Unexpected “amphoteric” character of the halogen bond: the charge density study of the co-crystal of N-methylpyrazine iodide with I2Electronic supplementary information (ESI) available: Details of data collection, multipole refinement, and quantum chemical calculations. CCDC 764429. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c0cc01094d

An unexpected mechanism of halogen bonding that cannot be rationalized within the accepted σ-hole model was found in the co-crystal of N-methylpyrazine iodide with molecular iodine viathe topological analysis of the electron density distribution derived from the high-resolution X-ray diffraction data. [ABSTRACT FROM AUTHOR]