Thermo-and solvatochromic coordination networks of 4-(4-pyridyl)benzoic acid.

Abstract

Two novel metal-organic frameworks were synthetised solvothermally using the ditopic ligand: 4-(pyridin-4-yl)benzoic acid (44pba) (1) with either cobalt or nickel nitrate salts. Isostructural porous 3D-networks were obtained: [Co4(44pba)8]n. [(DMF)3•(EtOH)0.25•(H2O)4]n(2)and [Ni4(44pba)8]n.[(DMF)3.5•(EtOH)•(H2O)1.5]n(3). Their crystal structures were solved and their thermal behaviours studied. Both 2 and 3 displayed dramatic colour change when exposed to air and we owed that they readily absorb traces of water from the moist air. The reversibility of the water uptake and associated colour change were observed upon heating and fully characterised with hot stage microscopy (HSM- Figure 1), thermogravimetric analysis (TGA), Powder X-ray Diffraction (PXRD) and UV-Vis spectrometry.