Comparison of different synthetic approaches for the fabrication of a bio-inspired 1D-coordination polymer: From solution chemistry to mechanochemistry

Here we compare the effectiveness of three different synthetic approaches that we have applied to get a new coordination polymer (1) deriving from trans-ferulic acid (H2FA) and CoCl2⋅6H2O. The solvothermal reaction between the two reagents conducted in DMF for 6 days leads to X-ray-quality single crystals of 1, whose structural analysis revealed to correspond to the 1D-polymer [Co2(FA)Cl2(DMF)3]n. The yield of the reaction ranged from 24% to 52%, depending on the experimental conditions. The 1D-chains contain ferulate dianions bridging two different Co2+ cations, one octahedral and one tetrahedral. The same reaction conducted under reflux using H2FA or its ammonium salt (NH4)2FA leads to 1 but only in trace amounts (yield ≤ 11%). Complete conversion of the reagents to 1 was instead observed by grinding (NH4)2FA and CoCl2⋅6H2O by means of a planetary ball mills, already after 1 h of reaction. 1 turned out to be reactive towards moisture, with formation of the inorganic crystalline compound [CoCl2(H2O)4]⋅2H2O and a not yet defined amorphous phase that we tentatively formulate as [CoFA(H2O)x]n. Finally, the thermal behavior and magnetic properties of 1 are also reported.