C—I...NC halogen bonding in two polymorphs of the mixed-valence 2:1 charge-transfer salt (EDT-TTF-I₂)₂(TCNQF₄), with segregated versus alternated stacks

Two polymorphs of the 2:1 charge-transfer salt (EDT-TTF-I₂)₂(TCNQF₄) illustrate the two main modes of solid-state organization of π-type radical species, either in extended delocalized chains with the possibility for conductivity, or into dimeric or tetrameric units with localized bonding interactions.