Crystalline Complexes of 2,2′-Bis(9-hydroxy-9-fluorenyl)biphenyl Host with Oligofunctional and Conjugate Functional Group Guests

Abstract

Four crystalline inclusion compounds of the 2,2′-bis(9-hydroxy-9-fluorenyl)biphenyl host 1, containing diethylene glycol (1:1) (1a), bis(2-aminoethyl)amine (1:1) (1b), methacrylic acid (1:1) (1c) and 2-cyclopenten-1-one (1:2) (1d), have been studied by X-ray diffraction analysis from single crystals. Departure from the expectation, the multifunctional and conjugate functional guest molecules, potentially being able to offer multiple H donor-/acceptorships or other modes of polar interaction due to the conjugation, do not result in the formation of infinitely connected networks in the crystal structures. Instead of this, discrete 2:2 host–guest aggregates (1a, 1b), guest dimers (1c) and rather conventional host–guest units (1d) are found. Hence, inherent shielding effects of the host molecule owing to the fluorenyl moieties and the presence of a strong intramolecular hydrogen bond, impeding multiple intermolecular association, are not overcome by the merits of the guest molecules, showing that the host compound 1 is superior by structural constancy in its crystalline inclusions.

Keywords:

• Inclusion host
• Organic guests
• Crystalline inclusion compounds
• Supramolecular interactions
• X-ray crystal structure determinations

Acknowledgements

K. S. and E. W. gratefully acknowledge the State Scholarships Foundation (IKY) and the German Academic Exchange Service (DAAD) for supporting this work by travel grant (IKYDA D/05/50689).