Potassium Cryptate of a Macrobicyclic Ligand Featuring a Reducible hexakis(phenylthio)benzene electron-acceptor site

"The Sulfur Dance" Around Arenes and Heteroarenes - the Reversible Nature of Nucleophilic Aromatic Substitutions

We disclose the features of a category of reversible nucleophilic aromatic substitutions in view of their significance and generality in dynamic aromatic chemistry. Exchange of sulfur components surrounding arenes and heteroarenes may occur at 25 °C, in a process that one may call a "sulfur dance". These SNAr systems present their own features, apart from common reversible reactions utilized in dynamic covalent chemistry (DCC). By varying conditions, covalent dynamics may operate to provide libraries of thiaarenes with some selectivity, or conversion of a hexa(thio)benzene asterisk into another one. The reversible nature of SNAr is confirmed by three methods: a convergence of the products distribution in reversible SNAr systems, a related product redistribution between two per(thio)benzenes by using a thiolate promoter, and from kinetic/thermodynamic data. A four-component dynamic covalent system further illustrates the thermodynamically-driven formation of a thiacalix[2]arene[2]pyrimidine by sulfur component exchanges. This work stimulates the implementation of reversible SNAr in aromatic chemistry and in DCC.

Making multi-twisted luminophores produce persistent room-temperature phosphorescence

Multi-twisted molecules, especially those with more than four branched rotation axes, have served as superior prototypes in diverse fields like molecular machines, optical materials, sensors, and so forth. However, due to excessive non-radiative relaxation of these molecules, it remains challenging to address their persistent room-temperature phosphorescence (pRTP), which limits their further development. Herein, we develop a host-guest energy-transfer relay strategy to improve the phosphorescence lifetime of multi-twisted luminophores by over thousand-fold to realize pRTP, which can be witnessed by the naked eye after removing the excitation light source. Moreover, we employ photoexcitation-induced molecular rearrangement to further prolong the phosphorescence lifetime, which, to the best of our knowledge, is the first example of photoactivation in ordered host-guest systems. Our systems show superior humidity and oxygen resistance, enabling long-term (at least over 9-12 months) stability of the pRTP properties. By achieving pRTP of multi-twisted luminophores, this work can advance the understanding of molecular photophysical mechanisms and guide the study of more molecular systems that are difficult to achieve pRTP.

Dynamic self-correcting nucleophilic aromatic substitution

Dynamic covalent chemistry, with its ability to correct synthetic dead-ends, allows for the synthesis of elaborate extended network materials in high yields. However, the limited number of reactions amenable to dynamic covalent chemistry necessarily confines the scope and functionality of materials synthesized. Here, we explore the dynamic and self-correcting nature of nucleophilic aromatic substitution (S_NAr), using ortho-aryldithiols and ortho-aryldifluorides that condense to produce redox-active thianthrene units. We demonstrate the facile construction of two-, three- and four-point junctions by reaction between a dithiol nucleophile and three different model electrophiles that produces molecules with two, three and four thianthrene moieties, respectively, in excellent yields. The regioselectivity observed is driven by thermodynamics; other connections form under kinetic control. We also show that the same chemistry can be extended to the synthesis of novel ladder macrocycles and porous polymer networks with Brunauer-Emmett-Teller surface area of up to 813 m² g^-1.

Practical synthesis of 5-aryl-3-alkylsulfonyl-phenol and 5-aryl-3-arylsulfonyl-phenol libraries

A straightforward and cost-effective synthesis of 5-aryl-3-alkylsulfonyl-phenols by a sequential scaffold derivatization strategy has been developed. The procedure is suitable for parallel synthesis of small libraries around the biphenyl privileged core having an unusual 1,3,5-substitution pattern. The synthesis is exemplified by a pilot library of 30 compounds.

Persulfurated Aromatic Compounds

Persulfurated arenes have been known for about 50 years but they were underexploited in chemistry in spite of facile, mild, and high-yielding syntheses. Their properties (redox potentials, UV/Vis absorption, conductivity, nonlinear optical properties, etc.) are mainly due to the aromaticity of the ring with sp2-hybridized carbon atoms and to the electronic contribution from numerous divalent sulfur ligands, which also stabilize negative or positive charges. The characteristic conformational patterns of the sulfur ligands often facilitate preorganization in supramolecular assemblies, with or without thiophilic metal cations, for designing redox sensors, ion-selective membranes, clathrates, organic conductors, nonlinear optical materials, liquid crystals, coordination polymers, and bioinorganic systems. A new class of supramolecules with various molecular shapes such as asterisks, chains, wheels, and windmills were reported.

Electron transfer through molecular bridges between reducible pentakis(thiophenyl)benzene subunits

"Dimers" 3, 4 and 7, which consist of two reducible pentakis(thiophenyl)benzene subunits linked by different molecular structures, have been synthesised as model compounds for reducible molecular-wire-type synthons to represent differences in the electron-transfer ability as a function of the bridging structure. The bridging units consist of para-divinylbenzene in 3, bis-hydrazone in 4 and diacetylene in 7. Their ability to transfer electrons from one reducible subunit to the other was investigated by electrochemical and spectroelectrochemical methods and, in the case of 4 and 7, the solid-state structures support the experimental findings. The para-divinylbenzene bridge in 3 was found to completely isolate the reducible structures (Class I system). In contrast, the diacetylene bridge in 7 electronically connects the two reducible structures (Class III system) and, thus, demonstrates its potential application as a "molecular wire". The bis-hydrazone-linked compound 4 displayed only a low level of electronic connection between the subunits and was only observed in the spectroelectrochemical investigation.