First use of 1,4-dihydro-2,3-quinoxalinedione in the chemistry of coordination polymers: A 3D copper(II) complex containing the 2,3-dioxyquinoxalinate(−2) ligand in a novel coordination mode

The reaction of 1,4-dihydro-2,3-quinoxalinedione (H2L′) with CuCl2 in the presence of LiOH in DMF has led to the 3D coordination polymer [Cu3L2Cl2(DMF)4]n (1) with an (82 · 10)-a, lig (LiGe), topology, where L2− is 2,3-dioxyquinoxalinate(−2). This compound is the first coordination polymer of any transition metal featuring L2− and contains the ligand in a novel 3.1111 (Harris notation) coordination mode. IR data are discussed in terms of the chemical composition of the polymer and the coordination mode of L2−. Variable-temperature (2–300 K) magnetic susceptibility and variable-field (0–5 T) magnetization studies reveal that L2− propagates weak antiferromagnetic exchange interactions through its “quinoxaline” moiety.