Long-range ordered magnet of a charge-transfer Ru₂ ⁴⁺/TCNQ two-dimensional network compound

Two isostructural 2D assemblies composed of [Ru₂(O₂CCF₃)₄] and TCNQ or TCNQF₄ in a 2:1 ratio were synthesized: [{Ru₂(O₂CCF₃)₄}₂TCNQ]·3(p-xylene) (1b) and [{Ru₂(O₂CCF₃)₄}₂TCNQF₄]·3(p-xylene) (2). In 1b, the TCNQ moiety is assigned to be neutral because of no significant electron transfer from the Ru₂⁴⁺ units. Therefore, the magnetic property of 1b can be understood to be a paramagnetic nature of the isolated Ru₂⁴⁺ unit, while, a fully charge-transfer from the Ru₂ units to the TCNQF₄ molecules in 2 leads to charge delocalization spreading over the 2D network and allows a long-range magnetic order to occur. On the basis of an idea of the resonance scheme in charge-transfer D₂A network systems, the first successful example of a charge-transferred magnet in the Ru₂-TCNQ system was rationally designed by tuning redox between [Ru₂]⁴⁺ and the TCNQ molecule changing from TCNQ to TCNQF₄.