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.