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 (H 2 L ). Coordination polymers based on trinuclear SBUs are {[Co 3 ( L ) 3 (py) 2 ](py)} n ( 1 ) and [Mn 3 ( L ) 3 (py) 2 (H 2 O) 2 ] n ( 4 ), and those based on dinuclear SBUs are {[Co 2 ( L ) 2 (py) 3 (H 2 O) 2 ](py)(CH 3 OH)} n ( 2 ), [Ni 2 ( L ) 2 (py) 4 (H 2 O)] n ( 3 ), {[Mn 2 ( L ) 2 (py) 3 (H 2 O) 2 ](py) 2 (CH 3 CH 2 OH)} n ( 5 ), {[Mn 2 ( L ) 2 (3-mpy) 4 (H 2 O)](CH 3 OH) 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 .