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

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.