Preparation and magnetic properties of verdazyl-substituted dihydrophenazine radical cation tetrachloroferrate salts

New oxoverdazyl (Vz·)-substituted dihydrophenazine radical cations (DPP +) MCl 4 - (M = Ga, Fe) salts were prepared. The molecular and packing structures, the intramolecular exchange interactions, and the magnetic properties were investigated. The organic part (VzDPP +) showed a sizable intramolecular ferromagnetic interaction of J/kB ⩾ +250 K ( H = - 2 J S Vz · S DPP · + ) between Vz and DPP +, giving S = 1 state at room temperature. Both compounds had very similar molecular and packing structures and there were several intermolecular short contacts between the magnetically important atoms. A 2D type sheet structure was constructed through the contacts between VzDPP + and MCl 4 - moieties in the b–c∗ plane and a linear ladder chain structure was observed in the a∗-direction through the contacts between VzDPP + moieties. Thus, the overall intermolecular contacts extend in a 3D manner. The χpT value gradually decreased by lowering the temperature, indicating antiferromagnetic interactions in both salts. From the temperature dependence of χpT with consideration of the crystal packing structures, the antiferromagnetic interaction between the VzDPP + spins within the ladder chain was estimated to be in the order of −30 K for VzDPP + · GaCl 4 - . A similar antiferromagnetic interaction between the VzDPP + spins within the ladder chain and a slightly weaker antiferromagnetic interaction between the Fe(III) spins through the ladder chain were observed for VzDPP + · FeCl 4 - .