X = Se, S) that were synthesized by a low-temperature hydrothermal ion-exchange method. Their crystal structures were solved through single-crystal X-ray diffraction and refined against powder X-ray and neutron diffraction data. Different from the (Li_1-xFe_xOH)FeX superconductors that crystallize in a tetragonal space group P4/nmm with Z = 2, (Na_1-xOH)Fe_1-yX belong to an orthorhombic space group Cmma with Z = 4. The structural solution also reveals that there are vacancies in both Na and Fe sites and there are not iron ions in the (Na_1-xOH) layer. This is probably why both Fe(II) and Fe(III) species exist in the title compounds, as detected by X-ray photoelectron spectroscopy. Based on magnetization and electrical resistivity measurements, the two compounds were found to be paramagnetic semiconductors. The absence of superconductivity should be closely related to the iron vacancies in the Fe_1-yX layer. Theoretical calculations suggest that inducing superconductivity in (Na_1-xOH)Fe_1-ySe is promising due to the similarity of the electronic structures between stoichiometric (NaOH)FeSe and the (Li_1-xFe_xOH)FeSe superconductor.