Structures and Gelation Properties of a Series of Salts Derived from an Alicyclic Dicarboxylic Acid and n-Alkyl Primary Amines

Structures and the gelation property of a series of primary ammonium hydrogen dicarboxylate salts derived from cyclobutane-1,1-dicarboxylic acid and n-alkyl amines, that is, Me-(CH₂)_n-NH₂ (n = 3−15, reacted in 1:1 molar ratio) have been studied systematically as a function of alkyl chain length. While salts with n < 11 did not show any gelation ability, salts with n > 11 could gel a number of solvents including commercial fuels such as kerosene. On the basis of the single crystal, powder X-ray diffraction and data from various microscopies (scanning electron and optical microscopy), a structure−property correlation has been attempted. The results revealed that a two-dimensional hydrogen bonding network and nearly identical crystal packing are present in the crystal structures of the salts (n = 3, 8−15) reported herein displaying the inability of imparting hydrogen bond isomerism because of alkyl−alkyl interactions. Existence of microcrystals of thin plate like morphology directly obtained from gel as well as dilute solution demonstrated the meta-stable nature of the gel forming network.