Sodium chains as core nanowires for gelation of organic solvents from a functionalized nicotinic acid and its sodium salt

A new metallo-organic gelator formed from an admixture of a substituted nicotinic acid and its sodium salt is described. The nicotinic acid is substituted in the 6-position by an acetal functionality. The crystal structure of the 1:1 mixture revealed that the sodium atoms are aligned in infinite chains with the two organic units hydrogen bonded together to create potentially trinucleating ligands that encase the metal core, which leads to tube-like structures. These one-dimensional crystals were found to spontaneously gelify dichloromethane and provide pyridine gels with high thermal resistance. Gel formation was investigated by several analytical techniques, which included differential scanning calorimetry, TEM, freeze fracture electron microscopy (FFEM), IR spectroscopy and X-ray diffraction, and was found to be induced by the swelling of the one-dimensional material. FFEM and powder X-ray diffraction have revealed that the sodium chains are associated in a highly compacted state into a layered structure inside the gel. Doping these robust gels with dyes by diffusion, such as xylene cyanol, methyl yellow and bromo thymol blue, is feasible without destruction of the gels.