Long-Range Ordered Magnet of a Charge-Transfer Ru₂⁴⁺/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.