Host-guest chemistry of resorcinarenes-towards functional cavitands

Solid State and Structural Chemistry Unit, Indian Institute of Science
â—‹Tayur N Guru Row Mahalakshmi L. Partha Pratim Das

Design of functional materials via molecular recognition and self assembly is a topic of ongoing interest. Such studies on cavitands like resorcinarenes show the generation of novel supramolecular architecture stabilized by weak intermolecular interactions. In this context, we report our studies of the host molecule C-methylcalix[4]resorcinarene(1) with guest molecules 2,2-bipyridine(2), 1,4-diazabicyclooctane(3), coumarin(4), coumarin and 4,4-bipyridine (5). The compounds 2 and 4 crystallize in monoclinic system [C2/c, a=37.3084(43), b=12.7857(14), c=25.0057(29), β=131.496(2) and a=15.5206(21), b=14.4806(19), c=21.0803(29), β=109.378(2) respectively] whereas 3 crystallizes in a Tetragonal [P4(2)n), a=b=21.1519(10), c=15.7507(16)] and 5 in a Triclinic system[(P-1), a=12.0821(36), b=13.3291, c= 16.8730(50),α=93.197(5), β=100.739(5), γ=101.409(5)]. The conformation of the host molecule changes with the nature of the guest for e.g., in 1 and 2 the cone conformation is retained whereas in compounds 3 and 4 the host conformation changes to a partial cone or an open basket. Detailed structural analysis and nature of various intermolecular forces that constitute the packing modes in these complexes will be discussed.