Molecular Nuances Governing the Self-Assembly of 1,3:2,4-Dibenzylidene-d-sorbitol

1,3:2,4-Dibenzylidene-D-sorbitol (DBS) is the gold-standard for low-molecular-weight organogelators (LMOGs). DBS gels a wide array of solvents, as illustrated by the large Hansen sphere representing gels (2 delta(d) = 33.5 MPa1/2, delta(p) = 725 MPa1/2, and delta(h) = 8.7 MPa1/2; radius = 11.2 MPa1/2). Derivatives of DBS have been synthesized to isolate and determine molecular features essential for organogelation. In this work, pi-pi Stacking and hydrogen bonding are the major noncovalent interactions examined. The importance of pi-pi stacking was studied using 1,3:2,4 dicyclohexanecarbox-ylidene-D-sorbitol (DCHS), which eliminates possible pi-pi stacking while still conserving the other structural aspects of DBS. The replacement of the benzyl groups with cyclohexyl groups led to a very a poor gelator; only one of the several solvents examined, carbon tetrachloride, formed a gel. 1,3:2,4-Diethylidene-D-sorbitol (DES), another DBS analogue incapable of pi-pi stacking but with very different polarity, gelated a large Hansen space (2 delta(d) = 34.0 MPa1/2, delta(p) = 10.9 MPa1/2, and delta(h), = 10.8 MPa1/2; radius = 9.2 MPa1/2). DES gels solvents with higher delta(p) and delta(h) values than DBS. To assess the role of hydrogen bonding, DBS was acetalated (A-DBS), and it was found that the Hansen space gelated by A-DBS shifted to less polar solvents with higher hydrogen-bonding Hansen solubility parameters (HSPs) (2 delta(d) = 33.8 MPa1/2, delta(p) = 6.3 MPa1/2, and delta(h) = 9.6 MPa1/2; radius = 11.1 MPa1/2) than for DBS. These systematic structural modifications are the first step in exploring how specific intermolecular features alter aspects of Hansen space corresponding to positive gelation outcomes.