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, [Co-5(mu(3)-OH)(2)(1,4-ndc)(4)(bix)(2)](n) (1) and {[Co-8(mu(3)-OH)(4)(1,4-ndc)(6)(btp)(H2O)(6)]center dot H2O}(n) (2)-were prepared by hydrothermal reactions of Co(II) perchlorate with 1,4-naphthalenedicarboxylic acid (1,4-H(2)ndc) 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 [Co-5(mu(3)-OH)(2)(COO)(8)] clusters are extended by the mu(4)-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, [Co-8(mu(3)-OH)(4)(COO)(12)] clusters serve as the 8-connected nodes, which are bridged by the mu(4)/mu(5)-1,4-ndc2- and trans-btp ligands to afford the highest-connected uninodal self-penetrating (4(20).6(8)) 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.