Conformational control of benzyl-o-carboranylbenzene derivatives and molecular encapsulation of acetone in the dynamically formed space of 1,3,5-tris(2-benzyl-o-carboran-1-yl)benzene.
A 1,3,5-substituted benzene platform has been widely used in the fields of supramolecular chemistry and molecular recognition. Here, we show that 1,3,5-tris(2-benzyl-o-carboran-1-yl)benzene 6 exhibits solvent-dependent conformation in the crystalline state. Recrystallization from dichloromethane-n-pentane gave the anti conformation 6-anti, while recrystallization from methanol-acetone gave the syn conformation 6-syn, in which the three benzyl-o-carboranyl moieties are located to one side of the central benzene ring. Interestingly, one acetone molecule is captured in the π-rich space of 6-syn and two complexes facing each other encapsulate two acetone molecules in a π-rich container formed by the eight benzene rings. The inclusion involves several weak interactions, that is, T-shaped C-H···π interactions, and C-H···O and C-H···π interactions. Two C-H···O interactions involving benzylic C-H hydrogens activated by the electron-withdrawing character of the o-carborane cage and the oxygen atom of the acetone seem to be the most important. DFT calculations indicate that the binding energy for entrapment of acetone is 6.6 kcal/mol. Inclusion of acetone is achieved through not only multiple C-H···O interactions but also a number of C-H···π interactions. The third benzyl-o-carborane moiety is fixed in the syn conformation by intramolecular and intermolecular C-H···π interactions.
Faculty of Pharmaceutical Sciences, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
Chalermkiat
C
Songkram
Kiminori
K
Ohta
Kentaro
K
Yamaguchi
Fabio
F
Pichierri
Yasuyuki
Y
Endo
D000096:Acetone / Q000138:chemical synthesis / Q000737:chemistry*; D001555:Benzene Derivatives / Q000138:chemical synthesis / Q000737:chemistry*; D001593:Benzyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory
D001555:Benzene Derivatives; D001593:Benzyl Compounds; D001896:Boron Compounds; D000096:Acetone