Syntheses, Structures, and Magnetic Properties of Two Series of 3d–4f Heterometallic Coordination Polymers Derived from Pyrazine‐2,3‐dicarboxylic Acid

Twenty 3d–4f heterometallic coordination polymers (CPs), namely, [Ln 2 Co(2,3‐pzdc) 4 (H 2 O) 6 ] · 2H 2 O [Ln = La ( 1 ), Pr ( 2 ), Nd ( 3 ), Sm ( 4 ), Eu ( 5 ), Gd ( 6 ), Tb ( 7 )], [Ln 2 Co(2,3‐pzdc) 4 (H 2 O) 4 ] · 4H 2 O [Ln = Dy ( 8 ), Er ( 9 )], [Ln 2 Cu(2,3‐pzdc) 4 (H 2 O) 6 ] · 2H 2 O [Ln = La ( 10 ), Pr ( 11 ), Nd ( 12 ), Sm ( 13 ), Eu ( 14 ), Gd ( 15 ), Tb ( 16 )], [Dy 2 Cu(2,3‐pzdc) 4 (H 2 O) 4 ] · 4H 2 O ( 17 ), and [Ln 2 Cu(2,3‐pzdc) 4 (H 2 O) 4 ] · 2H 2 O [Ln = Er ( 18 ), Yb ( 19 ), Lu ( 20 )], are synthesized successfully by the reactions of 2,3‐H 2 pzdc with LnCl 3 · n H 2 O/Ln(NO 3 ) 3 · n H 2 O and Co(NO 3 ) 2 · 3H 2 O/CuCl 2 · 2H 2 O under hydrothermal conditions. CPs 1 – 20 are isostructural, and only the coordination and interstitial water molecules, as well as the coordination numbers of Ln III , are different from each other. In 1 – 20 , the 2,3‐pzdc anions link the Co II /Cu II and Ln III ions by two coordination modes to form a three‐dimensional (3D) framework with a 3,3,4,4‐connected (4 · 6 2 ) 2 (4 2 · 6 2 · 8 2 )(6 3 ) 2 (6 5 · 8) 2 topology. CPs 6 and 7 manifest the weak ferromagnetic interactions between Co II and Ln III in the low‐temperature range. CP 8 exhibits a field‐induced slow magnetic relaxation behavior. CP 16 shows a magnetic transition between short‐range ferromagnetic ordering at 60 K and long‐range ferromagnetic ordering below 26 K. CP 17 displays field‐induced single‐molecule magnet (SMM) behavior, with a U eff value of 102.4 K.