Solvent Influence on Sizes of Channels in Three New Co(II) Complexes, Exhibiting an Active Replaceable Coordinated Site

Abstract

Three new 2D complexes were constructed by reaction of Co(NO3)2·6H2O with 4,4′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid (H3cpbda) in three different solvents (N,N′-dimethylformamide (DMF), N,N′-dimethylacetamide (DMA), and N-methylpyrrolidinone (DMP)), formulated as {[Co1.5(cpbda)(DMF)(H2O)3]·(DMF)}n (1), {[Co1.5(cpbda)(DMA)(H2O)3]·(DMA)}n (2), and {[Co1.5(cpbda)(DMP)(H2O)3]·(DMP)}n (3). Complexes were characterized by X-ray single-crystal diffraction, elemental analysis (EA), powder x-ray diffraction (PXRD), infrared spectra (IR), and thermogravimetric analysis (TGA). The solvents (DMF, DMA, and DMP) were incorporated in the final supramolecular structures, respectively, giving rise to three similar 2D frameworks. However, the special active replaceable coordination sites in the 1D channel were also discovered. The synthesis procedure was sensitive to small molecular carbonyl solvents (DMF, DMA, and DMP), but the hydroxy (methanol and alcohol) was not identified. The different coordinated and latticed solvent molecules in 1–3 propped up the varisized pore structures. By comparing the sizes of the 1D parallelogram channel in complexes 1–3, we found that the sizes of the channels (76.84 Å2 of 3 > 74.37 Å2 of 2 > 72.76 Å2 of 1) are induced by the sizes of the solvent molecules (DMP > DMA > DMF), and good chemical stability of 1–3 was observed. Magnetic susceptibility measurements indicated that complexes 1–3 exhibited antiferromagnetic coupling between adjacent Co(II) ions.