NEW CRYSTALLINE HOSTS BASED ON TARTARIC ACID - SYNTHESIS, INCLUSION PROPERTIES, AND X-RAY STRUCTURAL CHARACTERIZATION OF INTERACTION MODES WITH ALCOHOL GUESTS

A series of host molecules derived from tartaric acid have been synthesized in optically resolved and racemic forms. Apart from two endo hydroxyl functions and four bulky aromatic groups (TADDOL-type = alpha,alpha,alpha',alpha'-tetraphenyl-1,3-dioxolane-4,5-dimethanols), they have specific polar and apolar substituents of different size, in different number, and in different positions laterally attached to the molecular framework as the characteristic features. These hosts form crystalline inclusion compounds with uncharged organic molecules ranging from protic dipolar (alcohols, amines) to apolar compounds (in all 143 different inclusion species). Inclusion formation, host:guest stoichiometric ratios, and interaction modes depend on the structural features of the host, as supported by X-ray crystallographic studies in nine cases involving MeOH, EtOH, and 2-PrOH. The optically resolved host species with Me and F substituents form linear (spiral) host-guest H-bonded chains in compounds containing MeOH guests, circular motifs of H-bonds in crystals consisting of the racemic host species, while in the presence of larger guest alcohols (2-PrOH) a finite noncyclic H-bonded cluster occurs with the chiral constituents. The crystal packings in structures involving the tetrachloro-substituted hosts and MeOH as guest are dominated by specific Cl...Cl nonbonding interactions which create interhost voids sufficiently large to accommodate a cluster of three H-bonded MeOH moieties. The packing structure of inclusion compounds containing fluoro substituted hosts are stabilized by CH(phenyl)...F interactions.