Successive magnetic ordering in two CoII-ladder metal-organic frameworks

Abstract

Metal-organic frameworks showing successive magnetic ordering are far less common than inorganic compounds. Here, we report two metal-organic frameworks [CoII(ox)(bphy)•0.1(DMF)•0.1(MeOH)] n ( 1 ) and [CoII3(ox)3(bphy)2(DMF)2] n ( 2 ) comprised of zigzag and necklace CoII-ladders, respectively. Together with a previously reported compound [CoII(ox)(bphy)•0.2(DMF)] n ( 3 ) consisting of spiraling zigzag CoII-ladders, these three compounds provide a good system for comparative structural and magnetic studies. Comprehensive magnetic analysis reveals that the three compounds undergo long-range magnetic ordering at ~2.6 K but exhibit vastly different short-range magnetic correlations: compound 1 shows short-range spin-canted antiferromagnetism ordering at ~14.0 K; compound 2 demonstrates successive short-range antiferromagnetism ordering at ~15.5 and ~12.6 K; compound 3 shows slow magnetic relaxation with T b≈ 4.6 K. These results demonstrate long-range magnetic ordering is readily accessible in the frameworks of ox2− bridging CoII-ladders linked by bphy, where short-range magnetic correlations can be systematicly tuned by the CoII-ladder structures.