Co₅/Co₈–Cluster-Based Coordination Polymers Showing High-Connected Self-Penetrating Networks: Syntheses, Crystal Structures, and Magnetic Properties

Two novel Co­(II)-cluster-based coordination polymersnamely, [Co5(μ3–OH)2(1,4-ndc)4(bix)2]n (1) and {[Co8(μ3–OH)4(1,4-ndc)6(btp)­(H2O)6]·H2O}n (2)were prepared by hydrothermal reactions of Co­(II) perchlorate with 1,4-naphthalenedicarboxylic acid (1,4-H2ndc) and different N-donor coligands (bix = 1,4-bis­(imidazol-1-ylmethyl)­benzene and btp = 4,4′-bis­(triazol-1-ylmethyl)­biphenyl). In 1, 10-connected [Co5(μ3–OH)2(COO)8] clusters are extended by the μ4-1,4-ndc2– and trans-bix ligands to construct a rare, self-penetrating ile framework that can interestingly be regarded as the cross-link of two interpenetrating 6-connected pcu networks. While for 2, [Co8(μ3–OH)4(COO)12] clusters serve as the 8-connected nodes, which are bridged by the μ4/μ5-1,4-ndc2‑ and trans-btp ligands to afford the highest-connected uninodal self-penetrating (420.68) network based on octacobalt clusters. A synthetic and structural comparison of 1 and 2 demonstrates that the features of auxiliary N-donor ligands play a key role in governing the in situ formed clusters and the final 3-D coordination frameworks. Magnetic susceptibility measurements indicate that complex 1 shows an antiferromagnetic interaction between the adjacent Co­(II) ions, whereas 2 displays the dominant antiferromagnetic exchanges in 300–50 K and a ferrimagnetic-like behavior at lower temperatures.