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-ndc^2– 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-ndc^2‑ 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.