A series of biphenyl methyl and ethyl diester derivatives of varying chain length (BBOn-R, Scheme 1) was synthesized and the gelation properties of the compounds were studied. The structures of these molecules were confirmed using <sup>1</sup>H and <sup>13</sup>C NMR spectroscopy. All of the compounds except for BBO6-Et and BBO7-Et form stable gels at 1.5% (wt/wt) in a variety of polar solvents. The modes of stacking and the nature of attractions between the gelator molecules were investigated using circular dichroism (CD), UV-Vis, and fluorescence spectroscopies. Scanning electron microscopy (SEM) was used for the investigation of the morphology of the xerogels. All of the gels obtained in octanol showed a typical entangled twisted ribbon-like structure. Gelation was found to be dependent upon temperature of formation, physical disruptions, rate of formation, and structure of the gelator. XRD analyses of the xerogels reveal that all of they have similar structural features. The solid-state structures of BBO6-Et and BBO6-Me were determed by X-Ray crystallography. The strengths of the intermolecular interactions in these isostructural compounds were explored in an effort to understand why the methyl ester is a gelator, but the ethyl ester is not under the conditions explored. An examination of the supramolecular structure and differences in intermolecular interaction energies provide a possible reason for the difference in gelation ability.

Effect of chain length on gelation ability of several biphenyl long-chain diesters

255th National Meeting (2018)

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