A Series of Two-Dimensional Co(II), Mn(II), and Ni(II) Coordination Polymers with Di- or Trinuclear Secondary Building Units Constructed by 1,1′-Biphenyl-3,3′-Dicarboxylic Acid: Synthesis, Structures, and Magnetic Properties

Hydro/solvothermal and bilayered-diffusion methods using pyridine (py), 3-methylpyridine (3-mpy), and 4-methylpyridine (4-mpy) as weak bases and small terminal ligands generated seven Co-II, Mn-II, and Ni-II two-dimensional (2D) coordination polymers with di-, trinuclear metal clusters as secondary building units (SBUs) from an organic bridging ligand, 1,1'-biphenyl-3,3'-dicarboxylic acid (H2L). Coordination polymers based on trinuclear SBUs are {[Co-3(L)(3)(py)(2)](py)}(n) (1) and [Mn-3(L)(3)(py)(2)(H2O)(2)](n) (4), and those based on dinuclear SBUs are {[Co-2(L)(2)(py)(3)(H2O)(2)](py)(CH3OH)}(n) (2), [Ni-2(L)(2)(py)(4)(H2O)](n) (3), {[Mn-2(L)(2)(py)(3)(H2O)(2)](py)(2)(CH3CH2OH)}(n) (5), {[Mn-2(L)(2)(3-mpy)(4)(H2O)](CH3OH)(0.5)}(n) (6), and [Mn-2(L)(2)(4-mpy)(2)](n) (7). Further structural analysis indicates that 1, 4, and 7 have a (4,4) grid layered structure and 2, 3, 5, and 6 possess a (3,6) sheet structure. Magnetization studies show the existence of ferromagnetic coupling for 1 with a positive zJ value of 0.97 cm(-1), weak antiferromagnetic coupling for 2 (-E-2/k = -4.6 K), very weak antiferromagnetic coupling for 3 with a small negative J value of -0.17 cm(-1), weak or medium antiferromagnetic couplings for 4, 5, and 6 with the negative J values of -1.17, -1.53, and -1.62 cm(-1), respectively, and very strong antiferromagnetic coupling for 7 with a very large negative J value of -16.62 cm(-1).