Crystal Structures of Molecular Iodine Complexes with 1,2-bis(Pyridyl)Ethane and 1,2-bis(Pyridyl)Ethylene

The crystal structure of the molecular iodine complex with 1,2-bis(pyridyl)ethane is determined for the first time by the single crystal X-ray diffraction analysis and the structure of the molecular complex of iodine with 1,2-bis(pyridyl)ethylene is refined. It is shown that regardless of the initial ratio of reagents, only 2:1 complexes are formed in the systems in which ligands act as bridging ones and coordinate two iodine molecules with the formation of molecular complexes I₂LI₂. The structural and energy characteristics of gas phase complexes are calculated by DFT at the M06-2X/def2-TZVP level of theory. On passing from the gas phase to the condensed one, an enhancement of the donor-acceptor interaction is observed in the complexes, which shortens the N–I bond and elongates the I–I bond.