Vapor Sorption and Solvatochromism in a Metal–Organic Framework of an Asymmetric Pyridylcarboxylate

Two new metal–organic frameworks (MOFs) of cobalt(II) and 3-(4-pyridyl)benzoate (34pba) were prepared concomitantly under solvothermal conditions. Using dimethylformamide (DMF) as solvent, {[Co(34pba) 2 (H 2 O)]·1/2DMF·H 2 O} n, 1, can be prepared as a pure phase in the presence of the templating molecules arginine or proline, neither of which is incorporated in the resulting structure. {[Co(34pba) 2 ]·2DMA} n, 2, (where DMA is dimethylacetamide) has the same framework formula as two previously reported MOFs and represents a third in this series of structural isomers. The activated phase of 1, 1d absorbs a number of solvent vapors, across a wide range of polarities, with accompanying phase changes and solvatochromic responses. The facile exchange of guest species within the framework of 1d is explained by the low activation energy (59–69 kJ mol –1 ) for the desorption of water from 1d · H 2 O .