Molecular recognition of anionic substrates. Crystal structures of the supramolecular inclusion complexes of terephthalate and isophthalate dianions with a bis-intercaland receptor molecule

Molecular recognition of flat substrates requires the design of receptor mo lecules containing complementary flat units. If two such units are incorpor ated into a macrocyclic framework, a face to face inclusion of a planar sub strate may take place, leading to an intercalative supramolecular structure . The water-soluble macrocyclic bis-intercaland receptor 1.4H(+), containin g two naphthalene subunits, linked by two positively charged oxy-bis-ethyla mine binding sites, is able to bind strongly Bat organic anions. The crysta l structures of the terephthalate 2 and isophthalate 3 inclusion complexes are reported here. Complex 2, triclinic, P-I(N degrees 2), a = 7.717(3), b = 10.625(6), 16.238(9) A, alpha = 99.00(7), beta = 99.70(6), gamma = 109.46 (4)degrees, Z = 1. Complex 3, triclinic, PI (N degrees 1), a = 7.513(10), b = 10.640(9), c = 16.164(10) A, alpha = 98.81(5), beta = 99.77(10), gamma = 109.36(12)degrees, Z = 1. Comparison of the environment (water molecules, anions and macrocycle) in the two X-ray structures highlights the formation of a similar organized assembly with the two different substrates.