Tuning Cu II Coordination Polymers Derived from a Bis(pyrazolecarboxylate) Ligand by Solvothermal C–H Bond Activation: Synthesis, Structures, Catalysis, and Magnetic Properties

A new bis(pyrazolecarboxylate) ligand, 1,3‐phenylenebis(1 H ‐pyrazole‐5‐carboxylic acid) (H 2 PBPC) has been synthesized to study the structure and intriguing properties of the resultant coordination polymers synthesized under solvothermal conditions. The reaction of H 2 PBPC with Cu(ClO 4 ) 2 in the presence of NaOH at two different temperatures (80 and 120 °C) resulted in two coordination polymers, namely, [{Cu 2 Na(H 2 OPBPC)}] ∞ ( 1 ) and [{Cu 4 Na 2 (H 2 OPBPC) 2 }] ∞ ( 2 ), which display 2D corrugated sheet and 3D staircase architectures, respectively; in these structures, the aromatic C–H bond flanked by the pyrazolecarboxylate moieties was oxidized to form a C–O bond. When 2,2′‐bipyridine (2,2′‐bpy) was used instead of NaOH, [{Cu 2 (2,2′‐bpy) 2 (H 2 PBPC)}(H 2 O)] ∞ ( 3 ) formed, and such C–H bond activation was not observed. Interestingly, one of the coordination polymers, namely, 1 , displayed catecholase and phosphatase activity. Variable‐temperature magnetic susceptibility data in the range 2–300 K showed that there is antiferromagnetic coupling between the metal centers of 1 and 2 that is mediated through the phenoxo and pyrazole bridges, whereas 3 revealed dominant ferromagnetic interactions between the bis(pyrazolato)‐bridged Cu II centers owing to its very unusual Cu–N–N–Cu torsion angles of 75.28 and 69.52°.