Paramagnetic Organic Co-crystals of Neutral or Ionic Radicals
Abstract
The formation of co-crystals from neutral radical species involves their association in a crystalline form with other neutral, eventually also radical, co-formers. We discuss these associations considering different situations where the radicals are either embedded within an inclusion compound, or stabilized through π-π interactions, hydrogen bonding or halogen bonding. Such associations in co-crystals can favor specific intermolecular interactions (and their associated magnetic response), which are not found in the pure radicals. This balance between dilution/isolation effects and control of the interaction dimensionality is one salient feature of these radical co-crystals. The strict definition of co-crystals has been further extended here to co-crystal salts, allowing for the introduction of cation (alt. anion) radical species such as those derived from the oxidation of tetrathiafulvalene derivatives (alt. the reduction of quinone derivatives), when associated in the crystal with the corresponding neutral molecules. Mixed-valence salts exhibiting full charge disproportionation (charge ordering) enter this last category. © The Royal Society of Chemistry 2018.