Iso-Tellurazolium-N-Phenoxides: A Family of Te···O Chalcogen-Bonding Supramolecular Building Blocks

Au-involving chalcogen bond in 4-(2-chalcophenyl)-1,2,3-triazolylidene Au(I) complexes: synthesis, characterization, and photophysical properties

Noncovalent interactions, particularly chalcogen bonds (ChBs), have gained prominence in modern chemistry due to their tunability and directionality. We present a pioneering investigation of a d10 metal-involving ChB in triazolylidene Au(I) complexes. The crystal structures reveal the occurrence of intramolecular ChBs between Au(I) and chalcophene substituents positioned on the wingtip of triazolylidene ligands. The strength of these ChB interactions can be effectively modulated by altering the chalcophene moieties and ancillary ligands associated with Au(I). The neutral LAu(I)X complexes exhibit remarkable phosphorescence, with photoluminescence quantum yield (PLQY) reaching up to 70% in the solid state, which is attributed to their rigid structure with intramolecular ChB interactions between the Au and chalcogen atoms. Moreover, density functional theory (DFT) calculations were performed to obtain insights into the nature of the ChB interactions.

Metal complexes featuring organotellurium ligands: synthesis, coordination behavior, and applications

Organotellurium ligand-facilitated metal structures are known for their catalytic activity, anti-cancer activities, and nanomaterial applications. A wide range of organotellurium ligands, including telluroethers, pincer-based frameworks, and tellurolates, have been extensively explored for their coordination with diverse metal centers. These ligands have been successfully complexed with base metals, platinum group metals, rare earth elements, and representative metals, providing a unified resource of literature on metal complexes of organotellurium ligands. The resulting metal-organotellurium complexes exhibit intriguing structural diversities and potential applications in catalysis, materials science, and coordination chemistry. A comprehensive review on various applications of organotellurium ligands has not been available since 2005. Moreover, within the broader field of chalcogen chemistry, organotellurium ligands remain relatively less explored. Hence, this review focuses on the synthetic strategies and various applications of metal complexes containing organotellurium ligands, addressing a significant and critical gap existing in the literature. This review provides a comprehensive analysis of organotellurium ligands, focusing on their synthesis, structural diversity, and coordination chemistry. Beyond their fundamental significance, these ligands play a vital role in life sciences, nanochemistry, and materials science. Their catalytic proficiency is evident in essential organic reactions, including the Suzuki-Miyaura and Mizoroki-Heck couplings, alcohol oxidation, C-N bond formation, aldehyde activation, and nitrophenol reduction.

Light-Induced Increase in Bond Strength─from Chalcogen Bond to Three-Electron σ Bond upon Excitation

Chalcogen bonds are σ hole interactions between a chalcogen center and a Lewis base center and have been applied in recent years as an alternative to hydrogen bonds in supramolecular chemistry and catalysis. While the electronic interactions of chalcogen bonds in the ground state have been intensively analyzed, there is barely any knowledge about the electron structure in the excited state. This is despite the fact that in some cases photoswitches containing chalcogen bonds exhibit exceptional switching behavior. Here, we investigate the effect of light absorption on chalcogen bonds containing divalent chalcogen centers. Quantum chemical calculations reveal that in the excited S1 state the noncovalent chalcogen bond converts to a covalent three-electron σ bond. The bond between the chalcogen center and the Lewis base center is thus significantly reinforced by light excitation. This change in bond type explains the previously experimentally observed nonswitchability of some tellurium-containing azo compounds. Furthermore, we were able to demonstrate that the switchability of certain selenium-containing compounds is temperature-dependent, whereby the ratio of the less stable cis compound is higher for higher temperatures. These results highlight the potential for designing responsive materials and dynamic molecular systems based on light-induced chalcogen bond modulation.

Using Rigidity and Conjugation of Subunits to Modulate Supramolecular Topologies Constructed by Half-Sandwich Fragments

The synthesis of supramolecular compounds with a high degree of controllability and the targeted modulation of their topological transitions pose significant challenges in situ. In this study, we have successfully constructed an array of discrete structures based on a series of bidentate pyridyl ligands (L1, L2, and L3), which were subsequently ligated with half-sandwiched (Cp*Ir fragments) building blocks. Our further investigations elucidate a strategy for coordinating the relative lengths of the bidentate ligands with the building blocks, achieving specific concentrations that drive the transformation of tetranuclear metal macrocycles into Borromean rings. Notably, the distinct characteristics of the three pyridyl ligands markedly influence the efficiency of synthesis and the topological conversion of the supramolecular macrocycles. Detailed structural analyses reveal that π-π stacking interactions, the electron-donating capabilities of the ligands, and hydrogen-bonding interactions are pivotal in stabilizing these molecular macrocycles and in facilitating their transformation to Borromean rings. The analyses underscore the importance of the electron-rich effect induced by the sulfur atoms in the ligands and the regulation and modulation of the pyridine functional group in contributing to the structural stability and altered characteristics of the macrocycles.

An Unusual Macrocyclic Hexamer of an Iso-Tellurazole N-Oxide Featuring CTe… O Chalcogen Bonds is Formed by κ6 -O Complexation to Fe(II) and Ni(II)

Studies of the supramolecular chemistry of iso-tellurazole N-oxides have been confined to non-polar media until now. To overcome that limitation, an iso-tellurazole N-oxide was derivatized with a primary alcohol group; the compound is soluble in polar solvents and stable in acidic to neutral aqueous media. Nickel (II) and iron (II) form macrocyclic complexes with six molecules of that iso-tellurazole N-oxide in a hitherto not-observed macrocyclic arrangement defined by CTe⋅⋅⋅O chalcogen bonds and κ6 -O bound to the metal ion. This behaviour is in sharp contrast with the κn -Te (n=1,2,4) complexes formed by soft metal ions.

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

The synthesis and characterisation of two novel molecular organotelluroxane clusters, comprising of an inorganic Te₈O₆X₄ (X = Cl, Br) core structure are described. The integration of highly electron withdrawing 3,5-bis-trifluoromethylphenyl groups to the constituent Te(IV) centres is determined to be crucial in the chalcogen bonding (ChB) halide template directed assembly. Characterised by multi-nuclear ¹H, ¹²⁵Te, ¹⁹F NMR, UV-Vis, IR spectroscopies and X-ray crystal structure analysis, the discrete molecular clusters exhibit excellent organic solvent solubility and remarkable chemical stability. Furthermore, preliminary fluorescence investigations reveal the telluroxanes exhibit aggregation induced emission (AIE) behaviour in organic aqueous solvent mixtures.

Unexpected ring closures leading to 2-N,N-dialkylaminoareno[1,3]tellurazoles

One step, up to 78% isolated yield, six examples. Facile access to 2-N,N-dialkylbenzo[1,3]tellurazoles.