Organotelluroxane molecular clusters assembled via Te⋯X- (X = Cl-, Br-) chalcogen bonding anion template interactions

Key-to-lock halogen bond-based tetragonal pyramidal association of iodonium cations with the lacune rims of beta-octamolybdate

The structure-directing "key-to-lock" interaction of double σ-(IIII)-hole donating iodonium cations with the O-flanked pseudo-lacune rims of [β-Mo8O26]4- gives halogen-bonded iodonium-beta-octamolybate supramolecular associates. In the occurrence of their tetragonal pyramidal motifs, deep and broad σ-(IIII)-holes of a cation recognize the molybdate backbone, which provides an electronic pool localized around the two lacunae. The halogen-bonded I⋯O linkages in the structures were thoroughly studied computationally and classified as two-center, three-center bifurcated, and unconventional "orthogonal" I⋯O halogen bonds. In the latter, the O-atom approaches orthogonally the C-IIII-C plane of an iodonium cation and this geometry diverge from the IUPAC criteria for the identification of the halogen bond.

Bidentate Ligand Driven Intramolecularly Te…O Bonded Organotellurium Cations from Synthesis, Stability to Catalysis

A new series of unsymmetrical phenyl tellurides derived from 2-N-(quinolin-8-yl) benzamide ligand has been synthesized in a practical manner by the copper-catalyzed method by using diaryl ditelluride and Mg as a reductant at room temperature. In order to augment the Lewis acidity of these newly formed unsymmetrical monotellurides, these have been transformed into corresponding unsymmetrical 2-N-(quinolin-8-yl)benzamide tellurium cations. Subsequently, these Lewis acidic tellurium cations were used as chalcogen bonding catalysts, enabling the synthesis of various substituted 1,2-dihydroquinolines by activating ketones with anilines under mild conditions. Moreover, the synthesized 2-N-(quinolin-8-yl)benzamide phenyl tellurium cation has also catalyzed the formation of β-amino alcohols in high regioselectivity by effectively activating epoxides at room temperature. Mechanistic insight by 1 H and 19 F NMR study, electrostatic surface potential (ESP map), control reaction in which tellurium cation reacted explosively with epoxide, suggested that the enhanced Lewis acidity of tellurium center seems responsible for efficient catalytic activities under mild conditions enabling β-amino alcohols with excellent regioselectivity and 1,2-dihydroquinolines with trifluoromethyl, nitro, and pyridylsubstitution, which were difficult to access.

2-Benzamide Tellurenyl Iodides: Synthesis and Their Catalytic Role in CO2 Mitigation

Benzamide-derived organochalcogens (chalcogen=S, Se, and Te) have shown promising interest in biological and synthetic chemistry. Ebselen molecule derived from benzamide moiety is the most studied organoselenium. However, its heavier congener organotellurium is under-explored. Here, an efficient copper-catalyzed atom economical synthetic method has been developed to synthesize 2-phenyl-benzamide tellurenyl iodides by inserting a tellurium atom into carbon-iodine bond of 2-iodobenzamides in one pot with 78-95 % yields. Further, the Lewis acidic nature of Te center and Lewis basic nature of nitrogen of the synthesized 2-Iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides enabled them as pre-catalyst for the activation of epoxide with CO2 at 1 atm for the preparation of cyclic carbonates with TOF and TON values of 1447 h-1 and 4343, respectively, under solvent-free conditions. In addition, 2-iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides have also been used as pre-catalyst for activating anilines and CO2 to form a variety of 1,3-diaryl ureas up to 95 % yield. The mechanistic investigation for CO2 mitigation is done by 125 Te NMR and HRMS studies. It seems that the reaction proceeds via formation of catalytically active Te-N heterocycle, an ebtellur intermediate which is isolated and structurally characterized.

Multistate Redox-Switchable Ion Transport Using Chalcogen-Bonding Anionophores

Synthetic supramolecular transmembrane anionophores have emerged as promising anticancer chemotherapeutics. However, key to their targeted application is achieving spatiotemporally controlled activity. Herein, we report a series of chalcogen-bonding diaryl tellurium-based transporters in which their anion binding potency and anionophoric activity are controlled through reversible redox cycling between Te oxidation states. This unprecedented in situ reversible multistate switching allows for switching between ON and OFF anion transport and is crucially achieved with biomimetic chemical redox couples.

Fast relaxing red and near-IR switchable azobenzenes with chalcogen and halogen substituents: periodic trends, tuneable thermal half-lives and chalcogen bonding

Molecular photoswitches operating in the red to near-IR region with controllable thermal relaxation rates are attractive components for photo-regulating biological processes. Herein, we report the synthesis of red-shifted azobenzenes functionalised with the heavier chalcogens and halogens that meet these requirements for biological application; namely fatigue-resistant photo-switching with red and near IR light and functional handles for further functionalisation for application. We report robust periodic trends for the chalcogen and halogen azobenzene series, and exploit intramolecular chalcogen bonding to tune and redshift the absorption maxima, supported by photo-physical measurements and solid-state structural analysis. Remarkably, the rate of the Z → E thermal isomerisation can be tuned over timescales spanning 107 s by judicious choice of chalcogen and halogen substituents.

Selective Potassium Chloride Recognition, Sensing, Extraction, and Transport Using a Chalcogen-Bonding Heteroditopic Receptor

Chalcogen bonding (ChB) is rapidly rising to prominence in supramolecular chemistry as a powerful sigma (σ)-hole-based noncovalent interaction, especially for applications in the field of molecular recognition. Recent studies have demonstrated ChB donor strength and potency to be remarkably sensitive to local electronic environments, including redox-switchable on/off anion binding and sensing capability. Influencing the unique electronic and geometric environment sensitivity of ChB interactions through simultaneous cobound metal cation recognition, herein, we present the first potassium chloride-selective heteroditopic ion-pair receptor. The direct conjugation of benzo-15-crown-5 ether (B15C5) appendages to Te centers in a bis-tellurotriazole framework facilitates alkali metal halide (MX) ion-pair binding through the formation of a cofacial intramolecular bis-B15C5 M⁺ (M⁺ = K⁺, Rb⁺, Cs⁺) sandwich complex and bidentate ChB···X^– formation. Extensive quantitative ¹H NMR ion-pair affinity titration experiments, solid–liquid and liquid–liquid extraction, and U-tube transport studies all demonstrate unprecedented KCl selectivity over all other group 1 metal chlorides. It is demonstrated that the origin of the receptor’s ion-pair binding cooperativity and KCl selectivity arises from an electronic polarization of the ChB donors induced by the cobound alkali metal cation. Importantly, the magnitude of this switch on Te-centered electrophilicity, and therefore anion-binding affinity, is shown to correlate with the inherent Lewis acidity of the alkali metal cation. Extensive computational DFT investigations corroborated the experimental alkali metal cation–anion ion-pair binding observations for halides and oxoanions.