Series of Single-Ion and 1D Chain Complexes Based on Quinolinic Derivative: Synthesis, Crystal Structures, HF-EPR, and Magnetic Properties

By utilizing the quinolinic derivative, 8-carboxymethoxy-2-carboxylicquinoline (L), five transition metal coordination complexes, [M­(L)­(H2O)3]·H2O] (M = Mn (1), Co (2)), [Ni­(L)­(H2O)2] (3), and {[M­(L)]­(H2O)} n (M = Ni (4), Cu (5)), were synthesized by hydrothermal methods employing similar synthetic strategies. The crystal structures, magnetism and high-field EPR were characterized for the obtained compounds. 1–3 are mononuclear compounds. 1 and 2 have pentagonal bipyramidal geometry, while 4 and 5 exhibit one-dimensional zig-zag chain. Direct current magnetic and EPR studies demonstrate that compound 2 has large and positive D value (∼70.4 cm–1), indicating the easy plane magnetic anisotropies of 2. This D value is the largest one in the reported Co­(II) complexes with pentagonal bipyramidal geometry. Field-induced slow magnetic relaxation behavior was observed for 2 by the dynamic ac magnetic susceptibility measurements. The dc magnetic susceptibility studies of 4 and 5 give similar weak MII–MII antiferromagnetic interactions (J = −1.50 and −3.55 K for 4 and 5, respectively). High-field EPR results show that 4 can be considered as a quantum antiferromagnet.