Entanglement and Irreversible Structural Transformation in Co(II) Coordination Polymers Based on Isomeric Bis-pyridyl-bis-amide Ligands

Four coordination polymers constructed from the flexible isomeric bis-pyridyl-bis-amide (bpba) ligands, N,N′-di­(3-pyridyl)­suberoamide (L1) and N,N′-di­(4-pyridyl)­suberoamide (L2), and the auxiliary 1,4-naphthalenedicarboxylic acid (1,4-H2NDC), including [Co­(L1)1.5(1,4-NDC)­(H2O)]n, 1, [Co3(L1)1.5(1,4-NDC)3(EtOH)]n, 2, {[Co­(L2)1.5(1,4-NDC)]­·H2O}n, 3, and {[Co­(L2)0.5(1,4-NDC)]­·EtOH}n, 4, have been synthesized and structurally characterized by using single crystal X-ray crystallography. Complex 1 forms a two-dimensional layer with double edges and 2 exhibits a unique three-dimensional (3D) self-catenated framework with the (48.66.8)-6T60 topology, while 3 displays a 3D framework with the highest 5-fold interpenetration for the bnn topology and 4 shows a 3D 2-fold interpenetrated framework with the pcu topology. The donor atom positions of the L1 and L2 ligands and the identity of the solvents play important roles in determining the structural diversity. Moreover, irreversible structural transformation from 2 to 1 has been verified by immersing crystals of 2 into water. The coordination ability of the CH3CH2OH molecule in 2 and the thermal stability of 1 govern the irreversible structural transformation