Diverse Structures and Ferro-/Ferri-/Antiferromagnetic Interactions of Pyridyltetrazole Coordination Polymers with Polycarboxylate Auxiliary Ligands.

Metal salts and 3/4-pyridyltetrazoles (3/4-Hptz) react with oxalic acid (H2ox), 1,2,4,5-benzenetetracarboxylic acid (H4btec), isophthalic acid (H2ip), and 1,2,3,4-butanetetracarboxylic acid (H4btca) to afford six coordination polymers, namely, [Cu(4-ptz)(ox)0.5]n (1), [Cu(4-Hptz)(btec)0.5]n (2), [Co2(3-ptz)(ip)(OH)(H2O)]n (3), {[Co1.5(3-ptz)(btca)0.5(H2O)]·H2O}n (4), {[Co3(4-ptz)2(btca)(H2O)3]·2H2O}n (5), and {[Cd2(4-ptz)2(btca)0.5(H2O)3]·DMF·4H2O}n (6). Their structures were characterized by EA, IR, PXRD, TGA, and single-crystal XRD. 3/4-Pyridyltetrazoles display μ2-, μ3-, and μ5-coordination modes in them. Complex 1 is a 3D MOF constructed from a 2D (4,4) [Cu(4-ptz)]n grid pillared by an oxalate spacer. Complex 2 displays a 2D network containing a square planar Cu1 and elongated octahedral Cu2 centers. Complex 3 shows a 2D network containing μ5-ptz, μ3-ip, and μ3-OH. Complex 4 exhibits a 3D MOF assembled by a 2D [Co1.5(btca)0.5]n network pillared by a 3-ptz spacer. Complex 5 displays a 3D porous MOF with nanosized rectangular tunnels. Complex 6 features a 3D porous MOF built by 2D [Cd2(4-ptz)(btca)0.5]n network pillared by a 4-ptz spacer. Variable-temperature magnetic susceptibility and magneto-structural correlation studies indicate that five CuII/CoII complexes present remarkable magnetic coupling diversity from ferro-, to ferri-, to antiferromagnetic interactions. Complex 1 shows strong antiferromagnetic behavior originating from the oxalate-bridging CuII dimer (Jox = −94.7 cm-1) and the tetrazole-bridging CuII dimer (Jptz = −61.0 cm-1). Complex 2 presents a weak ferromagnetic interaction (J = 0.82 cm-1) originating from the magnetic orbital orthogonality between square planar CuII and octahedral CuII centers. Complex 3 displays ferrimagnetic coupling in the Co3(μ3-OH) triangle. Two btca CoII complexes show antiferromagnetic interactions originating from carboxyl-bridging trinuclear CoII clusters with the θ values of −17.08 K for 4 and −8.6 K for 5. The thermal behaviors of these nitrogen-rich tetrazole complexes are investigated. Anhydrous complexes 1-3 containing rigid polycarboxylates are thermally stable to 250-300 °C and then decompose explosively, whereas complexes 4-6 with flexible butanetetracarboxylate decompose smoothly. [ABSTRACT FROM AUTHOR]