Topological investigation on the structural diversity of Co(II) coordination polymers with mixed ligands: Effect of ligand isomerism and substituent

Abstract

Co(II) coordination polymers constructed from the isomeric N,N’-bis(3-pyridylmethyl)oxalamide (L1) and N,N’-bis(4-pyridylmethyl)oxalamide (L2) and polycarboxylic acids with different substituents at the 5th positions of the phenyl rings are reported, including {[Co(L1)(1,3,5-HBTC)]·H2O}n (1,3,5-H3BTC = benzene-1,3,5-tricarboxylic acid), 1, {[Co(L1)(5‑tert-IPA)(H2O)2]·H2O}n (5‑tert-H2IPA = 5‑tert-butylbenzene-1,3-dicarboxylic acid), 2, [Co(L1)0.5(5-NH2-IPA)(H2O)]n (5-NH2H2IPA = 5-aminoisophthalic acid), 3, {[Co2(L2)2(1,3,5-HBTC)2]·(L2)·5H2O}n, 4, {[Co(L2)1.5(1,3,5-HBTC)]·2H2O}n, 5, {[Co(L2)(5‑tert-IPA)]·H2O}n, 6, {[Co(L2)(5-NH2-IPA)(H2O)]·2·5H2O}n, 7, {[Co(L2)(5-NH2-IPA)]·4H2O}n, 8. Complexes 1, 3, 5 and 6 are 2D nets with the 3,5L2, bey, bey, 3,5L2 topologies, and 2 is a 3-fold interpenetrated 2D net with the hcb topology, whereas 4 is a 3D framework with the pcu topology, 7 is a self-catenated 3D net with the 3,5T48 topology and 8 is a 3-fold interpenetrated 3D net with the 3,5T1 topology, respectively. While the solvent system and energy are important in the preparation of Co(II) coordination polymers, the ligand isomerism of the neutral spacer ligand and the identity of the substituent group of the polycarboxylate ligand govern the structural diversity.