The Solvent–Gelator Interaction as the Origin of Different Diffusivity Behavior of Diols in Gels Formed with Sugar-Based Low-Molecular-Mass Gelator

Organogels are soft materials consisting of low-molecular-mass gelators (LMOGs) self-assembled through noncovalent interactions into 3D structures, in which free spaces are filled by organic solvents. 4,6,4′,6′-<i>O</i>-terephthylidene-bis­(methyl-α-d-glucopyranoside) (<b>1</b>) is found to be a new LMOG. It gelatinizes only a limited number of solvents. Here, the gels of <b>1</b> with ethylene glycol (EG) and 1,3-propanediol (PG) are investigated with FT-IR, Raman, and UV–vis spectroscopies, the NMR relaxometry and diffusometry methods, and microscopic observation. The chemical structures of both solvents are closely related, but the variety of physical characteristics of the gels is large. The <b>1</b>/PG gels are thermally more stable compared to <b>1</b>/EG gels. The types of aggregates are most likely the H- and J-type in <b>1</b>/EG gels and the J-type in <b>1</b>/PG gels. Different microstructures are observed: bundles of crossing fibers for <b>1</b>/EG and a honeycomb-like matrix for <b>1</b>/PG gels. The diffusivity of the EG solvent in gels with <b>1</b> behaves as expected, decreasing with increasing gelator concentration, whereas the opposite behavior is observed for the PG solvent. This is a most fascinating result. To explain the diffusion enhancement, we suggest that a dynamic hydrogen bonding network of PG solvent in gel matrixes is disrupted due to solvent–gelator interaction. The direct proof of this interaction is given by the observed low frequency dispersion of the spin–lattice relaxation time of solvents in the gel matrixes

Proton Conducting Compound of Benzimidazole with Sebacic Acid: Structure, Molecular Dynamics, and Proton Conductivity

Benzimidazole salt of sebacic acid, a new proton conductor from the family of benzimidazole compounds of dicarboxylic acids, was crystallized to search for the factors which determine the hydrogen bond motif and the structure of the crystals. The molecular structure of benzimidazole-sebacic acid salt was solved by using X-ray diffractions and confirmed by ¹H and ¹³C MAS NMR experiments combined with DFT calculations. The salt of sebacic acid, with 10 carbon atoms in the chain, was found to exhibit an undulated layer-type structure with banana-shaped acid molecules linked by O–H···O bonds into rectangular-type wavy chains and flat base molecules attached to the carboxylic groups by N–H···O bonds. The undulated layers are not linked with hydrogen bonds. Comparison of the architecture of benzimidazole salts with weak dicarboxylic acids of shorter carbon chains, studied by us earlier, points at the role of the acid chain length in the formation of structural and hydrogen bond motifs. The dynamics of protons in the ordered crystalline phase and disordered surface layers was characterized by NMR spin–lattice relaxation measurements, whereas complex impedance studies yielded information on the activation energy of proton diffusion in the both phases

Proton Conducting Compound of Benzimidazole with Sebacic Acid: Structure, Molecular Dynamics, and Proton Conductivity

Benzimidazole salt of sebacic acid, a new proton conductor from the family of benzimidazole compounds of dicarboxylic acids, was crystallized to search for the factors which determine the hydrogen bond motif and the structure of the crystals. The molecular structure of benzimidazole-sebacic acid salt was solved by using X-ray diffractions and confirmed by ¹H and ¹³C MAS NMR experiments combined with DFT calculations. The salt of sebacic acid, with 10 carbon atoms in the chain, was found to exhibit an undulated layer-type structure with banana-shaped acid molecules linked by O–H···O bonds into rectangular-type wavy chains and flat base molecules attached to the carboxylic groups by N–H···O bonds. The undulated layers are not linked with hydrogen bonds. Comparison of the architecture of benzimidazole salts with weak dicarboxylic acids of shorter carbon chains, studied by us earlier, points at the role of the acid chain length in the formation of structural and hydrogen bond motifs. The dynamics of protons in the ordered crystalline phase and disordered surface layers was characterized by NMR spin–lattice relaxation measurements, whereas complex impedance studies yielded information on the activation energy of proton diffusion in the both phases