The cocrystallization of 1,2,5-chalcogenadiazoles (chalcogen E = S, Se, and Te) with cyclic polyethers 18-crown-6 (18-c-6) and dibenzo-18-crown-6 (db-18c-6) yielded the molecular complexes characterized by X-ray diffraction and thermogravimetry/differential scanning calorimetry techniques together with density functional theory (DFT) calculations and quantum theory of atoms in molecule and natural bond orbitals analysis. The complexes are bound by multiple secondary bonding interactions, the most important of which reflects the Lewis ambiphilicity of 1,2,5-chalcogenadiazoles and includes charge transfer from O atoms of the ethers onto E atoms of the chalcogenadiazoles (i.e., chalcogen bonding), and the back-donation from E to O. For complexes of 18-c-6, the DFT-calculated energies of bonding interactions correlate with the melting temperatures of the complexes, as well as with the atomic number of E and the size of the E-associated σ-holes but not with the maximum of molecular electrostatic potential at the σ-holes. Taking into account the previous results, the Lewis ambiphilicity of 1,2,5-chalcogenadiazoles may be used for applications in crystal engineering.

New complexes of 5,6-dicyano[1,2,5]selenadiazolo[3,4-b]pyrazine 1 with halide anions X– (X = Cl, Br, I) are prepared. With XRD, DFT, QTAIM and NBO, it is found that the complexes are formed...

A new electron acceptor is synthesized and reduced into its radical-anion isolated in the form of two salts with different structures and magnetic properties.

2,1,3‐Benzochalcogenadiazoles C6R4N2E (E/R; E=S, Se, Te; R=H, F, Cl, Br, I) and C6H2R2N2E (E/R’; E=S, Se, Te; R=Br, I) are 10π‐electron hetarenes. By CV/EPR measurements, DFT calculations, and QTAIM and ELI‐D analyses, it is shown that their molecular electron affinities (EAs) increase with decreasing Allen electronegativities and electron affinities of the E and non‐hydrogen R (except Cl) atoms. DFT calculations for E/R+e⋅−→[E/R]⋅− electron capture reveal negative ΔG values numerically increasing with increasing atomic numbers of the E and R atoms; positive ΔS has a minor influence. It is suggested that the EA increase is caused by more effective charge/spin delocalization in the radical anions of heavier derivatives due to contributions from diffuse (a real‐space expanded) p‐AOs of the heavier E and R atoms; and that this counterintuitive effect might be of the general character.