Cyclohexanone-Driven Discriminatory Behavior Change of Host Compound (+)-(2R,3R)-TETROL for Isomeric Methylcyclohexanone Guests

Abstract

Using appropriate competition experiments, host compound TETROL [(+)-(2R,3R)-1,1–4,4-tetraphenylbutane-1,2,3,4-tetraol] was revealed to discriminate between the isomeric methylcyclohexanone guests; the host selectivity was in the order 2- ≫ 3- > 4- methylcyclohexanone. Surprisingly, addition of unsubstituted cyclohexanone to these competitions instigated a complete reversal in the host’s preference for the alkylcyclohexanones: a selectivity order of cyclohexanone >4- > 3- > 2-methylcyclohexanone was attained. It is proposed that it is the significant preference of TETROL for cyclohexanone that is responsible for the host behavior change in the presence of this guest. As evidence, the crystal packing of a mixed complex, TETROL·(72%)­cyclohexanone·(28%)­4-methylcyclohexanone, was shown to be isostructural with pure TETROL·cyclohexanone (which differs from TETROL·4-methylcyclohexanone). The addition of cyclohexanone to the competition experiments therefore steers crystallization toward crystals with similar packing to that of the preferred guest complex accounting for TETROL’s change in selectivity in the presence of this guest. Hirshfeld surface analyses were used to demonstrate that TETROL·cyclohexanone experiences a significantly larger number of stabilizing O···H/H···O interactions (15.2%) compared with the other complexes (11.5–14.4%), accounting for the host’s overwhelming preference for this guest. Thermogravimetric analysis further confirmed that cyclohexanone was more strongly bound in the crystal than the other guests.

Mechanistic Consideration for the Selective Inclusion of Disubstituted Benzene Isomers with p-tert-Butylcalix[4]arene Crystals

“…To clarify the difference in the CH−π interactions in the inclusion crystal, we performed Hirshfeld surface analyses for 1 2 · o -xylene, 1 2 · m -xylene, and 1 2 · p -xylene using the CrystalExplorer 17 program . This analysis is useful for evaluating the origin of the packing structure and structure of inclusion complexes constructed by host and guest molecules. − Hirshfeld surfaces of a guest molecule in each inclusion crystal are shown in Figure a–c. The two-dimensional fingerprint plots for each Hirshfeld surface, where d e and d i are distances to the nearest atom outside and inside the surface, respectively, are shown in Figure d–f.…”

Structure analysis of inclusion crystals of diimide-based macrocycles with halocarbons

“…28–30 Diimide-based macrocycles are expected to be suitable hosts because their oxygen atoms and electron-deficient π–surfaces may engage in the complexation with halocarbons. 31–33 In this study, we showed that three diimide-based macrocycles containing adamantane parts were valuable and accessible hosts for the uptake of several liquid halocarbons. Crystals 1a with iodomethane and 1b with 1,2-dibromoethane were constructed from macrocycle ( 1 ) possessing PMDI units.…”

“…The importance of designing and preparing crystalline materials containing liquid organic compounds has become apparent over the last few decades in relation to the structural elucidation of the included guest molecules and the purification and separation of specific compounds from isomeric mixtures through selective molecular recognition by diverse non-covalent interactions. [1][2][3][4][5][6] Macrocyclic compounds are useful hosts for the encapsulation of a wide variety of guest molecules by solution crystallization, which is a simple and low-cost process. [7][8][9] Many molecules including alkanes, alcohols, ethers, amines, and aromatics have been employed as guests.…”

Hydrogen Bonding, the Driving Force for Increased Host Selectivities in Two-Solvent Mixed Complexes of TETROL Comprising Both Favored (Aniline) and Disfavored Guests (o-Toluidine or Toluene)

“…9,10 Competition studies with these guests demonstrated that in the absence of cyclohexanone, the host selectivity order was 2-≫ 3-> 4-methylcyclohexanone; however, as soon as unsubstituted cyclohexanone was added to the competitions, it instigated a complete reversal in this order (cyclohexanone > 4-> 3-> 2-methylcyclohexanones). 11 A dimethoxy derivative of TETROL also displayed host ability and behaved preferentially when recrystallized from mixed xylenes. 12 In the present work, we have assessed its host ability in the presence of guests aniline (ANI), o-, m-and p-toluidine (oTOL, mTOL, and pTOL, respectively), and toluene (TOL) (Scheme 1).…”

“…It has the potential to behave as a host material for the separation of the methylpyridines . Cyclohexanone and the isomeric methylcyclohexanones also formed complexes with this host and, surprisingly, the 3- and 4-methyl derivatives were enclathrated as their least stable axial conformers. , Competition studies with these guests demonstrated that in the absence of cyclohexanone, the host selectivity order was 2- ≫ 3- > 4- methylcyclohexanone; however, as soon as unsubstituted cyclohexanone was added to the competitions, it instigated a complete reversal in this order (cyclohexanone > 4- > 3- > 2- methylcyclohexanones) . A dimethoxy derivative of TETROL also displayed host ability and behaved preferentially when recrystallized from mixed xylenes .…”