Methanol mediated crystal transformations in a solvatochromic metal organic framework constructed from Co(II) and 4-(4-pyridyl) benzoate

The structural transformations of compound 1 {[Co(44pba)(2)](4)center dot(DMF)(3)center dot(EtOH)(0.25)center dot(H2O)(4)}n [44pba = 4-(4-pyridyl) benzoate] were followed during the exchange of DMF and ethanol molecules by methanol at room temperature. The new phases obtained 2 {[Co(44pba)2]center dot(MeOH)2.5 center dot(H2O)}n, 3 {[Co(44pba)(2)(MeOH)(2)](2)center dot(MeOH)(2.5)center dot(H2O)(2)} n and 4 {[Co(44pba)(2)(MeOH)(2)]center dot(MeOH)(0.5)center dot(H2O)(0.5)}(n) were studied using differential scanning calorimetry, thermogravimetric analysis and X- ray diffraction methods. The final phase 4 reverts back to 1 upon soaking 4 in a dry DMF-ethanol mixture as evidenced by the powder diffraction data and infrared spectra.