Bicyclo[2.2.2]octene-Based “Crab-like” Molecules: Synthesis, Complexation, Luminescence Properties, and Solid-State Structures

The U-shaped, multifunctionalized tetraetheno-bridged dicyclopenta[b,i]anthracenediol 10 was
synthesized to serve as a platform molecule. The molecule was prepared from the Diels−Alder
adduct 5a of tricycloundecatriene 3 and bicyclo[2.2.2]octene-fused p-benzoquinone 4. Functionalization of 10 to construct crab-like molecules was achieved via the base-promoted bis-O-alkylation
of two endo-oriented hydroxyl groups at termini in 10 with the following alkyl halides:  allyl,
propagyl, and benzyl bromides; 1-bromo- and 1-iodo-4-(bromomethyl)benzene; 9-(bromomethyl)anthracene; 1-(bromomethyl)pyrene; and isomeric bromomethylpyridines. Single-crystal X-ray
structures were obtained for bis-phenyl (21) and bis-pyrenyl (25) crabs, and for the silver(I) complex
(32 and 33) crabs. The silver(I) complex 32 from bis-o-pyridyl crab 30 is a [2+2] dimeric
dimetallocyclophane, and 33 from bis-m-pyridyl crab 29 is a [1+1] metallo-bridged cyclophane.
The self-assembled intramolecular π-stacking of pyrenyl rings in 25 with an interplanar distance
of 3.40 Å and the consequent π−π interactions were revealed by the X-ray crystal structure and its
luminescence property.