Stable heterotopic noncovalent resorcin[4]arene assemblies

Resorcin[4]arene tetracarboxylic acids 5,6 (A) and resorcin[4]arene tetrapy ridines 2,3 (P) self-assemble in chloroform solution to form stable heterot opic AP dimers. Data from NMR titration and dilution experiments, as well a s from vapor-pressure osmometry (VPO), indicate that the AP dimer is formed with an association constant greater than 10(7) M-1 Solid-solution extract ion experiments are indicative of the formation of a 2:1 trimer (A(2)P), wh ile self-associated homotopic species (A(2) and A(3)) can be detected by NM R and VPO. Analysis of the heterotopic noncovalent assembly process over a range of compositions shows that these other species are much less stable t han the AP heterodimer, which is the exclusive species at an A/P concentrat ion ratio of 1:1 (> 99.7% of the total at 10 mM).