1,1'-Binaphthyl-2,2'-dicarboxylic acid (1) is demonstrated as a novel type of clathrate host whose main mode of action is derived from a combination of the steric barrier and the coordinative interaction principle which constitutes the new “coordinatoclathrate” strategy. Inclusion properties of the crystal lattice of 1 are revealed for a variety of uncharged organic guest molecules (30 examples), ranging from OH-, to NH-, to CH-acidic compounds such as alcohols, carboxylic acids, amides, and nitriles to rather unpolar compounds like bromobenzene and toluene. Marked discrimination selectivities in the clathrate formation from solvent mixtures are found in regard to the group functionality, the substitution pattern, and the molecular size of the guest species, making accessible a simple process for chemical compound separation. The stoichiometries and the increased-temperature as well as the reduced-pressure stabilities of the various clathrates are discussed. The principles of structure of five different alcohol clathrates of 1 are determined with the aid of X-ray structure analysis at 273 K: l⋅2MeOH (10) [P21/n, a = 15.642 Å, b = 14.532 Å, c = 9.292 Å, β = 95.14°, Z = 4]; l⋅2EtOH (11) [C2/c,a= 11.737 Å, b = 14.522 Å, c = 13.769 Å, β = 101.5°, Z = 4]; l-2(2-PrOH) (13) [C2/c, a = 12.051 k, b= 14.776 Å, c = 14.362 Å, β = 102.53°, Z = 4]; 1⋅2-BuOH (15) [P21/n, a = 12.009 Å, b = 12.747 Å, c = 14.982 Å, β = 105.52°, Z = 4]; 1-ethylene glycol (24) [P21/n, a = 14.276 Å, b = 9.533 Å, c = 15.556 Å, β = 109.19°, Z = 4], In all these cases, however, hydroxyl groups of the host molecules were found to be intercalated via large pseudo-ring formation between the carboxyl functions of at least two host units of opposite chirality with a different mode of hydrogen bridging. Depending on the hostiguest stoichiometry (1:1 or 1:2) and on the nature of the guest molecules, these entities consist of three, four, or eight moieties (COOH, OH). The direction of the strong and cooperative bonds is always homodromic. The shape and the size of the cleft formed in the matrix of cooperating host moieties are shown to vary, matching the specific needs of coordinating interactions (hydrogen bonding) and topological requirements (branching, e.g.) of the guest species.
ASJC Scopus subject areas
- Colloid and Surface Chemistry