Synthesis and Supramolecular Behaviour of 2,7-Dibromo-9-alkynylfluorenols

Abstract

Two host compounds 2,7-dibromo-9-ethynyl-9-fluorenol (1) and 2,7-dibromo-9-trimethylsilylethynyl-9-fluorenol (2) were synthesized and their inclusion properties studied. Crystals of the host compounds show interesting change of colour from yellow to colourless upon guest complexation. To determine this phenomenon the crystal structures of guest-free compounds and five selected clathrates, involving diethylamine, triethylamine, pyridine, and 1,4-dioxane as the guest, have been determined by X-ray diffraction. The various modes of supramolecular interaction observed in these crystals are used as a basis for explaining colour changes accompanying guest inclusion.

Keywords:

• 9-Alkynyl-9-fluorenols
• Crystalline inclusion compounds
• Organic guests
• Decolouration phenomenon
• Supramolecular interactions
• X-ray crystal structure determinations

Acknowledgements

R.H. is grateful for a Georg Forster Scholarship from Alexander von Humboldt Foundation. T.S. thanks the Research Council of Mazandaran University for their partial financial support.