An Experimental and Theoretical Insight into I₂/Br₂ Oxidation of Bis(pyridin-2-yl)Diselane and Ditellane

The reactivity between bis(pyridin-2-yl)diselane (Py2Se2)-Py-o and ditellane (Py2Te2)-Py-o (L1 and L2, respectively; Py-o=pyridyn-2-yl) and I-2/Br-2 is discussed. Single-crystal structure analysis revealed that the reaction of L1 with I-2 yielded [(HL1(+))(I-)& sdot;5/2I(2)](infinity) (1) in which monoprotonated cations HL1(+) template a self-assembled infinite pseudo-cubic polyiodide 3D-network, while the reaction with Br-2 yielded the dibromide (HPySeBr2)-Py-o-Br-II (2). The oxidation of L2 with I-2 and Br-2 yielded the compounds (HPyTeI2)-Py-o-I-II (3) and (HPyTeBr4)-Py-o-Br-IV (6), respectively, whose structures were elucidated by X-ray diffraction analysis. FT-Raman spectroscopy measurements are consistent with a 3c-4e description of all the X-Ch-X three-body systems (Ch=Se, Te; X=Br, I) in compounds 2, 3, (HPyTeBr2)-Py-o-Br-II (5), and 6. The structural and spectroscopic observations are supported by extensive theoretical calculations carried out at the DFT level that were employed to study the electronic structure of the investigated compounds, the thermodynamic aspects of their formation, and the role of noncovalent sigma-hole halogen and chalcogen bonds in the X & sdot;& sdot;& sdot;X, X & sdot;& sdot;& sdot;Ch and Ch & sdot;& sdot;& sdot;Ch interactions evidenced structurally.